[FFmpeg-devel] [PATCH v2] lavf/matroskadec: A_QUICKTIME and AV_CODEC_ID_NONE

Mats Peterson matsp888 at yahoo.com
Tue Jan 5 11:57:58 CET 2016

On 01/04/2016 10:49 PM, Mats Peterson wrote:
> In many older QuickTime files, the audio format, or "fourcc", is
> 0x00000000 (AV_CODEC_ID_NONE). The QuickTime File Format Specification
> states the following regarding this situation:
> "This format descriptor should not be used, but may be found in some
> files. Samples are assumed to be stored in either 'raw ' or 'twos'
> format, depending on the sample size field in the sound description."
> MPlayer handles this logic by itself, but FFmpeg/FFplay currently does
> not.
> Mats
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> ffmpeg-devel mailing list
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I'm still a bit afraid about the following construct for both 
A_QUICKTIME and V_QUICKTIME. It could lead to false positives. The fact 
is that the format/fourcc ALWAYS starts at offset 4 of the private data 
in a Matroska file. Does anyone sit on a file where it does not?

if (ff_codec_get_id(ff_codec_movaudio_tags, 
AV_RL32(track->codec_priv.data))) {
    fourcc = AV_RL32(track->codec_priv.data);
    codec_id = ff_codec_get_id(ff_codec_movaudio_tags, fourcc);

Mats Peterson

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