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TWI772930B - Analysis filter bank and computing procedure thereof, analysis filter bank based signal processing system and procedure suitable for real-time applications

Publication number

TWI772930B

TWI772930B TW109136460A TW109136460A TWI772930B TW I772930 B TWI772930 B TW I772930B TW 109136460 A TW109136460 A TW 109136460A TW 109136460 A TW109136460 A TW 109136460A TW I772930 B TWI772930 B TW I772930B

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TW

Taiwan

Prior art keywords

sub

filter bank

analysis filter

band

subband

Prior art date

2020-10-21

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• Radar Systems Or Details Thereof (AREA)
• Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
• Image Processing (AREA)
• Compression, Expansion, Code Conversion, And Decoders (AREA)

An analysis filter bank corresponding to a plurality of sub-bands which performs a frequency division filtering on an input signal to generate a plurality of sub-band signals, where the sub-bands are with equal width, the analysis filter bank comprises: a sub-band response pre-compensating device which performs a linear filtering on the input signal to generate a response pre-compensating signal, a plurality of sub-filters with different central frequencies which perform a complex-type first-order infinite impulse response filtering on the response pre-compensating signal separately to generate a plurality of sub-filter signals, and a plurality of binomial combining and rotating devices based on a set of binomial weights, each performs a weighted-sum operation on at least two sub-filter signals with the set of binomial weights, and rotates the weighted-sum value with a phase according to the corresponding sub-band central frequency to generate a sub-band signal of a plurality of sub-band signals, wherein the at least two sub-filter signals are generated by at least two sub-filters of the plurality of sub-filters with adjacent central frequencies.

本發明有關於聲學波信號處理與基頻信號處理領域，特別有關於一種分析濾波器組及其方法、基於分析濾波器組之即時信號處理系統及其施行方法。 The present invention relates to the field of acoustic wave signal processing and fundamental frequency signal processing, in particular to an analysis filter bank and its method, a real-time signal processing system based on the analysis filter bank and its implementation method.

一個濾波器組由多個平行的濾波器構成。該等平行濾波器分別相應多個相異頻段，其可含蓋一時域濾波器組輸入信號之全頻段或者部份頻段。該等頻段每一頻段稱為一個子帶(sub-band)，所有子帶的集合稱為子帶組。該等平行濾波器稱為子帶濾波器，濾波器組相應各子帶的輸出信號(通常亦為子帶濾波器的輸出信號)則稱為子帶信號。濾波器組之設計具有高度彈性：每個子帶的頻寬，子帶濾波器響應形狀都可獨立調整，且中心頻率相鄰之二子帶濾波器其頻率響應可部份重疊。若一濾波器組中各子帶濾波器的輸入信號皆為同一輸入信號，則稱此濾波器組為一個分析濾波器組(analysis filter bank)。 關於濾波器組之設計可參照參考文獻1至參考文獻3。 A filter bank consists of multiple parallel filters. The parallel filters correspond to a plurality of different frequency bands respectively, which can cover the whole frequency band or part of the frequency band of the input signal of a time domain filter bank. Each of these frequency bands is called a sub-band, and the set of all the sub-bands is called a sub-band group. These parallel filters are called sub-band filters, and the output signals of the corresponding sub-bands of the filter bank (usually also the output signals of the sub-band filters) are called sub-band signals. The design of the filter bank is highly flexible: the bandwidth of each sub-band and the shape of the sub-band filter response can be adjusted independently, and the frequency responses of two sub-band filters adjacent to the center frequency can partially overlap. If the input signals of the subband filters in a filter bank are all the same input signal, the filter bank is called an analysis filter bank. For the design of the filter bank, please refer to Reference 1 to Reference 3.

一般信號處理系統在應用濾波器組時，可能採用如圖1之一個習知之基於濾波器組的信號處理系統架構100。該信號處理系統架構100包括：一個分析濾波器組101，其將一時域輸入信號作濾波分頻(即作多個中心頻率相異之濾波處理以分離相異頻率之成份)以得到多個子帶信號；一個抽取器(decimator；以捨棄部份取樣點方式降低信號取樣頻率)102，其抽取該等子帶信號以得到多個相應各子帶的被抽取子帶信號；一個核心數位信號處理單元103，其針對該等被抽取信號執行指定的信號處理以得到多個相應各子帶的被修改子帶信號(即完成該信號處理的信號)；一個補零單元104，其將多個零值取樣點插入該等被修改子帶信號以將該等被修改子帶信號之取樣頻率還原至與該輸入信號相同；以及一個合成濾波器組105，其對該等還原取樣頻率之被修改子帶信號實施抗混疊(anti-aliasing)後合併為一輸出信號。基於濾波器組的信號處理系統架構適合實施基於取樣點(sample-based)的信號處理，其較利於低處理延時的設計。若該信號處理系統100為實數型輸出信號如聲學波(acoustic wave)，合成該輸出信號通常將只針對該等被修改子帶信號的實部進行。又，考量該信號處理系統100實施的算法可能需參考到相位資訊，如基頻(baseband)信號處理，或部份音頻信號算法如：移頻(frequency lowering)，相位聲碼器(phase vocoder)算法等等，需要處理複數型(即具有相位資訊)的子帶信號，故以下討論的分析濾波器組輸出之該等子帶信號均為複數型態。 When applying a filter bank in a general signal processing system, a conventional filter bank-based signal processing system architecture 100 as shown in FIG. 1 may be used. The signal processing system architecture 100 includes: an analysis filter bank 101, which filters and divides a time-domain input signal (ie, performs a plurality of filtering processes with different center frequencies to separate components of different frequencies) to obtain a plurality of subbands signal; a decimator (decimator; reducing the sampling frequency of the signal by discarding some sampling points) 102, which extracts the sub-band signals to obtain a plurality of extracted sub-band signals corresponding to each sub-band; a core digital signal processing unit 103, which performs specified signal processing on the extracted signals to obtain a plurality of modified subband signals of corresponding subbands (that is, the signal that has completed the signal processing); a zero- filling unit 104, which combines the plurality of zero values sampling points are inserted into the modified subband signals to restore the sampling frequencies of the modified subband signals to the same as the input signal; and a synthesis filter bank 105, which restores the modified subbands of the restored sampling frequencies The signals are combined into an output signal after anti-aliasing. The filter bank-based signal processing system architecture is suitable for implementing sample-based signal processing, which is more conducive to the design of low processing delay. If the signal processing system 100 is a real-type output signal such as an acoustic wave, synthesizing the output signal will typically only be performed on the real part of the modified subband signals. Also, considering that the algorithm implemented by the signal processing system 100 may need to refer to phase information, such as baseband signal processing, or some audio signal algorithms such as frequency shifting lowering), phase vocoder algorithms, etc., need to process sub-band signals of complex type (that is, with phase information), so the sub-band signals output by the analysis filter bank discussed below are all complex types. .

在即時信號處理系統的架構選取方面，除基於濾波器組的信號處理系統架構(以下簡稱為濾波器組式系統架構)外，基於分析-修改-合成框架(analysis-modification-synthesis framework,or AMS framework)實作的頻域信號處理系統架構(以下簡稱為AMS系統架構)也廣見於即時信號處理的應用。該架構其中分析運算與合成運算原則上是一對可逆運算，例如套用時-頻轉換例如短時傅利葉轉換(short-time Fourier transform,or STFT)及其逆轉換，或是離散餘弦轉換(discrete cosine transform,or DCT)及其逆轉換等。波形分析及合成運算之細節描述可參照參考文獻4、5。因頻域信號處理為基於幀的運算，其幀長的選擇直接影響頻譜之頻率解析度。若該即時信號處理系統有極低信號處理延時需求，可能就不適合用AMS系統架構實施。選取一個適當的系統架構，其方式不外乎依系統需求，將數個考慮面向排序後比較後決定。信號處理系統架構選取常見的考慮面向如：分頻(將時域波形詳細分解成不同頻率的信號成份)能力的優劣，算法延時(假設運算時間為零所得之處理延時，亦即理論上之最低處理延時)，運算量需求的高低，相位變化特性(例如是否為接近線性相 位響應)，設計彈性(例如是否造成其它設計上或參數設定的限制)，數值穩定性(是否有特殊的精確度需求，例如只適用浮點運算)等等。按一般認知而言，若考量相同的分頻能力(即可得到相同解析度的頻譜)，則用濾波器組執行分頻及波形合成，其運算量需求往往明顯高於用STFT轉換/逆轉換執行分頻及波形合成的運算量需求，但其好處則是擁有明顯較低的算法延時以及極高的設計彈性(例如可調整成任意的子帶個數，可獨立調整子帶頻寬與頻率響應形狀，同時適用於點處理或幀處理的系統設計...等等)。故尋求適用於信號處理但低運算量的濾波器組設計是濾波器組式系統架構適用於即時信號處理軟體實作或極低功率信號處理裝置的關鍵。 In terms of the architecture selection of real-time signal processing systems, in addition to the filter bank-based signal processing system architecture (hereinafter referred to as the filter bank system architecture), the analysis-modification-synthesis framework (or AMS) is based on the analysis-modification-synthesis framework (or AMS). The frequency domain signal processing system architecture (hereinafter referred to as the AMS system architecture) implemented by the framework) is also widely used in real-time signal processing applications. In this architecture, the analysis operation and the synthesis operation are in principle a pair of reversible operations, such as applying time-frequency transforms such as short-time Fourier transform (or STFT) and its inverse transform, or discrete cosine transform (discrete cosine transform) transform, or DCT) and its inverse transformation, etc. Details of waveform analysis and synthesis operations can be found in References 4 and 5. Because the frequency domain signal processing is a frame-based operation, the choice of the frame length directly affects the frequency resolution of the spectrum. If the real-time signal processing system has extremely low signal processing delay requirements, it may not be suitable for implementation with the AMS system architecture. To select an appropriate system architecture, the method is nothing more than a decision based on the system requirements, sorting and comparing several considerations. Common considerations for signal processing system architecture selection are: frequency division (decomposing the time domain waveform into signal components of different frequencies in detail), algorithm delay (the processing delay obtained by assuming that the operation time is zero, that is, the theoretical minimum processing delay), the level of computational requirements, the phase change characteristics (such as whether it is close to linear phase bit response), design flexibility (for example, whether it causes other design or parameter setting constraints), numerical stability (if there are special accuracy requirements, such as only floating-point operations) and so on. Generally speaking, if the same frequency division capability is considered (that is, the spectrum with the same resolution can be obtained), the use of filter banks to perform frequency division and waveform synthesis requires significantly higher computational requirements than using STFT conversion/inverse conversion. The computational requirements of performing frequency division and waveform synthesis, but its advantages are significantly lower algorithm delay and extremely high design flexibility (for example, it can be adjusted to any number of subbands, and the subband bandwidth and frequency can be adjusted independently. Responsive shape, while suitable for point processing or frame processing system design...etc). Therefore, seeking a filter bank design suitable for signal processing but with low computational complexity is the key for the filter bank system architecture to be suitable for real-time signal processing software implementation or very low power signal processing devices.

參考文獻references

參考文獻1：Wei, Ying, and Yong Lian. "A 16-band nonuniform FIR digital filterbank for hearing aid." 2006 IEEE Biomedical Circuits and Systems Conference. IEEE, 2006. Reference 1: Wei, Ying, and Yong Lian. "A 16-band nonuniform FIR digital filterbank for hearing aid." 2006 IEEE Biomedical Circuits and Systems Conference. IEEE, 2006.

參考文獻2：Subbulakshmi, N., and R. Manimegalai. "A survey of filter bank algorithms for biomedical applications." 2014 International Conference on Computer Communication and Informatics. IEEE, 2014. Reference 2: Subbulakshmi, N., and R. Manimegalai. "A survey of filter bank algorithms for biomedical applications." 2014 International Conference on Computer Communication and Informatics. IEEE, 2014.

參考文獻3：Necciari, Thibaud, et al. "A perceptually motivated filter bank with perfect reconstruction for audio signal processing." arXiv preprint arXiv:1601.06652 (2016). Reference 3: Necciari, Thibaud, et al. "A perceptually motivated filter bank with perfect reconstruction for audio signal processing." arXiv preprint arXiv:1601.06652 (2016).

參考文獻4：Dutoit, Thierry, and Ferran Marques. Applied Signal Processing: A MATLAB ^TM -based proof of concept. Springer Science & Business Media, 2010. Reference 4: Dutoit, Thierry, and Ferran Marques. Applied Signal Processing: A MATLAB ^TM -based proof of concept. Springer Science & Business Media, 2010.

參考文獻5：Loizou, Philipos C. Speech enhancement: theory and practice. CRC press, 2013. Reference 5: Loizou, Philipos C. Speech enhancement: theory and practice. CRC press, 2013.

鑑於上述不同系統/算法架構的相對優勢與限制，本發明之目的在於提供一種適用於即時信號處理的分析濾波器組與相應之分析濾波器組運算程序，並提出基於該分析濾波器組之二信號處理系統與相應基於該分析濾波器組運算程序之二信號處理程序。該分析濾波器組以平行之一階無限衝激響應(infinite impulse response,or IIR)濾波運算為基礎，搭配子帶響應預補償與二項式組合與旋轉器構成該分析濾波器組的子帶信號輸出。該分析濾波器組及相應之分析濾波器組運算程序兼顧低運算量，低延時與低失真。其相當適合應用於極低功率裝置之濾波器組系統實作或即時信號處理程序之實作。 In view of the relative advantages and limitations of the above-mentioned different system/algorithm architectures, the purpose of the present invention is to provide an analysis filter bank suitable for real-time signal processing and a corresponding analysis filter bank operation program, and propose a second analysis filter bank based on the analysis filter bank. A signal processing system and a corresponding signal processing program based on the analysis filter bank operation program. The analysis filter bank is based on a parallel first-order infinite impulse response (or IIR) filtering operation, with sub-band response pre-compensation and binomial combination and rotator forming the sub-bands of the analysis filter bank signal output. The analysis filter bank and the corresponding analysis filter bank operation program take into account low computational complexity, low delay and low distortion. It is quite suitable for filter bank system implementation or real-time signal processing program implementation for very low power devices.

本發明之第一態樣提供一種相應多個子帶之分析濾波器組，其將一輸入信號依該等子帶作濾波分頻以產生多個子帶信號，該等子帶為等寬，該分析濾波器組包括：一子帶響應預補償器，其將該輸入信號作一線性濾波處理以產生一響應預補償信號；中心頻率相異之多個子濾波器，其分別將該響應預補償信號作一複數型一階無限衝激響應濾波處理以產生多個子濾波信號；以及 A first aspect of the present invention provides an analysis filter bank corresponding to a plurality of sub-bands, which filters and frequency-divides an input signal according to the sub-bands to generate a plurality of sub-band signals, the sub-bands are of equal width, and the analysis The filter bank includes: a sub-band response pre-compensator, which performs a linear filtering process on the input signal to generate a response pre-compensation signal; a plurality of sub-filters with different center frequencies, which respectively make the response pre-compensation signal a complex first-order infinite impulse response filtering process to generate a plurality of sub-filtered signals; and

基於一組二項式權重之多個二項式組合與旋轉器，其每一者將至少二子濾波信號以該組二項式權重作一加權和運算，並將該加權和運算結果隨相應子帶之中心頻率旋轉一相位以產生該等子帶信號之一子帶信號，其中該至少二子濾波信號由該等子濾波器之至少二中心頻率相鄰之子濾波器產生。 A plurality of binomial combinations and rotators based on a set of binomial weights, each of which performs a weighted sum operation on at least two sub-filtered signals with the set of binomial weights, and applies the result of the weighted sum operation to the corresponding sub-filter The center frequency of the band is rotated by a phase to generate a sub-band signal of the sub-band signals, wherein the at least two sub-filtered signals are generated by at least two sub-filters of the sub-filters having adjacent center frequencies.

