[Ffmpeg-devel] [PATCH] vbr audio encode

Justin Ruggles jruggle
Sun Aug 14 07:10:55 CEST 2005

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

Here is an updated patch without normalized scale, and with added
support for faac.  But faac is weird.  It doesn't have CBR as an option
at all, only VBR or ABR.  When bitrate is set to zero, it uses purely
VBR based on the quality factor only.  But even the ABR is based
partially on the quality factor.  The result is that the '-ab' option
only really works accurately between about 100kbps and 200kbps for
stereo input.  The default quality of 100 limits the output bitrate
range.  It would be a nightmare to try to add support for adjusting both
bitrate and quality without breaking the intended function of other codecs.

You may notice that I changed the default bitrate to 128000 rather than
64000.  64kbps really makes no sense.  For stereo input, faac and lame
at 64kbps are nearly intolerable to listen to.  Vorbis sounds great, but
it's in a class by itself at this point.  Also, faac's bitrate field is
actually bitrate per channel.  I suspect this is why the default bitrate
was set to 64000 in the first place.

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