[FFmpeg-devel] [PATCH] libmp3lame: set noise shaping & psycho acoustic algorithms quality

Nicolas George nicolas.george
Thu Jul 31 18:07:19 CEST 2008

Hi. Thanks for your answer.

Le quartidi 14 thermidor, an CCXVI, Robert Swain a ?crit?:
> The AAC profiles (as all MPEG profiles) affect the bitstream features
> used.

Yes, I had thought of that. I do not think that is actually a problem. That
would have probably been a problem if it were the other way around, bit in
this case I think it is ok.

>	It seems to me (at first glance) -q is more analogous to -*cmp
> or -dia_size for video or subq/subme in x264. I'm not sure if we have
> an appropriate option for audio speed/compression efficiency tradeoff.

I browsed all existing options, keeping only the ones tagged "E.VA." and
"E..A.", and -profile was the best I found. I saw -compression_level you
suggest in your other mail, but it is always used for lossless compression,
so I thought it would be misleading.

In fact, I am deeply unsatisfied by the option system. The way things work
right now, you can put "-level 42" in your command line and have it silently
ignored, just because the selected codec do not use the level field.
Silently ignoring an option is bad.

I am not sure what could be done instead. Maybe a codec-specific option
system would be better. Something like:

ffmpeg ... -acodec libmp3lame:q=3:aq=2 ...

I am not sure.


  Nicolas George
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