本發明之第二態樣提供一種兩段式分析濾波器組，其包括相應一低子帶組之一個如第一態樣之低分析濾波器組以及相應一高子帶組之一個如第一態樣之高分析濾波器組，該二分析濾波器組分別將一輸入信號作濾波分頻處理以產生子帶信號，該低分析濾波器組之該子帶響應預補償器之該線性濾波處理為一低通濾波處理，該高分析濾波器組之該子帶響應預補償器之該線性濾波處理為一高通濾波處理。 A second aspect of the present invention provides a two-stage analysis filter bank, which includes a corresponding one of a low subband group, such as the low analysis filter bank of the first aspect, and a corresponding one of a high subband group, such as the first one. A high analysis filter bank of this aspect, the two analysis filter banks respectively perform filtering and frequency division processing on an input signal to generate a subband signal, and the subband of the low analysis filter bank responds to the linear filtering process of the precompensator Being a low-pass filtering process, the linear filtering process of the sub-band response precompensator of the high analysis filter bank is a high-pass filtering process.

本發明之第三態樣提供一種三段式分析濾波器組，其包括相應一低子帶組之一個如第一態樣之低分析濾波器組，相應一中子帶組之一個如第一態樣之中分析濾波器組，以及相應一高子帶組之一個如第一態樣之高分析濾波器組，該三分析濾波器組分別將一輸入信號作濾波分頻處理以產生多個子帶信號，該低分析濾波器組之該子帶響 應預補償器之該線性濾波處理為一低通濾波處理，該中分析濾波器組之該子帶響應預補償器之該線性濾波處理為一帶通濾波處理，且該高分析濾波器組之該子帶響應預補償器之該線性濾波處理為一高通濾波處理。 A third aspect of the present invention provides a three-stage analysis filter bank, which includes one corresponding to a low subband group such as the low analysis filter bank of the first aspect, and one corresponding to a middle subband group such as the first The analysis filter bank in the aspect, and one of the corresponding high subband groups is the high analysis filter bank of the first aspect, and the three analysis filter banks respectively perform filtering and frequency division processing on an input signal to generate a plurality of subbands band signal, the subband of the low analysis filter bank The linear filtering process of the pre-compensator should be a low-pass filtering process, the linear filtering process of the sub-band response pre-compensator of the mid-analysis filter bank is a band-pass filtering process, and the high-analysis filter bank The linear filtering process of the subband response precompensator is a high-pass filtering process.

本發明之第四態樣提供一種濾波器組式系統，其包括： A fourth aspect of the present invention provides a filter bank system comprising:

一個如第一態樣之分析濾波器組，其將一輸入信號作分頻濾波處理以產生多個子帶信號； an analysis filter bank as in the first aspect, which divides and filters an input signal to generate a plurality of subband signals;

一個抽取器，其以一抽取倍率抽取該等子帶信號或其振幅以產生一輸入頻譜； a decimator that decimates the subband signals or their amplitudes at a decimation factor to generate an input spectrum;

一個核心數位信號處理單元，其將該輸入頻譜執行指定的數位信號處理以決定每一時間該等子帶信號相應之多個子帶權重；以及 a core digital signal processing unit that performs specified digital signal processing on the input spectrum to determine a plurality of subband weights corresponding to the subband signals at each time; and

一個子帶組合器，其對該等子帶信號或其之實部以相應之該等子帶權重作一加權和運算以產生一輸出信號。 A subband combiner that performs a weighted sum operation on the subband signals or their real parts with the corresponding subband weights to generate an output signal.

本發明之第五態樣提供一種混合式信號處理系統，其包括： A fifth aspect of the present invention provides a hybrid signal processing system, which includes:

一個成幀與時-頻轉換器，其將一輸入信號依時間劃分成等長且等間距之多個信號幀，並將該等信號幀分別作一時-頻轉換以產生多個帶信號； a framing and time-frequency converter, which divides an input signal into a plurality of signal frames of equal length and interval according to time, and performs a time-frequency conversion on the signal frames respectively to generate a plurality of band signals;

多個如第一態樣之分析濾波器組，其分別將該等帶信號作濾波分頻以產生多個子帶信號； a plurality of analysis filter banks according to the first aspect, which respectively filter and frequency-divide the equal-band signals to generate a plurality of sub-band signals;

一個抽取器，其以一抽取倍率抽取該等子帶信號或其振幅以產生一輸入頻譜； a decimator that decimates the subband signals or their amplitudes at a decimation factor to generate an input spectrum;

一個核心數位信號處理單元，其對該輸入頻譜執行指定的信號處理以決定該等帶信號之每一者相應之多個子帶信號之多個子帶權重； a core digital signal processing unit that performs specified signal processing on the input spectrum to determine a plurality of subband weights for a plurality of subband signals corresponding to each of the plurality of band signals;

多個子帶組合器，其每一者將該等帶信號之一帶信號相應之該等子帶信號以其相應該等子帶權重進行一加權和運算以產生多個被修改帶信號之一被修改帶信號；以及 a plurality of sub-band combiners, each of which performs a weighted sum operation on the corresponding sub-band signals of the one of the band signals with their corresponding sub-band weights to generate one of a plurality of modified band signals modified with signal; and

一個頻-時轉換器，其對該等被修改帶信號相應同一時間之多個取樣點作一頻-時轉換以產生一輸出信號。 A frequency-to-time converter that performs a frequency-to-time conversion of the modified band signals corresponding to a plurality of sampling points at the same time to generate an output signal.

本發明之第六態樣提供一種相應多個子帶之濾波器組運算程序，其包括下列步驟： A sixth aspect of the present invention provides a filter bank operation program corresponding to a plurality of subbands, which includes the following steps:

對一輸入信號之至少一取樣點進行一線性濾波運算以得到一響應預補償信號之至少一取樣點； performing a linear filtering operation on at least one sampling point of an input signal to obtain at least one sampling point corresponding to the pre-compensated signal;

將該響應預補償信號之該至少一取樣點進行中心頻率相異之多個複數型一階無限衝激響應濾波運算以得到多個子濾波信號，其每一子濾波信號包含至少一取樣點；以及 performing a plurality of complex first-order infinite impulse response filtering operations with different center frequencies on the at least one sampling point of the response pre-compensated signal to obtain a plurality of sub-filtered signals, each of which includes at least one sampling point; and

從該等子濾波信號中選擇相應該等子帶之多個子集，其每一者包含相同個數、由中心頻率相鄰之至少二濾波運算得到之至少二子濾波信號，將該等子集之每一子集相應同一時間之至少二子濾波信號取樣點以一組二項式權重進行一加權和運算，並將該加權和運算結果隨相應子帶之中心頻率旋轉一相位以得到多個子帶信號之一子帶信號，其包括至少一取樣點。 A plurality of subsets corresponding to the subbands are selected from the subfiltered signals, each of which includes the same number of at least two subfiltered signals obtained by at least two filtering operations with adjacent center frequencies, and the subsets Each of the subsets corresponds to at least two sub-filtered signal sampling points at the same time to perform a weighted sum operation with a set of binomial weights, and rotate the result of the weighted sum operation by a phase with the center frequency of the corresponding sub-band to obtain a plurality of sub-bands A subband signal of the signal, which includes at least one sample point.

本發明之第七態樣提供一種濾波器組式信號處理程序，其包括下列步驟： A seventh aspect of the present invention provides a filter bank type signal processing program, which includes the following steps:

對一輸入信號之至少一取樣點執行一個如第六態樣之濾波器組運算程序以得到多個子帶信號，其每一者包括至少一取樣點； performing a filter bank operation procedure as in the sixth aspect on at least one sampling point of an input signal to obtain a plurality of subband signals, each of which includes at least one sampling point;

若一抽取周期結束，則抽取該等子帶信號或其振幅以得到一輸入頻譜，對該輸入頻譜執行一核心信號處理程序以決定該等子帶信號相應之多個子帶權重，並開始算一個新的抽取周期；以及 If a decimation period ends, extract the sub-band signals or their amplitudes to obtain an input spectrum, execute a core signal processing procedure on the input spectrum to determine a plurality of sub-band weights corresponding to the sub-band signals, and start to calculate a a new draw cycle; and

對該等子帶信號相應同一時間之多個取樣點或其之實部以該等子帶權重進行一加權和運算以得到一輸出信號之至少一取樣點。 A weighted sum operation is performed on the sub-band signals corresponding to a plurality of sampling points at the same time or their real parts with the sub-band weights to obtain at least one sampling point of an output signal.

本發明之第八態樣提供一種混合式信號處理程序，其包括下列步驟： An eighth aspect of the present invention provides a mixed signal processing program, which includes the following steps:

對一輸入信號之至少一信號幀分別進行一時-頻轉換運算以得到多個帶信號，其每一者包括相應同一頻帶之至少一頻譜取樣點； performing a time-frequency conversion operation on at least one signal frame of an input signal to obtain a plurality of band signals, each of which includes at least one spectral sampling point corresponding to the same frequency band;

對該等帶信號分別執行一如第六態樣之濾波器組運算程序以得到多個子帶信號，其每一者包括至少一取樣點； respectively performing a filter bank operation procedure as in the sixth aspect on the band signals to obtain a plurality of subband signals, each of which includes at least one sampling point;

若一抽取周期結束，則抽取該等子帶信號或其振幅以得到一輸入頻譜，對該輸入頻譜執行一核心信號處理程序以決定該等帶信號之每一者相應之多個子帶信號之多個子帶權重，並開始算一個新的抽取周期； After a decimation period ends, the subband signals or their amplitudes are extracted to obtain an input spectrum, and a core signal processing procedure is performed on the input spectrum to determine the number of subband signals corresponding to each of the subband signals subband weights, and start to calculate a new extraction cycle;

將該等帶信號之每一者相應之該等子帶信號以其相應該等子帶權重進行一加權和運算以得到多個被修改帶信號之一被修改帶信號，其包括至少一取樣點；以及 performing a weighted sum operation on the subband signals corresponding to each of the band signals and the corresponding subband weights to obtain one modified band signal of a plurality of modified band signals, which includes at least one sampling point ;as well as

對該等被修改帶信號相應同一時間之多個取樣點進行一頻-時轉換運算以產生一輸出信號之多個取樣點。 A frequency-to-time conversion operation is performed on a plurality of sample points corresponding to the same time of the modified band signals to generate a plurality of sample points of an output signal.

100:基於濾波器組的信號處理系統架構 100: Filter Bank-Based Signal Processing System Architecture

101:分析濾波器組 101: Analysis Filter Banks

102:抽取器 102: Extractor

103:核心數位信號處理單元 103: Core digital signal processing unit

104:補零單元 104: Zero filling unit

105:合成濾波器組 105: Synthesis Filter Banks

101:分析濾波器組 101: Analysis Filter Banks

201:子帶響應預補償器 201: Subband response precompensator

202:多個一階IIR子濾波器 202: Multiple first-order IIR subfilters

203:多個二項式組合與旋轉器 203: Multiple Binomial Combinations with Spinners

700:兩段式分析濾波器組 700: Two-stage analysis filter bank

701:低分析濾波器組 701: Low Analysis Filter Bank

702:高分析濾波器組 702: High Analysis Filter Bank

703:子帶響應預補償器 703: Subband response precompensator

704:多個一階IIR子濾波器 704: Multiple first-order IIR subfilters

705:多個二項式組合與旋轉器 705: Multiple Binomial Combinations with Spinners

706:子帶響應預補償器 706: Subband response precompensator

707:多個一階IIR子濾波器 707: Multiple first-order IIR subfilters

708:多個二項式組合與旋轉器 708: Multiple Binomial Combinations with Spinners

800:三段式分析濾波器組 800: Three-stage analysis filter bank

801:低分析濾波器組 801: Low Analysis Filter Bank

802:中分析濾波器組 802: Medium Analysis Filter Bank

803:高分析濾波器組 803: High Analysis Filter Bank

804:子帶響應預補償器 804: Subband response precompensator

805:多個一階IIR子濾波器 805: Multiple first-order IIR subfilters

806:多個二項式組合與旋轉器 806: Multiple Binomial Combinations with Spinners

807:子帶響應預補償器 807: Subband response precompensator

808:多個一階IIR子濾波器 808: Multiple first-order IIR subfilters

809:多個二項式組合與旋轉器 809: Multiple Binomial Combinations with Spinners

810:子帶響應預補償器 810: Subband response precompensator

811:多個一階IIR子濾波器 811: Multiple first-order IIR subfilters

812:多個二項式組合與旋轉器 812: Multiple binomial combinations with spinners

1200:濾波器組式信號處理系統 1200: Filter Bank Signal Processing System

1201:分析濾波器組 1201: Analysis Filter Banks

1202:抽取器 1202: Extractor

1203:核心數位信號處理單元 1203: Core digital signal processing unit

1204:子帶組合器 1204: Subband Combiner

1400:混合式信號處理系統 1400: Mixed Signal Processing System

1401:成幀與時-頻轉換器 1401: Framing and Time-Frequency Converters

1402:多個分析濾波器組 1402: Multiple Analysis Filter Banks

1403:抽取器 1403: Extractor

1404:核心數位信號處理單元 1404: Core Digital Signal Processing Unit

1405:多個子帶組合器 1405: Multiple Subband Combiners

1406:頻-時轉換器 1406: Frequency-Time Converter

〔圖1〕係習知之基於濾波器組的信號處理系統架構。 [FIG. 1] is a conventional filter bank-based signal processing system architecture.

〔圖2〕係本發明之第一實施例之分析濾波器組方塊圖。 [FIG. 2] is a block diagram of an analysis filter bank according to the first embodiment of the present invention.

〔圖3〕係本發明之以不同階二項式權重加權組合子濾波器輸出所得之子帶等效濾波器頻率響應圖。 [FIG. 3] is the frequency response diagram of the sub-band equivalent filter obtained by combining the outputs of the sub-filters with different order binomial weights according to the present invention.

〔圖4〕係採一階二項式組合與旋轉器的分析濾波器組範例之響應圖。 [Fig. 4] is a response diagram of an example analysis filter bank using a first-order binomial combination and a rotator.

〔圖5〕係採二階二項式組合與旋轉器的分析濾波器組範例之響應圖。 [Fig. 5] is a response diagram of an example analysis filter bank using a second-order binomial combination and a rotator.

〔圖6〕係本發明之第二實施例之濾波器組運算程序之流程圖。 [FIG. 6] is a flow chart of the filter bank operation procedure of the second embodiment of the present invention.

〔圖7〕係本發明之第三實施例之兩段式分析濾波器組方塊圖。 [FIG. 7] is a block diagram of a two-stage analysis filter bank according to the third embodiment of the present invention.

〔圖8〕係本發明之第四實施例之三段式分析濾波器組方塊圖。 [FIG. 8] is a block diagram of a three-stage analysis filter bank according to the fourth embodiment of the present invention.

〔圖9〕係採用一階二項式組合與旋轉器之一個兩段式分析濾波器組範例之響應圖。 [Fig. 9] is a response plot of an example of a two-stage analysis filter bank using a first-order binomial combination and a rotator.

〔圖10〕係採用一階二項式組合與旋轉器之一個兩段式分析濾波器組範例之響應圖。 [Fig. 10] is a response plot of an example of a two-stage analysis filter bank using a first-order binomial combination and a rotator.

〔圖11〕係採用一階二項式組合與旋轉器之一個三段式分析濾波器組範例之響應圖。 [Fig. 11] is a response plot of an example of a three-stage analytical filter bank using a first-order binomial combination and a rotator.

