[FFmpeg-devel] [PATCH] mp4toannexb modification / improvement

Luca Abeni lucabe72
Fri Jun 4 13:34:06 CEST 2010

On 06/04/2010 11:15 AM, Luca Abeni wrote:
>>> why does the bsf not convert the extradata?
>>> i mean it leaves the extradata in "AVC" syntax
>> I do not know... My impression is that since the bsf "inlines"
>> the SPS and PPS (inserting them in the bitstream) it does not care
>> about converting the format of the extradata. But I am not sure;
>> maybe Benoit can clarify this point?
> BTW, if modifying the extradata is the right thing to do, I can provide
> a patch doing so.

I tried this approach (and it actually simplifies the code :).
But it causes problems with "-vcodec copy", because the bitstream
filter is passed the output context, which contains a reference to
the input context extradata
(see ffmpeg.c at line 2171: "codec->extradata= icodec->extradata;")

The bitstream filter reallocates the extradata, so the output codec
context contains the new pointer, but the input codec context still
contains a pointer to the "original extradata". As a result,
at line 610 ends up tring to free a wrong pointer.

Which kind of solution do you prefer? Changing line 2171 in something
that allocates memory for the "output extradata", and copies the input
extradata in this new buffer?


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