[FFmpeg-devel] Patch - Allow disabling of bit reservoir when encoding MP3 audio

Paul Kelly paul
Tue Feb 5 09:47:11 CET 2008

On Tue, 5 Feb 2008, Michael Niedermayer wrote:

> Splitting mp3 at frame boundaries should not cause artifacts. If it does
> submit a bugreport to whatever decoder you use. If its libavcodec, ill fix
> that if you provide such a file with artifacts at the start.

It was in mplayer; perhaps libavcodec doesn't exhibit the artefacts but 
IMHO that is not really the point because some data (i.e. the bits 
belonging to the first frame after the split that had been encoded in 
previous frames) is still lost and that is because of the encoder's 
behaviour, not the decoder. Quoting from the lame manpage:

         Disable the bit reservoir.  Each frame will then become independent
  from previous ones, but the quality will be lower."

I think the lower quality (how much, really?) is irrelevant with constant 
bitrate as a higher bitrate could simply be used if quality was important. 
Having each frame independent from previous ones is (as you suggest) an 
important advantage.

On Tue, 5 Feb 2008, Rich Felker wrote:

> Personally I would say just always disable bit reservoir. It's a dumb
> [mis-]feature. If VBR is desired then use honest VBR mode, not this
> ugly hack of coding bits into the wrong frames...

That solution is also fine by me - relevant patch attached.

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