〔圖12〕係本發明之第五實施例之濾波器組式系統架構圖。 [FIG. 12] is a structural diagram of a filter bank type system according to the fifth embodiment of the present invention.

〔圖13〕係本發明之第六實施例之濾波器組式信號處理程序之流程圖。 [FIG. 13] is a flow chart of the filter bank type signal processing procedure of the sixth embodiment of the present invention.

〔圖14〕係本發明之第七實施例之混合式信號處理系統方塊圖。 [FIG. 14] is a block diagram of a mixed signal processing system according to a seventh embodiment of the present invention.

〔圖15〕係本發明之第八實施例之混合式信號處理程序之流程圖。 [FIG. 15] is a flow chart of the mixed signal processing procedure of the eighth embodiment of the present invention.

為使熟習本發明所屬技術領域之一般技藝者能更進一步了解本發明，下文特列舉本發明之較佳實施例，並配合所附圖式，詳 細說明本發明的構成內容及所欲達成之功效。 In order to enable those of ordinary skill in the technical field to which the present invention pertains to further understand the present invention, preferred embodiments of the present invention are listed below, together with the accompanying drawings. The constituent content and desired effect of the present invention will be described in detail.

圖2為本發明之第一實施例之一分析濾波器組方塊圖。該分析濾波器組101相應依中心頻率由低至高編號的S個子帶。該分析濾波器組101包括K個平行之一階IIR子濾波器202、S個平行之基於一組M階二項式權重的組合器與旋轉器(以下稱為M階二項式組合與旋轉器)203、以及一個可選的子帶響應預補償器(sub-band response pre-compensator)201。此結構下每一子帶信號係由一相應的M階二項式組合與旋轉器將該等IIR濾波器之多個輸出信號(以下簡稱為子濾波信號)的子集以該組M階二項式權重作一加權和運算與一相位旋轉運算所產生的信號。其可等效於將一輸入信號通過多個獨立濾波器(以下稱為子帶等效濾波器)後所產生的信號。 FIG. 2 is a block diagram of an analysis filter bank according to the first embodiment of the present invention. The analysis filter bank 101 corresponds to S subbands numbered from low to high according to the center frequency. The analysis filter bank 101 includes K parallel first- order IIR sub-filters 202, S parallel combiners and rotators based on a set of M -order binomial weights (hereinafter referred to as M -order binomial combining and rotating 203, and an optional sub-band response pre-compensator (sub-band response pre-compensator) 201. Under this structure, each sub-band signal is composed of a corresponding M -order binomial combination and a rotator of the plurality of output signals of the IIR filters (hereinafter referred to as sub-filtered signals) subsets of the set of M -order binomial The signal generated by a weighted sum operation and a phase rotation operation on the term weights. It can be equivalent to a signal generated by passing an input signal through a plurality of independent filters (hereinafter referred to as sub-band equivalent filters).

該子帶響應預補償器201作用為改變該分析濾波器組101之該等子帶等效濾波器的頻率響應，其係將該分析濾波器組101的輸入信號作一線性濾波處理產生一響應預補償信號。該濾波器為一具少許非零固定係數的線性濾波器，以少量的運算補償該分析濾波器組隨不同組態設定(如各子帶頻寬的設定，相鄰子帶間共用子濾波信號的比例等)造成之該等子帶等效濾波器頻率響應的共同缺陷，例如止帶衰減(stopband attenuation)不足，或較明顯之通帶增益與群延時(group delay)的波動(ripples)等等。因需隨組態設定調整其係數， 故於後段介紹該分析濾波器組101的實施例時再一併說明該子帶響應預補償器201之濾波器公式。 The sub-band response pre-compensator 201 is used to change the frequency response of the sub-band equivalent filters of the analysis filter bank 101, which is to perform a linear filtering process on the input signal of the analysis filter bank 101 to generate a response pre-compensated signal. The filter is a linear filter with a few non-zero fixed coefficients, which uses a small amount of operations to compensate the analysis filter bank with different configuration settings (such as the setting of the bandwidth of each sub-band, the sharing of sub-filtered signals between adjacent sub-bands) The common defects of the frequency response of these sub-band equivalent filters, such as insufficient stopband attenuation, or obvious ripples of passband gain and group delay, etc. Wait. Because the coefficients need to be adjusted with the configuration settings, Therefore, the filter formula of the subband response precompensator 201 will be described together when the embodiment of the analysis filter bank 101 is introduced in the following paragraph.

該等平行的一階IIR子濾波器202具相異之中心頻率，且依中心頻率由低至高編號。該等IIR子濾波器202分別將該響應預補償信號作複數型一階IIR之濾波處理以產生多個子濾波信號。該濾波處理可用以下運算表示： The parallel first- order IIR sub-filters 202 have different center frequencies and are numbered from low to high center frequencies. The IIR sub-filters 202 respectively perform a complex first-order IIR filtering process on the response pre-compensated signal to generate a plurality of sub-filtered signals. This filtering process can be represented by the following operations:

註：該等IIR子濾波器202之每一者其頻寬由相應之至少一子帶頻寬決定。例如在每一子帶等寬之設計中，該等IIR子濾波器202具有相同頻寬。在子帶頻寬隨子帶中心頻率上升之設計中，該等IIR子濾波器202每一者之頻寬也隨濾波器中心頻率上升。 Note: The bandwidth of each of the IIR sub-filters 202 is determined by the corresponding at least one sub-band bandwidth. For example, in a design of equal width for each subband, the IIR subfilters 202 have the same bandwidth. In designs where the subband bandwidth increases with the subband center frequency, the bandwidth of each of the IIR subfilters 202 also increases with the filter center frequency.

該等M階(M

公式(5)隨子帶編號旋轉相位之作用在於調整該分析濾波器組101的總響應，使各子帶信號大致同調(加總時不相互抵消)，並縮小該分析濾波器組101輸出信號的延時。相鄰子帶相位差值θ原則上沒有限制，但若能從-π/2的整數倍角中選值，其使該分析濾波器組101之總響應之群延時夠低且增益響應與群延時響應波動皆不至於太嚴重，則可同時改善總響應又避免增加複數型乘法運算。本發明於以下各設計範例中均採用θ=-π/2的設定，因此相位旋轉僅需要數值之實部/虛部對調抑或變號之運算。 The function of formula (5) rotating the phase with the subband number is to adjust the overall response of the analysis filter bank 101 to make the subband signals approximately coherent (not cancel each other when summed), and to reduce the output signal of the analysis filter bank 101 delay. The phase difference value θ of adjacent subbands is not limited in principle, but if the value can be selected from an integer multiple of -π /2, it will make the group delay of the overall response of the analysis filter bank 101 low enough and the gain response and group delay The response fluctuations are not too severe, and the overall response can be improved without adding complex multiplication operations. The present invention adopts the setting of θ =- π /2 in the following design examples, so the phase rotation only needs the operation of real part/imaginary part exchange or sign change of the value.

又，以以上所述如該等IIR濾波運算，基於二項式權重之加權和運算，或相位旋轉運算等均屬於線性運算，因此該等運算可自由合併或前後對調順序，甚至移至該分析濾波器之前級/後級。圖2及相應公式(1)(5)僅表示一種可行的運算順序。 Also, as mentioned above, the IIR filtering operations, weighted sum operations based on binomial weights, or phase rotation operations are all linear operations, so these operations can be freely combined or reversed in order, or even moved to this analysis. Filter pre/post. Figure 2 and the corresponding formulas (1) and (5) only represent a possible operation sequence.

以下討論組合與旋轉器共用子濾波信號的方式。若該等M階二項式組合與旋轉器203之任兩編號相鄰者共用P個子濾波信號(P=0即每一子濾波信號只被一組合與旋轉器使用，不被多個組合與旋轉器共用)，則k _s 可表示為： The manner in which the sub-filtered signal is combined and shared with the rotator is discussed below. If these M -order binomial combinations and any two adjacent numbers of the rotator 203 share P sub-filtered signals ( P = 0, that is, each sub-filter signal is only used by one combination and rotator, not used by multiple combinations and rotators). Rotator shared), then k _s can be expressed as:

採用高階二項式組合與旋轉器(M

接下來討論相應等寬子帶的分析濾波器組設計。因其子帶等寬，該分析濾波器組101的每一IIR子濾波器具相等頻寬設定，且濾波器中心頻率在頻率軸上等距分佈。該分析濾波器組101產生的效果是：該等子帶等效濾波器響應(包含增益與群延時響應)在通帶附近的形狀彼此高度相似，且該分析濾波器組101總響應隨頻率呈現週 期波動。為提高該等子帶等效濾波器響應與該分析濾波器組101總響應之平坦度，該子帶響應預補償器之該線性濾波運算為： Next, the design of the analysis filter bank for the corresponding equal-width subbands is discussed. Since the sub-bands are of equal width, each IIR sub-filter of the analysis filter bank 101 has equal bandwidth settings, and the filter center frequencies are equally spaced on the frequency axis. The effect produced by the analysis filter bank 101 is that the sub-band equivalent filter responses (including the gain and group delay responses) are highly similar in shape to each other near the passband, and the overall response of the analysis filter bank 101 appears with frequency week period fluctuations. In order to improve the flatness of the subband equivalent filter responses and the overall response of the analysis filter bank 101, the linear filtering operation of the subband response precompensator is:

圖4顯示採用一階二項式組合與旋轉器之一分析濾波器組設計範例之響應(圖中實線為其子帶等效濾波器響應，虛線為該分析濾波器組的總響應，點線為提高其高頻側子帶信號權值得到的總響應)。該分析濾波器組輸入信號的取樣頻率是12kHz，從零頻(DC)至Nyquist頻率(取樣頻率的一半，亦為該數位音訊之最高頻率)切分成18個等寬子帶，故每個子帶頻寬為333Hz。該分析濾波器組101需19個一階IIR子濾波器，每一子帶信號由二個子濾波信號組成，且該 二同頻寬且同中心頻率之IIR子濾波器的中心頻率位於該子帶與相鄰二子帶交界。 Figure 4 shows the response of an analytical filterbank design example using a first-order binomial combination and a rotator (the solid line in the figure is the subband equivalent filter response, the dashed line is the overall response of the analytical filterbank, the dots line is the total response obtained by increasing the weight of the subband signal on its high frequency side). The sampling frequency of the input signal of the analysis filter bank is 12kHz, which is divided into 18 equal-width subbands from zero frequency (DC) to the Nyquist frequency (half the sampling frequency, which is also the highest frequency of the digital audio), so each subband The bandwidth is 333Hz. The analysis filter bank 101 requires 19 first-order IIR sub-filters, each sub-band signal consists of two sub-filtered signals, and the The center frequency of the two IIR sub-filters with the same bandwidth and the same center frequency is located at the boundary between the sub-band and the adjacent two sub-bands.

圖5顯示採用二階二項式組合與旋轉器之一分析濾波器組設計範例之響應(圖中實線為其子帶等效濾波器響應，虛線為該分析濾波器組的總響應，點線為提高其高頻側子帶信號權值得到的總響應)。該分析濾波器組輸入信號的取樣頻率與子帶定義(子帶個數，子帶頻率範圍/頻寬)都與上例相同。該分析濾波器組需37個一階IIR子濾波器，每一子帶信號由三個子濾波信號組成，其中二個IIR子濾波器的中心頻率位於該子帶與相鄰二子帶交界，另一IIR子濾波器的中心頻率位於該子帶中心。為使圖示清晰，此二範例採較少子帶之濾波器組設定。實際應用之濾波器組子帶個數將更多。 Figure 5 shows the response of an analytical filterbank design example using a second-order binomial combination and a rotator (the solid line is the subband equivalent filter response, the dashed line is the overall response of the analytical filterbank, the dotted line total response to increase the weight of its high-frequency side subband signal). The sampling frequency and sub-band definition (number of sub-bands, frequency range/bandwidth of sub-bands) of the input signal of the analysis filter bank are the same as in the previous example. The analysis filter bank requires 37 first-order IIR sub-filters, and each sub-band signal is composed of three sub-filtered signals. The center frequency of the IIR subfilter is at the center of this subband. For clarity of illustration, these two examples use filter bank settings with fewer subbands. The number of filter bank subbands in practical application will be more.

從圖示可見，此二範例中採二階二項式組合與旋轉器的分析濾波器組之該等子帶等效濾波器，其增益響應過渡帶較採一階二項式組合與旋轉器的分析濾波器組的版本更陡峭，其響應通帶則略寬/平坦。但得到該較佳響應特性的代價是複數乘法數量提升約兩倍，濾波器群延時也提升約兩倍。另外，不論採一或二階二項式組合與旋轉器的範例，該二分析濾波器組的總響應(包含增益響應與群延時響應)皆大致平坦，保有接近線性相位的特性(註)。該二分析濾波器組所有子帶衝激響應的加總(即整體衝激響應)是幾乎無線性失真的衝 激函數，即是說在不提供額外增益於各子帶信號的前提下，子帶信號的加總像是延遲一小段時間的輸入波形。但採越高階二項式組合之濾波器組系統響應對子帶權值的調整越敏感，總響應(包含增益與群延時)之波動也越明顯。 As can be seen from the figure, the subband equivalent filters of the analysis filter bank using the second-order binomial combination and the rotator in these two examples have a gain response transition band compared with the first-order binomial combination and the rotator. The version of the analysis filter bank is steeper and has a slightly wider/flater response passband. However, the cost of obtaining this better response characteristic is about twice the number of complex multiplications and about twice the filter group delay. In addition, regardless of the first- or second-order binomial combination and rotator example, the overall response (including gain response and group delay response) of the two-analytical filter bank is generally flat, maintaining a near-linear phase characteristic (Note). The sum of the impulse responses of all subbands of the two-analysis filter bank (ie, the overall impulse response) is an impulse with almost no linear distortion. Exciter function, that is, without providing additional gain to each sub-band signal, the sum of the sub-band signals is like the input waveform delayed for a small period of time. However, the higher-order binomial combination filter bank system response is more sensitive to the adjustment of subband weights, and the fluctuation of the total response (including gain and group delay) is also more obvious.

註：但個別子帶等效濾波器頻率響應並非平坦，其不具線性相位特性，其群延時亦可能高於該分析濾波器組之總響應的群延時。 Note: However, the frequency response of the equivalent filter of individual subbands is not flat, it does not have linear phase characteristics, and its group delay may also be higher than the group delay of the total response of the analysis filter bank.

實務上採用一或二階二項式組合與旋轉器的分析濾波器組，其子帶等效濾波器已可得到良好的止帶衰減與過渡帶衰減斜率。採越高階二項式組合與旋轉器的優點是：讓子帶等效濾波器得到越高的止帶衰減量與過渡帶衰減斜率(每增加一階，大約可多獲得20dB至30dB止帶衰減)，並且使子帶等效濾波器有較為平坦的通帶響應。但代價是：1)該等子濾波信號被多個組合器共用的比例下降，整體運算量也隨二項式組合與旋轉器的階數上升，2)該等子帶等效濾波器與該分析濾波器組總響應之群延時也隨組合器的階數增加，以及3)信號處理算法對子帶的加權將使該總響應產生更明顯的群延時響應波動。因此除非對止帶衰減需求極高，建議優先採用一或二階二項式組合與旋轉器來設計該分析濾波器組。 In practice, the analysis filter bank of first or second order binomial combination and rotator is used, and its sub-band equivalent filter can already obtain good stop-band attenuation and transition-band attenuation slope. The advantage of using a higher-order binomial combination and rotator is that the sub-band equivalent filter can obtain a higher stop-band attenuation and transition-band attenuation slope (each increase of one order, about 20dB to 30dB more stopband attenuation can be obtained ), and make the subband equivalent filter have a relatively flat passband response. But the cost is: 1) the ratio of these sub-filtered signals shared by multiple combiners decreases, and the overall computation amount also increases with the binomial combination and the order of the rotator; 2) these sub-band equivalent filters are the same as the The group delay of the overall response of the analysis filter bank also increases with the order of the combiner, and 3) the weighting of the subbands by the signal processing algorithm will result in more pronounced group delay response fluctuations in the overall response. Therefore, unless the need for stopband attenuation is extremely high, it is recommended to use first or second order binomial combinations and rotators in preference to designing this analysis filter bank.

