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

[Hendrik Leppkes]

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".