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

Mats Peterson matsp888 at yahoo.com
Mon Jan 4 22:36:10 CET 2016

On 01/04/2016 10:34 PM, Hendrik Leppkes wrote:
> On Mon, Jan 4, 2016 at 10:17 PM, Mats Peterson
> <matsp888-at-yahoo.com at ffmpeg.org> 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.
>> I have also removed some superfluous checks for the format/fourcc at the
>> very start of the private data for A_QUICKTIME and V_QUICKTIME. This
>> shouldn't happen, since the private data always starts with the sample
>> description size, *then* the format/fourcc, in a Matroska file.
> Don't remove any existing checks, they usually get added based on actual files.
> "Should not" does not mean "does not".
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Well, I almost expected that answer, Hendrik. Thanks. But a file with 
the fourcc at the very start will break things later on. Hopefully these 
files are very few ;)


Mats Peterson

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