該分析濾波器組101可調整為相應非等寬子帶的組態，其常應用於音訊處理。簡言之，人耳聽覺有濾波分頻的結構，一般稱其 為聽覺濾波器。正常之聽覺濾波器對越高頻信號其相應的濾波處理有越寬頻的表現，而對較低頻信號其相應的濾波處理頻寬約略維持不變。該濾波頻寬通常被稱為臨界帶(critical band)寬。因此，文獻中音訊處理系統之濾波器組常被設計成近似於聽覺濾波器之組態，即在低頻(如500Hz或以下)配置等頻寬之窄頻子帶濾波器，越高頻處則配置越寬頻寬之子帶濾波器。前述濾波器組設計公式(1)~(6)於非等寬子帶的組態下仍適用。在設計時需要注意的是： The analysis filter bank 101 can be adjusted to the configuration of corresponding unequal width subbands, which are commonly used in audio processing. In short, human hearing has a structure of filtering and frequency division, which is generally called for the auditory filter. The normal auditory filter has a wider frequency performance for the higher frequency signal, while the corresponding filter bandwidth of the lower frequency signal remains roughly unchanged. This filtering bandwidth is often referred to as the critical band width. Therefore, the filter bank of the audio processing system in the literature is often designed to be similar to the configuration of the auditory filter, that is, a narrow-band sub-band filter with equal bandwidth is arranged at low frequencies (such as 500 Hz or below), and the higher the frequency, the higher the frequency. Configure the subband filter with wider bandwidth. The aforementioned filter bank design formulas (1) to (6) are still applicable in the configuration of unequal width subbands. Things to keep in mind when designing:

-在等寬子帶的組態中，該等IIR子濾波器202可設計為具相等頻寬且其中心頻率在頻率軸上等距分佈，如此濾波公式可化簡(因b _k 值皆相等，可移出濾波器公式(1)~如該輸入信號先乘上b _k 再進入該分析濾波器組101)。但採用相應非等寬子帶的分析濾波器組時不能依相同方式化簡。 - In the configuration of equal-width sub-bands, the IIR sub-filters 202 can be designed to have equal bandwidths and their center frequencies are equally spaced on the frequency axis, so that the filtering formula can be simplified (because the values of b and _k are all equal) , can be removed from the filter formula (1) ~ if the input signal is first multiplied by b _k before entering the analysis filter bank 101). However, it cannot be simplified in the same way when using an analysis filter bank of corresponding unequal width subbands.

-在不等寬子帶的組態中，該子帶響應預補償器201不能有效補償響應，此時可停止該子帶響應預補償器201作用(例如令C _CMP =0，或以輸入信號作為該等IIR子濾波器202輸入)並改由提高該等IIR子濾波器頻寬以壓低該分析濾波器組101之總響應(包含增益響應與群延時響應)的波動，其代價是小幅增加該等子帶等效濾波器頻率響應之過渡帶寬度。 - In the configuration of unequal width sub-bands, the sub-band response pre-compensator 201 cannot effectively compensate the response, at this time, the function of the sub-band response pre-compensator 201 can be stopped (for example, set C _CMP =0, or use the input signal as the IIR sub-filters 202 input) and instead increase the IIR sub-filter bandwidth to suppress fluctuations in the overall response (including gain response and group delay response) of the analysis filter bank 101, at the cost of a small increase The transition band width of the frequency responses of the subband equivalent filters.

除以一實體裝置實施外，該分析濾波器組101之功能亦可 用執行於至少一處理器之一等效程序實施。圖6為本發明之第二實施例之一濾波器組運算程序之流程圖。該濾波器組運算程序相應多個子帶，其依中心頻率由低至高編號。該等流程步驟著重在對於一連續輸入音訊之一片段的處理方法，此因在即時音訊處理應用中，各步驟均將信號作分段運算處理；後面步驟可採用前面步驟運算得到之一輸出信號片段作為輸入並隨即進行運算，無需等待前步驟得到完整輸出信號。以下在說明該濾波器組運算程序之流程步驟時參考公式(1)~(7)及其相應說明文字。 In addition to being implemented in a physical device, the function of the analysis filter bank 101 can also be Implemented with an equivalent program executing on at least one processor. FIG. 6 is a flow chart of a filter bank operation procedure according to the second embodiment of the present invention. The filter bank operation procedure corresponds to a plurality of subbands, which are numbered from low to high according to the center frequency. These flow steps focus on the processing method for a segment of a continuous input audio. Therefore, in real-time audio processing applications, each step performs a segmental operation on the signal; the latter steps can use the previous steps to obtain an output signal. Fragments are taken as input and computed immediately, without waiting for the full output signal from previous steps. The following formulas (1) to (7) and their corresponding descriptions are referred to when describing the flow steps of the filter bank operation procedure.

在圖6中，對一輸入信號之至少一取樣點進行一線性濾波運算以得到一響應預補償信號之至少一取樣點(步驟S101)。參考段落[0017]及[0024]之說明，該線性濾波運算相應公式(7)之運算，其作用在於使子帶等效濾波器之頻率響應更平坦，並抵消總響應之增益與群延時波動。 In FIG. 6, a linear filtering operation is performed on at least one sampling point of an input signal to obtain at least one sampling point corresponding to the pre-compensated signal (step S101). Referring to the descriptions of paragraphs [0017] and [0024], the linear filtering operation corresponds to the operation of formula (7), and its function is to make the frequency response of the sub-band equivalent filter flatter, and to offset the gain and group delay fluctuations of the total response .

對該響應預補償信號之該至少一取樣點進行中心頻率相異之多個複數型一階IIR濾波運算以得到多個子濾波信號(步驟S102)。參考段落[0018]之說明，該等複數型一階IIR濾波運算相應公式(1)~(3)之運算。該等子濾波信號其每一者包括之至少一取樣點。 A plurality of complex first-order IIR filtering operations with different center frequencies are performed on the at least one sampling point of the response pre-compensated signal to obtain a plurality of sub-filtered signals (step S102). Referring to the description in paragraph [0018], these complex first-order IIR filtering operations correspond to the operations of formulas (1) to (3). Each of the sub-filtered signals includes at least one sample point.

從該等子濾波信號中選擇相應該等子帶之多個子集，其每一者包含相同個數、由中心頻率相鄰之至少二濾波運算得到之至少二 子濾波信號，將該等子集之每一子集相應同一時間之至少二個子濾波信號取樣點以一組二項式權重進行一加權和運算，並將該加權和運算結果隨相應子帶之中心頻率旋轉一相位以得到多個子帶信號之一子帶信號(步驟S103)，其包括至少一取樣點。參考段落[0019]之說明，該二項式權重相應公式(4)，該加權和運算以及該旋轉運算相應公式(5)之運算。參考段落[0020]之說明，相鄰子帶相位差值θ採用-π/2的整數倍角，因此對相應兩頻率相鄰子帶之二子濾波信號子集在進行該旋轉運算時，其相應之該二旋轉相位差異為-π/2弧之整數倍。另外參考段落[0022]之說明，編號相鄰之二組合與旋轉器可共用子濾波信號，因此相應兩頻率相鄰子帶之二子濾波信號子集有相同之子濾波信號。 A plurality of subsets corresponding to the subbands are selected from the subfiltered signals, each of which includes the same number of at least two subfiltered signals obtained by at least two filtering operations with adjacent center frequencies, and the subsets Each of the subsets corresponds to at least two sub-filtered signal sampling points at the same time to perform a weighted sum operation with a set of binomial weights, and rotate the result of the weighted sum operation by a phase with the center frequency of the corresponding subband to obtain a plurality of subbands. A sub-band signal of the band signal (step S103), which includes at least one sampling point. Referring to the description of paragraph [0019], the binomial weight corresponds to the formula (4), the weighted sum operation and the rotation operation correspond to the operation of the formula (5). With reference to the description of paragraph [0020], the adjacent subband phase difference value θ adopts an integer multiple of -π /2, so when the rotation operation is performed for the two sub-filtered signal subsets of the adjacent sub-bands of the corresponding two frequencies, the corresponding The difference between the two rotational phases is an integer multiple of -π /2 arcs. In addition, referring to the description in paragraph [0022], two adjacent combinations and rotators can share sub-filtered signals, so the two sub-filtered signal subsets corresponding to two adjacent frequency subbands have the same sub-filtered signals.

該分析濾波器組101調整為相應非等寬子帶之組態時有一個弱點：在音訊處理應用中，高頻子帶通常較低頻子帶頻寬相對寬很多。若搭配較低階二項式組合與旋轉器，該分析濾波器組101之中心頻率較高的子帶等效濾波器可能有過渡帶太寬/止帶抑制不足(如低於40dB)等問題，如此可能影響部份信號處理算法的表現。 The analysis filter bank 101 has a weakness in the configuration of the corresponding unequal width subbands: in audio processing applications, the high frequency subbands are usually much wider than the lower frequency subbands. If combined with a lower-order binomial combination and a rotator, the sub-band equivalent filter with a higher center frequency of the analysis filter bank 101 may have problems such as too wide transition band/insufficient stopband suppression (eg, lower than 40dB). , which may affect the performance of some signal processing algorithms.

為解決此問題，本發明之第三實施例提出一個兩段式分析濾波器組700，其由平行之二個前述之分析濾波器組組合而成，圖7為其方塊圖。該二分析濾波器組為一個低分析濾波器組701與一個高 分析濾波器組702。與該二分析濾波器組701、702分別相應的一低子帶組與一高子帶組，其含蓋頻段範圍以一交界頻率f _BND 分隔。該低子帶組有S _L 個子帶，其中心頻率皆低於f _BND 。該高子帶組有S _H 個子帶，其中心頻率皆不低於f _BND (註)。該二子帶組之每一者均可分別設定為非等寬，等寬，或部份等寬的子帶組。該二分析濾波器組701、702分別將一輸入信號作濾波分頻處理以產生多個子帶信號。 To solve this problem, a third embodiment of the present invention proposes a two-stage analysis filter bank 700, which is formed by combining two parallel analysis filter banks, as shown in FIG. 7 . The two analysis filter banks are a low analysis filter bank 701 and a high analysis filter bank 702 . A low sub-band group and a high sub-band group corresponding to the two analysis filter groups 701 and 702 respectively, and their covered frequency bands are separated by a boundary frequency f _BND . The low sub-band group has SL _sub -bands whose center frequencies are all lower than f _BND . The high sub-band group has SH _sub -bands whose center frequencies are not lower than f _BND (Note). Each of the two subband groups can be respectively set as non-equal-width, equal-width, or partially equal-width subband groups. The two analysis filter banks 701 and 702 respectively perform filtering and frequency division processing on an input signal to generate a plurality of subband signals.

註：設定該交界頻率f _BND 應使該高子帶組包含頻寬過寬使子帶等效濾波器響應低頻側之止帶抑制能力不足的高頻子帶，以及預期因補償聽損可能被大幅提升子帶信號增益的中至高頻子帶 Note: The boundary frequency f _BND should be set so that the high sub-band group contains the high-frequency sub-band whose bandwidth is too wide to make the sub-band equivalent filter respond to the low-frequency side of the stop-band suppression ability, and it is expected that the compensation for hearing loss may be affected by the high frequency sub-band. Mid-to-high frequency subbands with substantially increased subband signal gain

為使該兩段式分析濾波器組700的總響應(包含增益與群延時響應)在該交界頻率處平滑無斷點，加入以下設計限制： To make the overall response of the two-stage analysis filter bank 700 (including gain and group delay responses) smooth without breakpoints at the crossover frequency, the following design constraints are added:

-該二分析濾波器組701、702之每一者之該等組合器皆為M階二項式組合與旋轉器，且任兩編號相鄰之二組合器共用P個子濾波信號。 - the combiners of each of the two analysis filter banks 701, 702 are M -order binomial combiners and rotators, and any two adjacent combiners with numbers share P sub-filtered signals.

-該二子帶響應預補償器703、706之二頻率響應於各頻率之相位差為π/2的整數倍之固定值(欲達成此效果，該二子帶響應預補償器可採用具相同群延時線性相位濾波器)。如此可自由設定該交界頻率f _BND ，且不增加該等組合器705、708的相位旋轉運算量。 - The phase difference of the two subband response precompensators 703 and 706 in response to each frequency is a fixed value that is an integer multiple of π /2 (to achieve this effect, the two subband response precompensators can use the same group delay linear phase filter). In this way, the boundary frequency f _BND can be freely set without increasing the phase rotation computation amount of the combiners 705 and 708 .

-該低分析濾波器組701的最高中心頻率IIR子濾波器與該高分析濾波器組702的最低中心頻率IIR子濾波器具相同中心頻率與頻寬，亦即： - the highest center frequency IIR sub-filter of the low analysis filter bank 701 and the lowest center frequency IIR sub filter of the high analysis filter bank 702 have the same center frequency and bandwidth, that is:

在該低分析濾波器組701中，該子帶響應預補償器703之該線性濾波運算為一低通濾波運算以增加該低分析濾波器組701之各子帶等效濾波器的帶外高頻抑制，該低通濾波運算可表示為： In the low analysis filter bank 701 , the linear filtering operation of the subband response precompensator 703 is a low pass filtering operation to increase the out-of-band height of each subband equivalent filter of the low analysis filter bank 701 frequency suppression, the low-pass filtering operation can be expressed as:

在該高分析濾波器組702中，該子帶響應預補償器706之該線性濾波運算為一高通濾波運算以增加該高分析濾波器組702之各子帶等效濾波器的帶外低頻抑制。該高通濾波運算可表示為： In the high analysis filter bank 702 , the linear filtering operation of the subband response precompensator 706 is a high pass filtering operation to increase the out-of-band low frequency rejection of the subband equivalent filters of the high analysis filter bank 702 . The high-pass filtering operation can be expressed as:

除以一實體裝置實施外，該兩段式分析濾波器組700之功能亦可用執行於至少一處理器之一兩段式濾波器組運算程序實施。該兩段式濾波器組運算程序對一輸入信號之至少一取樣點分別執行相應二子帶組之二濾波器組運算程序以得到多個子帶信號。該二子帶組之定義參考段落[0035]之說明。該二濾波器組運算程序參考段落[0030]~[0033]之說明，並搭配該兩段式分析濾波器組之設定與計算公式(參考段落[0036]~[0038]之說明)。該等子帶信號之每一者包括至少一取樣點。 In addition to being implemented by a physical device, the functions of the two-stage analysis filter bank 700 can also be implemented by a two-stage filter bank operation program executed on at least one processor. The two-stage filter bank operation program respectively executes two filter bank operation procedures of corresponding two subband groups on at least one sampling point of an input signal to obtain a plurality of subband signals. For the definition of the two subband groups, refer to the description in paragraph [0035]. Refer to the descriptions of paragraphs [0030]~[0033] for the operation procedure of the two-stage filter bank, and match the setting and calculation formula of the two-stage analysis filter bank (refer to the descriptions of paragraphs [0036]~[0038]). Each of the subband signals includes at least one sample point.

