[FFmpeg-devel] Gain control not yet implemented

[Pascal Massimino]

On Nov 29, 2007 10:16 AM, Gabriel Teixeira <gabrieldiegoteixeira at gmail.com>
wrote:

> Hi,
>
> I developed a application that uses the libavcodec, but only after
> some months of development and testing appeared a weird message that I
> never got before:
> [mpeg4aac @ 01290000]faac: frame decoding failed: Gain control not yet
> implemented
> Since the audio was encoded with ffmpeg, I believed this frame
> wouldn't have gain control or any stuff that ffmpeg could not decode.
> This audio stream was sent over the web via multicast, so may be a
> fail in the information transported. Anyway, how to identify and
> correct this problem?
>

  this is a bug in FAAC: scale factor differences must be in range [-60,
59],
 but faac can generate such big differences, and then writes
 invalid huffman codes (cf huffman.c, WriteScalefactors()).
 So you end up with invalid bitstreams.
 This bug has been reported a long ago, a patch proposed, but wasn't
 committed in cvs. Now, even the web page disappeared, so i can't
 even find back the patch. I'll see if i can resurrect something on my
 attic...

skal


> Thanks in advance
> Gabriel
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