[FFmpeg-devel] CNG (consistent noise generation) patch for AC-3 decoder

[Michael Niedermayer]

On Fri, Sep 02, 2016 at 01:13:33PM -0700, Jonathan Campbell wrote:
> 
> On 09/02/2016 01:01 PM, Michael Niedermayer wrote:
> >On Fri, Sep 02, 2016 at 10:19:23AM -0700, Jonathan Campbell wrote:
> >[...]
> >>CRC computation isn't fast enough? What should I use then? A sum of
> >>byte values?
> >av_lfg_init() calls av_md5_sum()
> >av_md5_sum() is too slow to be called per ac3 frame
> >
> >[...]
> >
> >
> >_______________________________________________
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> >ffmpeg-devel at ffmpeg.org
> >http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> Then for this to work at better performance, I'm going to have to
> either directly modify the AVLFG struct state (probably not a good
> idea), or add a function to libavutil/lfg.c that allows "fast
> seeding" without the use of MD5 which could probably be something as
> simple as copy the 32-bit seed 16 times through c->state[] with or
> without modification during the loop. Sound good?

yes, something like this
probably spliting the input into 16 parts get 16 CRCs and use them
instead of replication is probably better


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

You can kill me, but you cannot change the truth.
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