在上述兩段式分析濾波器組700設計中，該二分析濾波器組701、702均只加強各子帶等效濾波器之單側之止帶抑制能力。若考量子帶數量較少，各子帶普遍擁有較寬頻寬的狀況，則相應中段頻率的子帶等效濾波器其頻率響應高/低頻兩側止帶仍可能同時面臨抑制量不足的問題。故本發明之第四實施例提出一個三段式分析濾波器組800，其由平行之三個前述之分析濾波器組組合而成。 In the above-mentioned design of the two-stage analysis filter bank 700 , the two analysis filter banks 701 and 702 only strengthen the stopband suppression capability of one side of each subband equivalent filter. If the number of sub-bands to be considered is small and each sub-band generally has a wider bandwidth, the sub-band equivalent filter of the corresponding mid-band frequency may still face the problem of insufficient suppression in the stop-bands on both sides of the high/low frequency response of the corresponding mid-band frequency. Therefore, the fourth embodiment of the present invention provides a three-stage analysis filter bank 800, which is composed of three parallel analysis filter banks.

圖8為該三分析濾波器組之方塊圖，其包括一個低分析濾 波器組801、一個中分析濾波器組802、及一個高分析濾波器組803。與該三分析濾波器組分別相應的一低子帶組、一中子帶組、與一高子帶組，其含蓋頻段範圍以一低交界頻率f _BNDL 及一高交界頻率f _BNDH 分隔。該低子帶組有S _L 個子帶，其中心頻率皆低於該低交界頻率f _BNDL ，該中子帶組有S _M 個子帶，其中心頻率皆介於該低交界頻率f _BNDL 至該高交界頻率f _BNDH 間，該高子帶組有S _H 個子帶，其中心頻率皆高於該高交界頻率f _BNDH 。該三子帶組之每一者均可設定為非等寬、等寬、或部份等寬的子帶組。該三分析濾波器組801、802、803分別將一輸入信號作濾波分頻處理以產生多個子帶信號。 FIG. 8 is a block diagram of the three analysis filter banks, which include a low analysis filter bank 801 , a medium analysis filter bank 802 , and a high analysis filter bank 803 . A low subband group, a neutron subband group, and a high subband group corresponding to the three analysis filter groups respectively, and their covered frequency bands are separated by a low boundary frequency f _BNDL and a high boundary frequency f _BNDH . The low subband group has SL _subbands whose center frequencies are all lower than the low boundary frequency f _BNDL , and the neutron subband group has SM _subbands whose center frequencies are all between the low boundary frequency f _BNDL to the high Between the junction frequencies f _BNDH , the high sub-band group has SH sub-bands, and the center frequencies of which _are all higher than the high junction frequency f _BNDH . Each of the three subband groups can be configured as a non-equal width, equal width, or partial equal width subband group. The three analysis filter banks 801 , 802 and 803 respectively perform filtering and frequency division processing on an input signal to generate a plurality of subband signals.

為使該三段式分析濾波器組800之總響應(包含增益與群延時響應)在該二交界頻率處平滑無斷點，加入以下設計限制： In order to make the overall response of the three-stage analysis filter bank 800 (including gain and group delay response) smooth without breakpoints at the two boundary frequencies, the following design constraints are added:

-該三分析濾波器組801、802、803之每一者之該等組合器皆為M階二項式組合與旋轉器，且任兩編號相鄰之二組合器共用P個子濾波信號。 - The combiners of each of the three analysis filter banks 801, 802, 803 are M -order binomial combiners and rotators, and any two adjacent combiners with numbers share P sub-filtered signals.

-該二子帶響應預補償器804、807之二頻率響應於各頻率之相位差異為π/2的整數倍之固定值，且該二子帶響應預補償器807、810之二頻率響應於各頻率之相位差異也為π/2的整數倍之固定值(欲達成此效果，該三子帶響應預補償器可採用具相同群延時線性相位濾波器)。如此則可自由設定該二交界頻率f _BNDL 與 f _BNDH ，且不增加該等組合器806、809、812的相位旋轉運算量。 - The two sub-band response pre-compensators 804, 807 have a fixed value whose phase difference is an integer multiple of π /2 in response to each frequency, and the two sub-band response pre-compensators 807, 810 are in a frequency response to each frequency The phase difference is also a fixed value of an integer multiple of π /2 (to achieve this effect, the three-subband response precompensator can use a linear phase filter with the same group delay). In this way, the two boundary frequencies f _BNDL and f _BNDH can be freely set without increasing the phase rotation computation amount of the combiners 806 , 809 and 812 .

-該低分析濾波器組801中的最高中心頻率IIR子濾波器與該中分析濾波器組802中的最低中心頻率IIR子濾波器具相同中心頻率與頻寬，且該中分析濾波器組802中的最高中心頻率IIR子濾波器與高分析濾波器組803中的最低中心頻率IIR子濾波器具相同中心頻率與頻寬，亦即： - the highest center frequency IIR subfilter in the low analysis filter bank 801 and the lowest center frequency IIR subfilter in the middle analysis filter bank 802 have the same center frequency and bandwidth, and the middle analysis filter bank 802 has the same center frequency and bandwidth The highest center frequency IIR sub-filter of and the lowest center frequency IIR sub-filter in the high analysis filter bank 803 have the same center frequency and bandwidth, that is:

該低分析濾波器組801的子帶響應預補償器之該線性濾波運算為一低通濾波運算以增加該低分析濾波器組801之各子帶等效濾波器的帶外高頻抑制。該中分析濾波器組802的子帶響應預補償 器之該線性濾波運算為一帶通濾波運算以同時增加該中分析濾波器組802之各子帶等效濾波器的帶外低頻與高頻抑制。該高分析濾波器組803的子帶響應預補償器之該線性濾波運算為一高通濾波運算以增加該高分析濾波器組803之各子帶等效濾波器的帶外低頻抑制。該三子帶響應預補償器之濾波運算可分別表示為： The linear filtering operation of the subband response precompensator of the low analysis filter bank 801 is a low pass filtering operation to increase the out-of-band high frequency rejection of the subband equivalent filters of the low analysis filter bank 801 . The sub-band response pre-compensation of the analysis filter bank 802 The linear filtering operation of the filter is a bandpass filtering operation to simultaneously increase the out-of-band low frequency and high frequency rejection of each sub-band equivalent filter of the mid-analysis filter bank 802 . The linear filtering operation of the subband response precompensator of the high analysis filter bank 803 is a high pass filtering operation to increase the out-of-band low frequency rejection of the subband equivalent filters of the high analysis filter bank 803 . The filtering operations of the three-subband response precompensator can be expressed as:

在該低分析濾波器組801中，為搭配公式(17)該子帶響應預補償器804之運算，該等IIR子濾波器805的b _k 設定改為： In the low analysis filter bank 801, in order to match the operation of the subband response precompensator 804 in equation (17), the b _k settings of the IIR subfilters 805 are changed to:

在該中分析濾波器組802中，為搭配公式(18)該子帶響應預補償器807之運算，該等IIR子濾波器808的b _k 設定改為： In the middle analysis filter bank 802, in order to match the operation of the subband response precompensator 807 in formula (18), the b _k settings of the IIR subfilters 808 are changed to:

在該高分析濾波器組803中，為搭配公式(19)該子帶響應預補償器810之運算，該等IIR子濾波器811的b _k 設定改為： In the high analysis filter bank 803, in order to match the operation of the subband response precompensator 810 in formula (19), the b _k settings of the IIR subfilters 811 are changed to:

φ _H,s =-π+θ‧(S _L +S _M +s) (25) φ _{H , s} =- π + θ ‧( S _L + S _M + s ) (25)

注意在該二段式分析濾波器組700及該三段式分析濾波器組800設計中，該等IIR子濾波器之前饋係數並非如同公式(3)之僅依IIR子濾波器頻寬決定，而是改成同時隨IIR子濾波器頻寬及IIR子濾波器中心頻率變化。因此即便其中任一分析濾波器組改採用等寬子帶，該等IIR子濾波器運算之前饋項在計算上亦不能如前設計般共 用前饋項化簡。 Note that in the design of the two-stage analysis filter bank 700 and the three-stage analysis filter bank 800, the feedforward coefficients of the IIR sub-filters are not determined only by the bandwidth of the IIR sub-filters as in formula (3). Instead, it is changed to change with the bandwidth of the IIR sub-filter and the center frequency of the IIR sub-filter at the same time. Therefore, even if one of the analysis filter banks is changed to use equal-width subbands, the feedforward terms of the IIR subfilters cannot be calculated in the same way as the previous design. Simplify with a feedforward term.

除以一實體裝置實施外，該三段式分析濾波器組800之功能亦可用執行於至少一處理器之一三段式濾波器組運算程序實施。該三段式濾波器組運算程序對一輸入信號之至少一取樣點分別執行相應三子帶組之三濾波器組運算程序以得到多個子帶信號。該三子帶組之定義參考段落[0041]之說明。該三濾波器組運算程序參考段落[0030]~[0033]之說明，並搭配該三段式分析濾波器組之設定與計算公式(參考段落[0042]~[0047]之說明)。該等子帶信號之每一者包括至少一取樣點。 In addition to being implemented by a physical device, the functions of the three-stage analysis filter bank 800 can also be implemented by a three-stage filter bank operation program executed in at least one processor. The three-stage filter bank operation program respectively executes the three filter bank operation procedures of the corresponding three sub-band groups on at least one sampling point of an input signal to obtain a plurality of sub-band signals. The definition of the three-subband group refers to the description of paragraph [0041]. Refer to the descriptions of paragraphs [0030]~[0033] for the operation procedure of the three-stage filter bank, and match the setting and calculation formulas of the three-stage analysis filter bank (refer to the descriptions of paragraphs [0042]~[0047]). Each of the subband signals includes at least one sample point.

圖9為採用非等寬子帶之一兩段式分析濾波器組設計範例(圖中實線為其子帶等效濾波器響應，虛線為該兩段式分析濾波器組的總響應)，其採用上述兩段式分析濾波器組設計，並使用一階二項式組合與旋轉器。該分析濾波器組輸入信號的取樣頻率設為12kHz。該分析濾波器組高頻側兩倍頻間切分7個子帶，低頻側為等寬子帶(低於1kHz有3個等寬子帶)，如此DC至Nyquist頻率總共分成17個子帶。值得注意的是，此系統整體衝激響應失真狀況明顯可見，與前述等寬子帶的分析濾波器組接近理想的整體衝激響應完全不同。此因為子帶頻寬的差異大，造成各子帶群延時的差異大所導致。 Figure 9 is a design example of a two-stage analysis filter bank using a subband of unequal width (the solid line in the figure is the sub-band equivalent filter response, and the dotted line is the total response of the two-stage analysis filter bank), It adopts the two-stage analytical filter bank design described above, and uses a first-order binomial combination and rotator. The sampling frequency of the input signal to the analysis filter bank is set to 12kHz. The high-frequency side of the analysis filter bank is divided into 7 sub-bands between double frequencies, and the low-frequency side is equal-width sub-bands (3 equal-width sub-bands below 1 kHz), so the DC to Nyquist frequencies are divided into 17 sub-bands in total. It is worth noting that the overall impulse response distortion of this system is clearly visible, which is completely different from the nearly ideal overall impulse response of the aforementioned equal-width subband analysis filter bank. This is caused by the large difference in subband bandwidths, resulting in large differences in the group delays of each subband.

圖10同為一兩段式分析濾波器組之設計範例，其與圖9 範例高頻側同為兩倍頻間切分7個子帶，而1kHz以下有6個等寬子帶。低頻側頻率解析度將近加倍，但子帶總數(23個)僅較圖9範例增加6個。因此，設計者可針對應用的需求，在維持頻譜或聲譜(spectrogram，即頻譜對時間的作圖)低頻部份的頻率解析度的前提下，利用非等寬子帶之配置有效降低分析濾波器組所需子帶個數。 Figure 10 is also a design example of a two-stage analysis filter bank, which is similar to that of Figure 9 The high-frequency side of the example is also divided into 7 subbands between double frequencies, and there are 6 equal-width subbands below 1kHz. The frequency resolution on the low-frequency side is nearly doubled, but the total number of subbands (23) is only 6 more than the example in Figure 9. Therefore, according to the requirements of the application, the designer can effectively reduce the analysis filtering by using the configuration of the unequal width sub-bands on the premise of maintaining the frequency resolution of the low-frequency part of the spectrum or the spectrogram (that is, the plot of the spectrum versus time). The number of subbands required by the device group.

圖11為一三段式分析濾波器組設計範例，其與圖10範例之非等寬子帶配置方式相同。該例之三段式分析濾波器組中的子帶預補償器對相應中頻子帶至高頻子帶之子帶等效濾波器提供更佳的止帶衰減，但僅微幅增加運算量與總響應群延時(約增加一個取樣時間，0.083ms)。 FIG. 11 is a design example of a three-stage analysis filter bank, which is configured in the same manner as the non-equal-width subbands in the example of FIG. 10 . The sub-band pre-compensator in the three-stage analysis filter bank of this example provides better stop-band attenuation for the sub-band equivalent filter from the corresponding intermediate frequency sub-band to the high-frequency sub-band, but only slightly increases the computational complexity and Total response group delay (approximately add one sample time, 0.083ms).

圖12為本發明之第五實施例之濾波器組式系統架構圖。該濾波器組式信號處理系統1200包括一個分析濾波器組1201、一個抽取器1202、一個核心數位信號處理單元1203、以及一個子帶組合器1204。該分析濾波器組1201將一輸入信號(註)依相應之多個子帶作分頻濾波處理以產生多個子帶信號。該分析濾波器組1201的實施方式可採用前述之該分析濾波器組(參考段落[0016]~[0024]之說明)、該二段式分析濾波器組(參考段落[0035]~[0038]之說明)、或者該三段式分析濾波器組(參考段落[0041]~[0046]之說明)。 FIG. 12 is a structural diagram of a filter bank system according to a fifth embodiment of the present invention. The filter bank signal processing system 1200 includes an analysis filter bank 1201 , a decimator 1202 , a core digital signal processing unit 1203 , and a subband combiner 1204 . The analysis filter bank 1201 performs frequency division filtering processing on an input signal (Note) according to a plurality of corresponding sub-bands to generate a plurality of sub-band signals. The implementation of the analysis filter bank 1201 can adopt the aforementioned analysis filter bank (refer to the description of paragraphs [0016]~[0024]), the two-stage analysis filter bank (refer to paragraphs [0035]~[0038]) description), or the three-stage analysis filter bank (refer to the description of paragraphs [0041]~[0046]).

註：在聲學應用中，該輸入信號通常為一數位化之波形，其可能來自 一個類比-數位轉換器輸出或來自一個信號儲存裝置，或者再經降取樣器降低取樣頻率至僅保留聆聽者之可聽頻率範圍後輸入該濾波器組式信號處理系統1200。降取樣可避免運算浪費在處理聽者感知不到的高頻聲。此外也可避免聽者感知不到的高頻聲的波形佔用有限的數值運算動態範圍。在基頻信號處理應用中，該輸入信號可能來自一個類比-數位轉換器輸出，或者再經降取樣處理再輸入以保留帶內信號(in-band signal)，排除帶外信號，並優化數值運算動態範圍。 Note: In acoustic applications, the input signal is usually a digitized waveform, which may come from An analog-to-digital converter output is either from a signal storage device, or is input to the filter bank signal processing system 1200 after downsampling the sampling frequency to preserve only the audible frequency range of the listener. Downsampling avoids wasting computation on high-frequency sounds that are not perceived by the listener. In addition, it can also be avoided that the waveform of high-frequency sound that is not perceived by the listener occupies a limited dynamic range of numerical operations. In fundamental-band signal processing applications, the input signal may come from an analog-to-digital converter output, or be downsampled and input to preserve the in-band signal, exclude out-of-band signals, and optimize numerical operations Dynamic Range.

