[FFmpeg-devel] [RFC] AAC Encoder, now more optimal
Sat Sep 6 22:50:51 CEST 2008
Kostya a ?crit :
> It is slower than realtime since it uses search for optimal quantizers
> for given quality.
> Any comments, suggestions, speedup tricks are extremely welcomed
> (especially the latter).
Hum...do you also plan on having an encoder really useable, or only an
optimal but unpractical one?
Speedups: well, except some heuristics and early terminations here and
there, a major speed hit is likely because of your quantization function.
A trivial convertion from float to integer is painfully slow with x86
Within LAME, Takehiro Tominaga implemented a nice trick to perform the
quantization using an union over float and int. You can check it within
takehiro.c, within #ifdef TAKEHIRO_IEEE754_HACK, quantize_lines_xrpow.
It's basically playing with the internal representaion of ieee754 floats
in order to do the float to int conversion in place within an union,
without any direct cast.
personal page: http://gabriel.mp3-tech.org
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