Hi
On Fri, Jan 05, 2007 at 07:56:41PM -0600, Ryan Martell wrote:
> Hi--
>
> I need to have a random for generating a GUID for mms streaming, and
> there also needs to be one for AC3 (right?). Michael suggested
> "a LFG or mersenne twister based av_random() for libavutil would
> certainly be welcome"
>
> I have tweaked some example source code, and have sent an email
> asking the author if he would allow it for inclusion; if not, I'll
> rewrite it based on the published formula.
>
> Does this an interface work for you:
>
> #define AV_RANDOM_PERIOD 624
i dont like that name at all, as its not the period of the generator
maybe simply AV_RANDOM_N would do or maybe calling it
degree of recurrence like wikipedia does ...
>
> typedef struct {
> unsigned int magic_cookie; ///< prevent someone from calling
> random without the state setup (sets it up automatically)
> unsigned long mt[AV_RANDOM_PERIOD]; ///< the array for the state
> vector
> int mti;
> } AVRandomState;
>
> void av_init_random(unsigned long seed, AVRandomState *state);
>
> unsigned long av_random(AVRandomState *state); // 32 bit random
> double av_random_real1(AVRandomState *state); // [0-1] as double
>
> Or would you rather have:
>
> AVRandomState *av_init_random(unsigned long seed);
> void av_free_random(AVRandomState *state);
>
> unsigned long av_random(AVRandomState *state);
this is closer to what i had in mind ...
though i would like av_random() to be in a header file and be static inline
as its likely called often, the function is pretty small and speed might
matter
also long -> int, POSIX gurantees that int is >=32bit
and avoid (u)int32_t in the code as it might be slow on some obscure
architectures
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Let us carefully observe those good qualities wherein our enemies excel us
and endeavor to excel them, by avoiding what is faulty, and imitating what
is excellent in them. -- Plutarch
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