[Ffmpeg-devel] [PATCH] vbr audio encode

[Justin Ruggles]

Hello,

The patch for vbr audio is pretty much ready.  From what I can tell, the
only codecs that support vbr are all external to ffmpeg (vorbis, lame,
faac).  After this, I might revisit simplifying the work I was doing on
adding vbr to ffmpeg's ac3 encoder, but that's for another day.

I did implement both normalized & codec-specific quality scales.  The
normalized scale follows a similar pattern as video quality, using 0.01
to 255.  The options I chose were '-aq' for normalized, and '-aqc' for
codec-specific.

The guideline I've used is to scale the normalized value to codec value
by holding to 0.01->best, 255->worst, and 128->default.  This can result
in a non-linear scale, but keeps uniformity of intent across codecs when
using the normalized scale.  A linear scale actually works for lame, but
that won't always be the case.

For now I have only implemented functionality for mp3 encoding, but I
wanted to submit the patch for responses before I add faac and vorbis.

-Justin
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