該抽取器1202以一倍率N抽取該等子帶信號，即每隔一抽取週期之時間(N個子帶信號取樣時間)將相應同一時間之該等子帶信號依頻率排列以產生多個輸入頻譜之一輸入頻譜。設y _FB,s 為該分析濾波器組之編號s子帶信號，則該輸入頻譜可表示為：Y _h ={y _FB,1[hN],y _FB,2[hN],..y _FB,S [hN]}，其中h為該輸入頻譜的時間足標。若該核心數位信號處理單元1203不使用相位資訊，則可僅抽取該等子帶信號之振幅(絕對值)，即將相應同一時間之該等子帶信號之振幅依頻率排列產生多個輸入頻譜之一輸入頻譜，其可表示為：Y _h ={|y _FB,1[hN]|,|y _FB,2[hN]|,..|y _FB,S [hN]|}。又，為滿足Nyquist定理，並降低該抽取處理後頻譜中被折疊成份的能量，經該抽取處理後輸入頻譜之幀率f _SAM /N須高於最寬子帶頻寬。 The decimator 1202 decimates the sub-band signals at a rate N , that is, the sub-band signals corresponding to the same time are arranged in frequency at every one decimation period ( N sub-band signal sampling times) to generate a plurality of input spectrums One of the input spectrum. Let y _{FB , s} be the number s subband signal of the analysis filter bank, then the input spectrum can be expressed as: Y _h ={ y _{FB ,1} [ hN ], y _{FB ,2} [ hN ],.. y _{FB , S} [ hN ]}, where h is the time scale of the input spectrum. If the core digital signal processing unit 1203 does not use phase information, it can only extract the amplitudes (absolute values) of the sub-band signals, that is, the amplitudes of the sub-band signals corresponding to the same time are arranged in frequency to generate a plurality of input spectrums An input spectrum, which can be expressed as: Y _h ={| y _{FB ,1} [ hN ]|,| y _{FB ,2} [ hN ]|,..| y _{FB , S} [ hN ]|}. Furthermore, in order to satisfy Nyquist's theorem and reduce the energy of the folded components in the spectrum after the decimation process, the frame rate f _SAM / N of the input spectrum after the decimation process must be higher than the widest subband bandwidth.

該核心數位信號處理單元1203對該等輸入頻譜之每一者 執行指定之數位信號處理以決定每一時間該等子帶相應之多個子帶權重。該指定之數位信號處理可能包括多種類型之頻域信號處理，例如基頻信號處理或聲學處理之等化(equalization)，或者聲學處理之動態範圍壓縮(dynamic range compression)、降噪(noise reduction)、去殘響(dereverberation)、音源分離(source separation)、回授抑制或嘯音抑制(feedback reduction or howling reduction)...等。上述每一種信號處理功能皆可等效於將一頻譜之各頻率成份以一權重調整其強度或相位以得到一輸出之頻譜。該多種信號處理之合併功能亦等效於將該輸入頻譜之每一者各頻率成份以一權重調整其強度或相位以得到相應之一修改頻譜。因此可計算每一子帶中心頻率附近之該修改頻譜譜值與該輸入頻譜譜值之比值，以其決定相應子帶一之子帶權重。 The core digital signal processing unit 1203 for each of the input spectrums The specified digital signal processing is performed to determine a plurality of subband weights corresponding to the subbands at each time. The specified digital signal processing may include various types of frequency domain signal processing, such as fundamental frequency signal processing or equalization of acoustic processing, or dynamic range compression and noise reduction of acoustic processing. , dereverberation, source separation, feedback reduction or howling reduction...etc. Each of the above signal processing functions can be equivalent to adjusting the intensity or phase of each frequency component of a spectrum with a weight to obtain an output spectrum. The combining function of the multiple signal processing is also equivalent to adjusting the intensity or phase of each frequency component of the input spectrum with a weight to obtain a corresponding modified spectrum. Therefore, the ratio of the modified spectral value near the center frequency of each subband to the input spectral value can be calculated to determine the subband weight of the corresponding subband one.

該子帶組合器1204將該等子帶信號以相應之該等子帶權重作一加權和運算以產生一輸出信號，該運算可表示為： The subband combiner 1204 performs a weighted sum operation on the subband signals with the corresponding subband weights to generate an output signal, and the operation can be expressed as:

在聲學應用中，系統輸入信號與輸出信號皆為實數型態。若核心信號處理單元1203提供的各子帶相應權重也為實數型態(不含相位資訊)，則運算可化簡為分別將該等子帶信號取出實部，乘上核心信號處理單元1203提供的相應權重後加總： In acoustic applications, the input and output signals of the system are both real numbers. If the corresponding weights of the sub-bands provided by the core signal processing unit 1203 are also of the real number type (without phase information), the operation can be simplified as taking out the real parts of the sub-band signals respectively, and multiplying the signals provided by the core signal processing unit 1203 The corresponding weights are summed up:

除以一實體裝置實施外，該濾波器組式信號處理系統1200之功能亦可用執行於至少一處理器之一等效程序實施。圖13為本發明之第六實施例之濾波器組式信號處理程序之流程圖。因在即時信號處理應用需儘量縮短處理延時，該流程步驟將一連續輸入信號作重覆之分段處理；前面步驟得到之一輸出信號片段隨即供後面步驟進行運算，無需等待前面步驟得到完整輸出信號。以下在說明該濾波器組式信號處理程序之流程步驟時一併參考段落[0052]~[0055]之說明 文字。 In addition to being implemented by a physical device, the functions of the filter bank signal processing system 1200 can also be implemented by an equivalent program executing on at least one processor. FIG. 13 is a flowchart of a filter bank type signal processing procedure according to the sixth embodiment of the present invention. Because the processing delay needs to be shortened as much as possible in real-time signal processing applications, this process step processes a continuous input signal in repeated segments; an output signal segment obtained in the previous step is immediately used for the subsequent steps for operation, without waiting for the previous step to obtain a complete output. Signal. The following paragraphs [0052] to [0055] are also referred to when describing the flow steps of the filter bank type signal processing program. Word.

在圖13中，準備一輸入信號之至少一取樣點(步驟S200)。 In FIG. 13, at least one sampling point of an input signal is prepared (step S200).

對該輸入信號之該至少一取樣點執行一濾波器組運算程序以得到多個子帶信號(步驟S201)。該濾波器組運算程序的實施方式可採用前述之該濾波器組運算程序(參考段落[0030]~[0033]之說明)、該二段式濾波器組運算程序(參考段落[0039]之說明)、或者該三段式濾波器組運算程序(參考段落[0048]之說明)。該等子帶信號之每一者包括至少一取樣點。 A filter bank operation procedure is performed on the at least one sampling point of the input signal to obtain a plurality of subband signals (step S201 ). The implementation of the filter bank operation program can use the aforementioned filter bank operation program (refer to the description of paragraphs [0030]~[0033]), the two-stage filter bank operation program (refer to the description of paragraph [0039]) ), or the three-stage filter bank operation program (refer to the description of paragraph [0048]). Each of the subband signals includes at least one sample point.

檢查一抽取周期是否結束(步驟S202)。若結束則開始算一個新的抽取周期，並從步驟S203繼續執行，否則從步驟S205繼續執行。 It is checked whether a decimation period has ended (step S202). If it ends, start to count a new extraction cycle, and continue to execute from step S203; otherwise, continue to execute from step S205.

抽取該等子帶信號或其振幅以得到一輸入頻譜(步驟S203)。參考段落[0053]之說明，此即將相應同一時間之該等子帶信號或其振幅排列成為該輸入頻譜。 The subband signals or their amplitudes are extracted to obtain an input spectrum (step S203). Referring to the description in paragraph [0053], this means arranging the subband signals or their amplitudes corresponding to the same time into the input spectrum.

對該輸入頻譜執行一核心信號處理程序以決定該等子帶相應之多個子帶權重(步驟S204)。參考段落[0054]之說明，該核心信號處理程序相應第五實施例之該核心信號處理單元1203之功能，其將該輸入頻譜通過指定之頻域信號處理得到一修改頻譜。因此可計算每一子帶中心頻率附近之該修改頻譜譜值與該輸入頻譜譜值之比值， 以其決定該子帶相應之子帶權重。 Execute a core signal processing procedure on the input spectrum to determine a plurality of subband weights corresponding to the subbands (step S204). Referring to the description in paragraph [0054], the core signal processing program corresponds to the function of the core signal processing unit 1203 of the fifth embodiment, which obtains a modified spectrum by processing the input spectrum through a specified frequency domain signal. Therefore, the ratio of the modified spectral spectral value to the input spectral spectral value near the center frequency of each subband can be calculated, It determines the corresponding sub-band weight of the sub-band.

對該等子帶信號相應同一時間之多個取樣點或其之實部以該等子帶權重進行一加權和運算以得到一輸出信號之至少一取樣點(步驟S205)。其後，回到步驟S200。參考段落[0055]之說明，該加權和運算採用相應公式(27)之運算。若該輸出信號為實數型態，則該加權和運算可化簡為相應公式(29)之運算。若該核心信號處理程序決定之該等子帶權重為實數型態，則該加權和運算可採用相應公式(28)之運算。 A weighted sum operation is performed on the sub-band signals corresponding to a plurality of sampling points at the same time or their real parts with the sub-band weights to obtain at least one sampling point of an output signal (step S205 ). Then, it returns to step S200. Referring to the description of paragraph [0055], the weighted sum operation adopts the operation of the corresponding formula (27). If the output signal is of real type, the weighted sum operation can be simplified to the operation of the corresponding formula (29). If the sub-band weights determined by the core signal processing program are in the form of real numbers, the weighted sum operation can use the operation of the corresponding formula (28).

因採用階數最低IIR濾波器，子帶間共用濾波器，並搭配無需複數乘法之相位旋轉，本發明提出之分析濾波器組之運算量需求相較於其它種類分析濾波器組之運算需求為低。以相應總共S個子帶的濾波器組系統為例，若該分析濾波器組採用一階二項式組合與旋轉器，則輸出信號每一取樣點對應僅需S+1個複數型乘法於該IIR子濾波器運算之反饋項，1至S+1個實數型乘法於該IIR子濾波器運算之前饋項，一實數型乘法於該子帶響應預補償器，及S個實數型乘法於該子帶組合器(以上排除核心數位信號處理單元的運算需求)，也就是說該濾波器組式系統架構平均一個子帶僅需一個複數型乘法及一至二個實數型乘法。但若設定的子帶個數多或是該二項式階數提高，該濾波器組式系統架構的運算量仍將明顯高於以快速傅利葉轉換/逆 轉換實施的AMS系統架構，故仍有改善空間。 Because the IIR filter with the lowest order is adopted, the filter is shared among subbands, and the phase rotation without complex multiplication is used, the computational requirement of the analysis filter bank proposed by the present invention is compared with that of other types of analysis filter banks. Low. Taking the filter bank system corresponding to a total of S subbands as an example, if the analysis filter bank adopts a first-order binomial combination and rotator, then each sampling point of the output signal only needs S + 1 complex multiplications in the Feedback term of the IIR subfilter operation, 1 to S +1 real multiplications in the feedforward term of the IIR subfilter operation, one real multiplication in the subband response precompensator, and S real multiplications in the Subband combiner (the above excludes the operation requirement of the core digital signal processing unit), that is to say, the filter bank system architecture only needs one complex multiplication and one to two real multiplications per subband. However, if the number of sub-bands set is large or the order of the binomial is increased, the calculation amount of the filter bank system architecture will still be significantly higher than that of the AMS system architecture implemented by fast Fourier transform/inverse transform, so there are still room for improvement.

圖14為本發明之第七實施例之混合式信號處理系統方塊圖。該混合式信號處理系統1400包括一個成幀與時-頻轉換器1401、多個分析濾波器組1402、一個抽取器1403、一個核心數位信號處理單元1404、多個子帶組合器1405、以及一個頻-時轉換器1406。相較於第五實施例之該濾波器組式信號處理系統1200，該混合式音訊處理系統1400搭配時頻轉換以再降低運算需求。以下說明該混合式音訊處理系統1400各部件實施方法。 FIG. 14 is a block diagram of a mixed signal processing system according to a seventh embodiment of the present invention. The hybrid signal processing system 1400 includes a framing and time- frequency converter 1401, analysis filter banks 1402, a decimator 1403, a core digital signal processing unit 1404, a plurality of subband combiners 1405, and a frequency - Time converter 1406. Compared with the filter bank type signal processing system 1200 of the fifth embodiment, the hybrid audio processing system 1400 is equipped with time-frequency conversion to further reduce computing requirements. The following describes the implementation method of each component of the hybrid audio processing system 1400 .

該成幀與時-頻轉換器1401將一輸入信號依時間劃分成幀長為R個取樣點，幀間距為N個取樣點之多個信號幀(N

該等分析濾波器組1402分別將編號0至R-1帶信號作濾波分頻以產生多個子帶信號，其中每一分析濾波器組相應一帶信號所在之一頻帶再分切之多個子帶。該等分析濾波器組1402之每一者的實施方式可採用前述之該分析濾波器組(參考段落[0016]~[0024]之說明)、該二段式分析濾波器組(參考段落[0035]~[0038]之說明)、或者該三段式分析濾波器組(參考段落[0041]~[0046]之說明)。若輸入為實數型態(如聲學波)，則該等分析濾波器組1402僅需將相應單側頻譜之編號0至R/2帶信號作濾波分頻以產生多個子帶信號。該抽取器1403以一倍率M抽取該等子帶信號或其振幅以產生多個輸入頻譜之一輸入頻譜。經抽取後該等輸入頻譜之幀率降為f _SAM /(MN)，其必須仍高於該等子帶之最寬子帶之頻寬以滿足Nyquist定理。 The analysis filter banks 1402 respectively filter and frequency-divide the band signals numbered 0 to R-1 to generate a plurality of sub-band signals, wherein each analysis filter bank corresponds to a plurality of sub-bands sub-segmented in a frequency band where the band signal is located. The implementation of each of the analysis filter banks 1402 may employ the analysis filter bank described above (refer to the description of paragraphs [0016] to [0024]), the two-stage analysis filter bank (refer to paragraph [0035]) ]~[0038]), or the three-stage analysis filter bank (refer to the description of paragraphs [0041]~[0046]). If the input is a real number type (eg, acoustic wave), the analysis filter banks 1402 only need to filter and divide the signals in the numbered 0 to R/2 bands of the corresponding single-sided spectrum to generate a plurality of sub-band signals. The decimator 1403 decimates the subband signals or their amplitudes by a factor M to generate one input spectrum of a plurality of input spectrums. After decimation, the frame rate of the input spectra is reduced to f _SAM /( MN ), which must still be higher than the bandwidth of the widest subband of the subbands to satisfy Nyquist's theorem.

該核心數位信號處理單元1404對該等輸入頻譜之每一者執行指定的頻域信號處理以決定該等帶信號之每一者相應之多個子帶信號之多個子帶權重(此功能同第五實施例之核心數位信號處理 單元1203)。 The core digital signal processing unit 1404 performs specified frequency domain signal processing on each of the input spectrums to determine subband weights of the subband signals corresponding to each of the band signals (this function is the same as the fifth Core digital signal processing of an embodiment unit 1203).

