[FFmpeg-devel] [PATCH] LGPL AC3 decoding
Tue May 19 09:26:38 CEST 2009
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.
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