[Ffmpeg-devel] [PATCH] vbr audio encode

Michael Niedermayer michaelni
Sat Aug 13 18:15:14 CEST 2005


On Sat, Aug 13, 2005 at 12:40:13AM -0400, Justin Ruggles wrote:
> 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.

a normalized scale if you want to add one should have the property that
value X for one encoder gives approximately the same quality as value
X for another encoder, that also contradicts a default == 128 rule

iam not sure though if this is worth the work, maybe we should just
drop the normalized scale support idea ...



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