該等子帶組合器1405之每一者將該等帶信號之一帶信號相應之該等子帶信號以其相應該等子帶權重作一加權和運算以產生多個被修改帶信號之一被修改帶信號。此運算可表示為： Each of the subband combiners 1405 performs a weighted sum operation on the subband signals corresponding to one of the band signals of the subband signals with their corresponding subband weights to generate one of a plurality of modified band signals Modify the band signal. This operation can be expressed as:

最後，該頻-時轉換器1406提取每一時間之該等被修改帶信號之R個取樣點作一R點之頻-時轉換(其為該R點之短時傅利葉轉換之一種逆轉換方法)以產生一輸出信號。若該輸出信號為實數型態如聲學波，則以該等被修改帶信號之共軛複數作為頻譜對稱側之多個被修改帶信號，其可表示為： Finally, the frequency- time converter 1406 extracts the R sample points of the modified band signal at each time to perform a frequency-time conversion at point R (which is an inverse conversion method of the short-time Fourier transform at point R ). ) to generate an output signal. If the output signal is in the form of a real number such as an acoustic wave, then the complex conjugates of the modified band signals are used as a plurality of modified band signals on the symmetrical side of the spectrum, which can be expressed as:

此系統實施例藉由時-頻轉換降低各分析濾波器組之取樣頻率，如此在子帶總數相同之狀況下，其各子帶的運算量可大幅降低。然而此系統之信號處理延時為該等分析濾波器組群延時加上該時-頻轉換/逆轉換的延時(其約為一幀的時間長度)。提升時-頻轉換之幀長與幀間距代價仍是提升延時，故該幀長選擇仍有賴設計者在系統層面對運算量與信號處理延時之取捨(選恰當的幀長，使系統運算量降至接近以短時傅利葉轉換/逆轉換實施的AMS系統架構，但改善信號處理延時至可接受程度)。 In this embodiment of the system, the sampling frequency of each analysis filter bank is reduced by time-frequency conversion, so that under the condition that the total number of subbands is the same, the computation amount of each subband can be greatly reduced. However, the signal processing delay of this system is the analysis filter bank delay plus the delay of the time-frequency conversion/inverse conversion (which is about the length of one frame). The cost of increasing the frame length and frame spacing of time-frequency conversion is still increasing the delay, so the choice of the frame length still depends on the designer's trade-off between the amount of computation and the delay of signal processing at the system level (selecting an appropriate frame length will increase the amount of system computation. down to AMS system architectures implemented with short-time Fourier transform/inverse transform, but with improved signal processing latency to an acceptable level).

本發明提出之基於該分析濾波器組之系統架構已知的應用限制與建議處理方式如下： The known application limitations and suggested processing methods of the system architecture based on the analysis filter bank proposed by the present invention are as follows:

-該分析濾波器組其各子帶等效濾波器之頻率響應彼此高度重疊。 考量相鄰二組合器共用子濾波信號為固定數量(P)的狀況，若採用越低階二項式組合與旋轉器設計該分析濾波器組，則其頻率響應的重疊度越高。若考量固定階數項式組合器設計時，則是P值越大其頻率響應的重疊度越高。頻率響應的重疊度高時，系統在實施如圖形等化器(graphic equalizer，即可任意指定多處頻率相應增益值之等化器)時可能產生響應誤差。以採用一階二項式組合與旋轉器設計該分析濾波器組為例，若於子帶組合時移除單一子帶信號，其造成相應頻率的頻譜衰減量將低於10dB。故若系統中的信號處理算法欲執行陷波(notching)運算，亦即希望對特定頻點附近提供高量的衰減，則需同時降低多個相鄰子帶的增益才有足夠效果。 - The frequency responses of the sub-band equivalent filters of the analysis filter bank are highly overlapping each other. Considering the situation that the number of sub-filtered signals shared by adjacent two combiners is a fixed number ( P ), if the lower-order binomial combination and rotator are used to design the analysis filter bank, the overlap of its frequency responses will be higher. When considering the design of the fixed-order term combiner, the larger the P value, the higher the overlap of the frequency response. When the overlap of the frequency responses is high, a response error may occur when the system implements a graphic equalizer (ie, an equalizer that can arbitrarily specify multiple frequency-corresponding gain values). Taking the first-order binomial combination and rotator to design the analysis filter bank as an example, if a single subband signal is removed during subband combination, the spectral attenuation of the corresponding frequency will be lower than 10dB. Therefore, if the signal processing algorithm in the system wants to perform a notching operation, that is, it wants to provide a high amount of attenuation near a specific frequency point, it is necessary to reduce the gain of multiple adjacent subbands at the same time to have sufficient effect.

-該分析濾波器組中各子帶等效濾波器的頻率選擇性限制(頻率範圍不算窄的過渡帶與衰減量有限的止帶)。再加上各子帶等效濾波器響應普遍具有非線性相位，系統在實施如圖形等化器功能時可能產生響應誤差。考慮信號處理算法對某些子帶的信號增益設定遠大於其鄰近子帶的信號增益(例如超過20dB)時，分析濾波器組的總響應在該等高增益子帶鄰近之子帶可能與預期增益不同。故若有大幅調高增益之需求，如寬動態範圍壓縮之類的信號處理算法在提高子帶權重時，建議應以漸近方式調整子帶權 重，即降低相鄰近子帶的權重差距，並可視需求增加分析濾波器組子帶的個數~例如補償較嚴重高頻聽損時，可增加高頻子帶的個數以降低鄰近子帶的權重差距。 - Limitation of frequency selectivity of the equivalent filters of each subband in the analysis filter bank (transition bands where the frequency range is not narrow and stopbands with limited attenuation). In addition, the response of the equivalent filter of each subband generally has a nonlinear phase, and the system may produce response errors when implementing functions such as graphic equalizers. Considering that the signal gain of the signal processing algorithm for some subbands is much larger than that of the adjacent subbands (for example, more than 20dB), the overall response of the analysis filter bank may be different from the expected gain in the adjacent subbands of these high gain subbands. different. Therefore, if there is a need to greatly increase the gain, it is recommended that the subband weight should be adjusted asymptotically when the signal processing algorithm such as wide dynamic range compression increases the subband weight. Heavy, that is, reduce the weight difference between adjacent sub-bands, and increase the number of sub-bands of the analysis filter group as needed. For example, when compensating for severe high-frequency hearing loss, the number of high-frequency sub-bands can be increased to reduce the number of adjacent sub-bands. weight gap.

-因前述之濾波器組式系統架構中缺乏合成濾波器組，不存在如圖1之該合成濾波器組提供的抗混疊功能，該核心數位信號處理單元於調整其提供各子帶權重時，需調慢權重隨時間變化的速度。 -Due to the lack of a synthesis filter bank in the aforementioned filter bank system architecture, there is no anti-aliasing function provided by the synthesis filter bank as shown in FIG. , it is necessary to slow down the speed of weight change over time.

除以一實體裝置實施外，該混合式信號處理系統1400之功能亦可用執行於至少一處理器之一等效程序實施。圖15為本發明之第八實施例之混合式信號處理程序之流程圖。以下在說明該混合式信號處理程序之流程步驟時一併參考段落[0065]~[0069]之說明文字。 In addition to being implemented by a physical device, the functions of the mixed- signal processing system 1400 can also be implemented by an equivalent program executing on at least one processor. FIG. 15 is a flowchart of a mixed signal processing procedure according to an eighth embodiment of the present invention. When describing the flow steps of the mixed-signal processing program below, reference is made to the description texts in paragraphs [0065] to [0069].

在圖15中，準備一輸入音訊之至少一音訊幀(步驟S300)。 In FIG. 15, at least one audio frame of an input audio is prepared (step S300).

對該輸入音訊之該至少一音訊幀分別進行一時-頻轉換運算以得到多個帶信號(步驟S301)。該時-頻轉換運算採用相應公式(30)之運算，其可參考段落[0065]之說明。該等帶信號之每一者包括相應同一頻帶之至少一頻譜取樣點。 A time-frequency conversion operation is performed on the at least one audio frame of the input audio to obtain a plurality of band signals (step S301 ). The time-frequency conversion operation adopts the operation of the corresponding formula (30), which can refer to the description of paragraph [0065]. Each of the band signals includes at least one spectral sample point corresponding to the same frequency band.

對該等帶信號分別執行一濾波器組運算程序以得到多個子帶信號(步驟S302)。參考段落[0066]之說明，該濾波器組運算程序 相應一帶信號所在之一頻帶再分切之多個子帶。該濾波器組運算程序的實施方式可採用前述之該濾波器組運算程序(參考段落[0030]~[0033]之說明)、該二段式濾波器組運算程序(參考段落[0039]之說明)、或者該三段式濾波器組運算程序(參考段落[0048]之說明)。該等子帶信號之每一者包括至少一取樣點。 A filter bank operation procedure is respectively performed on the equal-band signals to obtain a plurality of sub-band signals (step S302). Referring to the description of paragraph [0066], the filter bank operation program A plurality of sub-bands sub-segmented in a frequency band corresponding to a band of signals. The implementation of the filter bank operation program can use the aforementioned filter bank operation program (refer to the description of paragraphs [0030]~[0033]), the two-stage filter bank operation program (refer to the description of paragraph [0039]) ), or the three-stage filter bank operation program (refer to the description of paragraph [0048]). Each of the subband signals includes at least one sample point.

檢查檢查一抽取周期是否結束(步驟S303)。若結束則開始算一個新的抽取周期，並從步驟S304繼續執行，否則從步驟S306繼續執行。 It is checked to see if a decimation period has ended (step S303). If it ends, start to count a new extraction cycle, and continue to execute from step S304; otherwise, continue to execute from step S306.

抽取該等子帶信號或其振幅以得到一輸入頻譜(步驟S304)。如第六實施例之步驟S203，此步驟即將相應同一時間之該等子帶信號或其振幅依頻率排列成為該輸入頻譜。 The subband signals or their amplitudes are extracted to obtain an input spectrum (step S304). As in step S203 of the sixth embodiment, this step is to arrange the subband signals or their amplitudes corresponding to the same time according to frequency into the input spectrum.

對該輸入頻譜執行一核心信號處理程序以決定該等帶信號之每一者相應之多個子帶信號之多個子帶權重(步驟S305)。此程序功能同於第六實施例之該核心信號處理程序。 A core signal processing procedure is performed on the input spectrum to determine a plurality of subband weights of a plurality of subband signals corresponding to each of the band signals (step S305). The function of this program is the same as that of the core signal processing program of the sixth embodiment.

將該等帶信號之每一者相應之該等子帶信號以其相應該等子帶權重進行一加權和運算以得到多個被修改帶信號之一被修改帶信號(步驟S306)，其包括至少一取樣點。該加權和運算採用相應公式(31)之運算。 Performing a weighted sum operation on the subband signals corresponding to each of the band signals and the corresponding subband weights to obtain one modified band signal of a plurality of modified band signals (step S306 ), which includes at least one sampling point. The weighted sum operation adopts the operation of the corresponding formula (31).

對該等被修改帶信號相應同一時間之多個取樣點進行一 頻-時轉換運算以得到一輸出信號之多個取樣點(步驟S307)。其後，回到步驟S300。該頻-時轉換運算採用相應公式(32)~(35)之運算，並參考段落[0069]之說明。 A multiple sampling point corresponding to the same time of the modified band signals is subjected to a A frequency-time conversion operation is performed to obtain a plurality of sampling points of an output signal (step S307). Then, it returns to step S300. The frequency-time conversion operation adopts the operation of the corresponding formulas (32) to (35), and refer to the description of paragraph [0069].

雖然本發明已參照較佳具體例及舉例性附圖敘述如上，惟其應不被視為係限制性者。熟悉本技藝者對其形態及具體例之內容做各種修改、省略及變化，均不離開本發明之請求項之所主張範圍。 While the present invention has been described above with reference to preferred embodiments and illustrative drawings, it should not be construed as limiting. Those skilled in the art can make various modifications, omissions and changes to the form and the content of the specific examples, all without departing from the claimed scope of the claims of the present invention.

101:分析濾波器組 101: Analysis Filter Banks

201:子帶響應預補償器 201: Subband response precompensator

202:多個一階無限衝激響應(IIR)子濾波器 202: Multiple first-order infinite impulse response (IIR) subfilters

