Video compression technologies are about reducing and removing redundant video data so that a digital video file can be effectively sent over a network. With efficient compression techniques, a significant reduction in file size can be achieved with little or no adverse effect on the visual quality. The video quality can be affected if the file size is further lowered by raising the compression level for a given compression technique.
Generally RLE is used after quantization. RLE step re-arranges the quantized data in a format that reduces data redundancy in bit stream. For run length encoding, the 8x8 block should be scanned into 64-entry array in a zigzag fashion, as shown in figure1.
Figure1: Zigzag scanning
The block, which has now become a 64 entry, should next be manipulated using a modified run-length encoding algorithm transforming it into a series of integer pairs consisting of a run component and a signed level component. The run integer represents the number of zero entries preceding a level value in the array. The final run of zero entries in the array ends at the 64th block entry and not with a signed level- this reality is encoded as End of Block. The syntax as shown in Figure2.
Figure 2: Sample block Run length coding.
Author - Hemika Yadav
Intern Design Engineer at Silicon Mentor)
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