[FFmpeg-devel] [PATCH] LGPL AC3 decoding
Wed May 20 00:59:11 CEST 2009
On Tue, May 19, 2009 at 05:29:35PM -0400, Jason Garrett-Glaser wrote:
> On Tue, May 19, 2009 at 3:26 AM, Diego Biurrun <diego at biurrun.de> wrote:
> > On Mon, May 18, 2009 at 08:38:56PM -0400, Justin Ruggles wrote:
> >> Jason Garrett-Glaser wrote:
> >> > This patch contains a clean-room-written
> >> > ac3_decode_transform_coeffs_ch, written solely from the spec and
> >> > Justin's copious advice and descriptions (no knowledge of the original
> >> > function). ?Oddly enough, it seems to actually be closer to the
> >> > original liba52 code, despite the fact that I never saw that either.
> >> > According to Diego, this should be sufficient to finally LGPL ffac3;
> >> > I'll let someone else handle the header/configure changes for that.
> >> >
> >> > Bonus: mine's faster, too. ?With GCC 3.4 on 32-bit Core 2 Conroe
> >> > (First 1234901 bytes of Broadway-5.1-48khz-448kbit.ac3):
> >> >
> >> > Before: 27908.6 dezicycles (+/- 9.7)
> >> > After: 24820.6 dezicycles (+/- 12.4)
> >> > Total: 12.4% faster ac3_decode_transform_coeffs_ch
> >> >
> >> > PSNR-wise it matches the original exactly; this was achieved through
> >> > Justin supplying me with the single line of code for the bap=0 noise
> >> > from the original code. ?Note that I have not tested this on anything
> >> > other than that sample of Broadway, so I cannot guarantee it works for
> >> > all files.
> >> It looks good to me. ?I tested it out on a few other files and also got
> >> identical results.
> > Excellent! ?Somebody commit this, I'll handle the rest.
Build system and documentation adjusted.
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