203:多個二項式組合與旋轉器 203: Multiple Binomial Combinations with Spinners

一種相應多個子帶之分析濾波器組，其將一輸入信號依該等子帶作濾波分頻以產生多個子帶信號，該等子帶為等寬，該分析濾波器組包括：一子帶響應預補償器，其將該輸入信號作一線性濾波處理以產生一響應預補償信號；中心頻率相異之多個子濾波器，其分別將該響應預補償信號作一複數型一階無限衝激響應濾波處理以產生多個子濾波信號；以及基於一組二項式權重之多個二項式組合與旋轉器，其每一者將至少二子濾波信號以該組二項式權重作一加權和運算，並將該加權和運算結果隨相應子帶之中心頻率旋轉一相位以產生該等子帶信號之一子帶信號，其中該至少二子濾波信號由該等子濾波器之至少二中心頻率相鄰之子濾波器產生。 An analysis filter bank corresponding to a plurality of sub-bands, which filters and frequency-divides an input signal according to the sub-bands to generate a plurality of sub-band signals, the sub-bands are of equal width, and the analysis filter bank comprises: a sub-band A response pre-compensator, which performs a linear filtering process on the input signal to generate a response pre-compensation signal; a plurality of sub-filters with different center frequencies, which respectively process the response pre-compensation signal into a complex first-order infinite impulse responsive to the filtering process to generate a plurality of sub-filtered signals; and a plurality of binomial combinations and rotators based on a set of binomial weights, each of which performs a weighted sum operation on at least two sub-filtered signals with the set of binomial weights , and rotate the result of the weighted sum operation by a phase with the center frequency of the corresponding sub-band to generate a sub-band signal of the sub-band signals, wherein the at least two sub-filtered signals are adjacent by at least two center frequencies of the sub-filters The child filter is generated. 如請求項1之分析濾波器組，其中相應兩頻率相鄰子帶之二組合與旋轉器共用該等子濾波信號之至少一子濾波信號。 The analysis filter bank of claim 1, wherein two combinations of corresponding two frequency adjacent subbands share at least one subfiltered signal of the subfiltered signals with the rotator. 如請求項2之分析濾波器組，其中相應兩頻率相鄰子帶之二組合與旋轉器之二旋轉相位差異為-π/2弧之整數倍。 The analysis filter bank of claim 2, wherein the phase difference between two combinations of adjacent subbands corresponding to two frequencies and two rotations of the rotator is an integer multiple of -π/2 arcs. 如請求項3之分析濾波器組，其中該子帶響應預補償器之該線性濾波運算為該輸入信號與該輸入信號之一延時版本之一 加權和運算。 The analysis filter bank of claim 3, wherein the linear filtering operation of the subband response precompensator is one of the input signal and a delayed version of the input signal Weighted sum operation. 一種包括二個如請求項1之分析濾波器組之兩段式分析濾波器組，該二分析濾波器組為一相應一低子帶組之低分析濾波器組以及一相應一高子帶組之高分析濾波器組，該二分析濾波器組分別將一輸入信號作濾波分頻處理以產生多個子帶信號，該低分析濾波器組之該子帶響應預補償器之該線性濾波處理為一低通濾波處理，該高分析濾波器組之該子帶響應預補償器之該線性濾波運算為一高通濾波運算。 A two-stage analysis filter bank comprising two analysis filter banks as claimed in item 1, the two analysis filter banks being a low analysis filter bank corresponding to a low subband group and a corresponding high subband group The high analysis filter bank, the two analysis filter banks respectively filter and divide an input signal to generate a plurality of subband signals, and the linear filtering processing of the subband response precompensator of the low analysis filter bank is as follows A low-pass filtering process, the linear filtering operation of the sub-band response precompensator of the high analysis filter bank is a high-pass filtering operation. 如請求項5之兩段式分析濾波器組，其中該二分析濾波器組之每一者之該等組合與旋轉器基於同一組二項式權重，且相應任兩相鄰子帶之二組合與旋轉器皆共用同一個數之子濾波信號。 The two-stage analysis filterbank of claim 5, wherein the combinations and rotators of each of the two analysis filterbanks are based on the same set of binomial weights and correspond to two combinations of any two adjacent subbands A sub-filtered signal that shares the same number with the rotator. 如請求項6之兩段式分析濾波器組，其中該二分析濾波器組之該二子帶響應預補償器之二頻率響應於各頻率之相位差為π/2的整數倍之固定值。 The two-stage analysis filter bank of claim 6, wherein the phase difference between the two frequency responses of the two subband response precompensator of the two analysis filter bank is a fixed value that is an integer multiple of π/2. 如請求項7之兩段式分析濾波器組，其中該低分析濾波器組中之最高中心頻率之子濾波器與該高分析濾波器組中之最低中心頻率之子濾波器具相同中心頻率與頻寬。 The two-stage analysis filter bank of claim 7, wherein the sub-filter of the highest center frequency in the low analysis filter bank and the sub-filter of the lowest center frequency in the high analysis filter bank have the same center frequency and bandwidth. 一種包括三個如請求項1之分析濾波器組之三段式分析濾波器組，該三分析濾波器組為一相應一低子帶組之低分析濾波器 組，一相應一中子帶組之中分析濾波器組，以及一相應一高子帶組之高分析濾波器組，該三分析濾波器組分別將一輸入信號作濾波分頻處理以產生多個子帶信號，該低分析濾波器組之該子帶響應預補償器之該線性濾波運算為一低通濾波運算，該中分析濾波器組之該子帶響應預補償器之該線性濾波運算為一帶通濾波運算，且該高分析濾波器組之該子帶響應預補償器之該線性濾波運算為一高通濾波運算。 A three-stage analysis filter bank comprising three analysis filter banks as claimed in claim 1, the three analysis filter bank being a low analysis filter corresponding to a low subband group group, an analysis filter group corresponding to a middle subband group, and a high analysis filter group corresponding to a high subband group, the three analysis filter groups respectively filter an input signal to generate multiple subband signals, the linear filtering operation of the subband response precompensator of the low analysis filter bank is a low pass filtering operation, and the linear filtering operation of the subband response precompensator of the middle analysis filter bank is A bandpass filtering operation, and the linear filtering operation of the subband response precompensator of the high analysis filter bank is a highpass filtering operation. 如請求項9之三段式分析濾波器組，其中該三分析濾波器組之每一者之該等組合與旋轉器基於同一組二項式權重，且相應任兩相鄰子帶之二組合與旋轉器皆共用同一個數之子濾波信號。 The three-segment analysis filter bank of claim 9, wherein the combinations and rotators of each of the three analysis filter banks are based on the same set of binomial weights and correspond to two combinations of any two adjacent subbands A sub-filtered signal that shares the same number with the rotator. 如請求項10之三段式分析濾波器組，其中該三分析濾波器組之該三子帶響應預補償器之三頻率響應於各頻率之相位差為π/2的整數倍之固定值。 The three-stage analysis filter bank of claim 10, wherein the phase difference of the three frequency responses of the three subband response precompensator of the three analysis filter bank is a fixed value of an integer multiple of π/2 in response to each frequency. 如請求項11之三段式分析濾波器組，其中該低分析濾波器組中之最高中心頻率之子濾波器與該中分析濾波器組中之最低中心頻率之子濾波器具相同中心頻率與頻寬，且該中分析濾波器組中之最高中心頻率之子濾波器與該高分析濾波器組中之最低中心頻率之子濾波器具相同中心頻率與頻寬。 The three-stage analysis filter bank of claim 11, wherein the sub-filter of the highest center frequency in the low analysis filter bank and the sub-filter of the lowest center frequency in the middle analysis filter bank have the same center frequency and bandwidth, And the sub-filter of the highest center frequency in the middle analysis filter bank and the sub-filter of the lowest center frequency in the high analysis filter bank have the same center frequency and bandwidth. 一種包括一個如請求項1之分析濾波器組之濾波器組 式系統，該分析濾波器組將一輸入信號作分頻濾波處理以產生多個子帶信號，該信號處理系統還包括：一個抽取器，其以一抽取倍率抽取該等子帶信號或其振幅以產生一輸入頻譜；一個核心數位信號處理單元，其將該輸入頻譜執行指定的數位信號處理以決定每一時間該等子帶信號相應之多個子帶權重；以及一個子帶組合器，其對該等子帶信號或其之實部以相應之該等子帶權重作一加權和運算以產生一輸出信號。 A filter bank comprising an analysis filter bank as claimed in claim 1 The analysis filter bank performs frequency division filtering processing on an input signal to generate a plurality of sub-band signals, and the signal processing system also includes: a decimator, which extracts the sub-band signals or their amplitudes at a decimation rate to generating an input spectrum; a core digital signal processing unit, which performs specified digital signal processing on the input spectrum to determine a plurality of subband weights corresponding to the subband signals at each time; and a subband combiner, which The equal sub-band signals or their real parts are subjected to a weighted sum operation with the corresponding sub-band weights to generate an output signal. 一種包括多個如請求項1之分析濾波器組之混合式信號處理系統，該等分析濾波器組分別將多個帶信號作濾波分頻以產生多個子帶信號，該混合式信號處理系統還包括：一個成幀與時-頻轉換器，其將一輸入信號依時間劃分成等長且等間距之多個信號幀，並將該等信號幀分別作一時-頻轉換以產生該等帶信號；一個抽取器，其以一倍率抽取該等子帶信號或其振幅以產生一輸入頻譜；一個核心數位信號處理單元，其對該輸入頻譜執行指定的信號處理以決定該等帶信號之每一者相應之多個子帶信號之多個子帶權重； 多個子帶組合器，其每一者將該等帶信號之一帶信號相應之該等子帶信號以其相應該等子帶權重進行一加權和運算以產生多個被修改帶信號之一被修改帶信號；以及一個頻-時轉換器，其對該等被修改帶信號相應同一時間之多個取樣點作一頻-時轉換以產生一輸出信號。 A hybrid signal processing system comprising a plurality of analysis filter banks as claimed in claim 1, the analysis filter banks respectively filter and frequency-divide a plurality of band signals to generate a plurality of subband signals, the hybrid signal processing system further Including: a framing and time-frequency converter, which divides an input signal into multiple signal frames of equal length and equal spacing according to time, and performs time-frequency conversion on the signal frames respectively to generate the band signals ; a decimator that extracts the subband signals or their amplitudes by a factor to generate an input spectrum; a core digital signal processing unit that performs specified signal processing on the input spectrum to determine each of the subband signals is the multiple subband weights of the corresponding multiple subband signals; a plurality of sub-band combiners, each of which performs a weighted sum operation on the corresponding sub-band signals of the one of the band signals with their corresponding sub-band weights to generate one of a plurality of modified band signals modified band signals; and a frequency-to-time converter that performs a frequency-to-time conversion on the modified band signals corresponding to a plurality of sampling points at the same time to generate an output signal. 一種相應多個子帶之濾波器組運算程序，其包括下列步驟：對一輸入信號之至少一取樣點進行一線性濾波運算以得到一響應預補償信號之至少一取樣點；將該響應預補償信號之該至少一取樣點進行中心頻率相異之多個複數型一階無限衝激響應濾波運算以得到多個子濾波信號，其每一子濾波信號包含至少一取樣點；以及從該等子濾波信號中選擇相應該等子帶之多個子集，其每一者包含相同個數、由中心頻率相鄰之至少二濾波運算得到之至少二子濾波信號，將該等子集之每一子集相應同一時間之至少二子濾波信號取樣點以一組二項式權重進行一加權和運算，並將該加權和運算結果隨相應子帶之中心頻率旋轉一相位以得到多個子帶信號之一子帶信號，其包括至少一取樣點。 A filter bank operation program corresponding to a plurality of subbands, comprising the following steps: performing a linear filtering operation on at least one sampling point of an input signal to obtain at least one sampling point of a response precompensation signal; The at least one sampling point is subjected to a plurality of complex first-order infinite impulse response filtering operations with different center frequencies to obtain a plurality of sub-filtered signals, each sub-filtered signal includes at least one sampling point; and from the sub-filtered signals Select a plurality of subsets corresponding to the subbands, each of which contains the same number of at least two subfiltered signals obtained by at least two filtering operations adjacent to the center frequency, and each of the subsets corresponds to At least two sub-filtered signal sampling points at the same time perform a weighted sum operation with a set of binomial weights, and rotate the result of the weighted sum operation by a phase with the center frequency of the corresponding sub-band to obtain a sub-band signal of a plurality of sub-band signals , which includes at least one sampling point. 如請求項15之濾波器組運算程序，其中相應兩頻率 相鄰子帶之二子濾波信號子集有至少一相同之子濾波信號。 The filter bank operation program of claim 15, wherein the corresponding two frequencies The two sub-filtered signal subsets of adjacent sub-bands have at least one identical sub-filtered signal. 如請求項16之濾波器組運算程序，其中相應兩頻率相鄰子帶之二旋轉相位差異為-π/2弧之整數倍。 The filter bank operation program of claim 16, wherein the difference of the two rotation phases of the adjacent subbands of the corresponding two frequencies is an integer multiple of -π/2 arc. 如請求項17之濾波器組運算程序，其中該等子帶設定為相等頻寬，且該線性濾波運算為該輸入信號與該輸入信號之一延時版本之一加權和運算。 The filter bank operation procedure of claim 17, wherein the subbands are set to be of equal bandwidth, and the linear filtering operation is a weighted sum operation of the input signal and a delayed version of the input signal. 一種包括一個執行一個如請求項15之濾波器組運算程序之步驟之濾波器組式信號處理程序，該步驟對一輸入信號之至少一取樣點執行該濾波器組運算程序以得到多個子帶信號，其每一者包括至少一取樣點，該濾波器組式信號處理程序還包括下列步驟：若一抽取周期結束，則抽取該等子帶信號或其振幅以得到一輸入頻譜，對該輸入頻譜執行一核心信號處理程序以決定該等子帶信號相應之多個子帶權重，並開始算一個新的抽取周期；以及對該等子帶信號相應同一時間之多個取樣點或其之實部以該等子帶權重進行一加權和運算以得到一輸出信號之至少一取樣點。 A filter bank signal processing program comprising a step of executing a filter bank operation procedure as claimed in claim 15, the step of performing the filter bank operation procedure on at least one sampling point of an input signal to obtain a plurality of subband signals , each of which includes at least one sampling point, the filter bank signal processing program further includes the following steps: if a decimation period ends, extracting the subband signals or their amplitudes to obtain an input spectrum, the input spectrum Execute a core signal processing program to determine a plurality of sub-band weights corresponding to the sub-band signals, and start to calculate a new decimation cycle; and a plurality of sampling points or their real parts corresponding to the sub-band signals at the same time are given by A weighted sum operation is performed on the subband weights to obtain at least one sample point of an output signal. 一種包括一個執行一個如請求項15之濾波器組運算程序之步驟之混合式信號處理程序，該步驟對多個帶信號分別執行一濾波器組運算程序以得到多個子帶信號，其每一者包括至少一取樣點， 該混合式信號處理程序還包括下列步驟：對一輸入信號之至少一信號幀分別進行一時-頻轉換運算以得到該等帶信號，其每一者包括相應同一頻帶之至少一頻譜取樣點；若一抽取周期結束，則抽該等子帶信號或其振幅以得到一輸入頻譜，對該輸入頻譜執行一核心信號處理程序以決定該等帶信號之每一者相應之多個子帶信號之多個子帶權重，並開始算一個新的抽取周期；將該等帶信號之每一者相應之該等子帶信號以其相應該等子帶權重進行一加權和運算以得到多個被修改帶信號之一被修改帶信號，其包括至少一取樣點；以及對該等被修改帶信號相應同一時間之多個取樣點進行一頻-時轉換運算以得到一輸出信號之多個取樣點。 A hybrid signal processing program comprising a step of executing a filter bank operation procedure as claimed in claim 15, the step of respectively performing a filter bank operation procedure on a plurality of band signals to obtain a plurality of sub-band signals, each of which includes at least one sampling point, The mixed signal processing program further includes the following steps: performing a time-frequency conversion operation on at least one signal frame of an input signal to obtain the band signals, each of which includes at least one spectral sampling point corresponding to the same frequency band; if Once the decimation period ends, the subband signals or their amplitudes are extracted to obtain an input spectrum, and a core signal processing procedure is performed on the input spectrum to determine a plurality of sub-band signals corresponding to each of the plurality of sub-band signals weighted, and start to calculate a new decimation cycle; the sub-band signals corresponding to each of the band signals are subjected to a weighted sum operation with their corresponding sub-band weights to obtain a plurality of modified band signals. A modified band signal includes at least one sampling point; and a frequency-time conversion operation is performed on a plurality of sampling points corresponding to the same time of the modified band signal to obtain a plurality of sampling points of an output signal. 一包含至少一處理器之信號處理系統，其中該至少一處理器對一輸入信號之至少一取樣點執行如請求項15至18中任一項濾波器組運算程序或如請求項19之一濾波器組式信號處理程序以得到一輸出信號之至少一取樣點，或者該至少一處理器對該輸入信號之至少一信號幀執行如請求項20之一混合式信號處理程序以得到該輸出信號之多個取樣點。 A signal processing system comprising at least one processor, wherein the at least one processor performs a filter bank operation procedure such as any one of claims 15 to 18 or a filter such as claim 19 on at least one sample point of an input signal a processor-type signal processing procedure to obtain at least one sampling point of an output signal, or the at least one processor executes a mixed-signal processing procedure as in claim 20 for at least one signal frame of the input signal to obtain a sample point of the output signal multiple sampling points. 一種相應多個子帶之分析濾波器組，其將一輸入信號 依該等子帶作濾波分頻以產生多個子帶信號，該等子帶為非等寬，該分析濾波器組包括：一子帶響應預補償器，其將該輸入信號作一線性濾波運算以產生一響應預補償信號，該響應預補償器於非等寬子帶組態下設定為使該響應預補償信號等於該輸入信號；中心頻率相異之多個子濾波器，其分別將該響應預補償信號作一複數型一階無限衝激響應濾波處理以產生多個子濾波信號；以及基於一組二項式權重之多個二項式組合與旋轉器，其每一者將至少二子濾波信號以該組二項式權重作一加權和運算，並將該加權和運算結果隨相應子帶之中心頻率旋轉一相位以產生該等子帶信號之一子帶信號，其中該至少二子濾波信號由該等子濾波器之至少二中心頻率相鄰之子濾波器產生。 An analysis filter bank corresponding to a plurality of subbands, which converts an input signal Perform filtering and frequency division according to the sub-bands to generate a plurality of sub-band signals, the sub-bands are of unequal width, and the analysis filter bank includes: a sub-band response pre-compensator, which performs a linear filtering operation on the input signal In order to generate a response pre-compensation signal, the response pre-compensator is set to make the response pre-compensation signal equal to the input signal under the unequal width sub-band configuration; a plurality of sub-filters with different center frequencies, respectively, the response The pre-compensated signal is subjected to a complex first-order infinite impulse response filtering process to generate a plurality of sub-filtered signals; and a plurality of binomial combinations and rotators based on a set of binomial weights, each of which converts at least two sub-filtered signals Perform a weighted sum operation with the set of binomial weights, and rotate the result of the weighted sum operation by a phase with the center frequency of the corresponding subband to generate a subband signal of the subband signals, wherein the at least two subfiltered signals are composed of At least two sub-filters with adjacent center frequencies of the sub-filters are generated.

• 2020
  • 2020-10-21 TW TW109136460A patent/TWI772930B/en active

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