[Ffmpeg-devel] Shorten audio FourCC

Måns Rullgård mru
Tue Oct 10 01:22:54 CEST 2006

Roberto Togni said:
> On Mon, 9 Oct 2006 20:04:42 +0100 (BST)
> M?ns Rullg?rd <mru at inprovide.com> wrote:
>> Diego Biurrun said:
>> > Shorten audio is not yet supported by MPlayer since it lacks a FourCC in
>> > libavformat/riff.c.  Now adding one would be easy, but the question is
>> > which one to choose.  The obvious choice would be 'shn', but that's just
>> > three characters.  So maybe 'shor' or 'shn '.
>> >
>> > Then again, in libavcodec/shorten.c is the following code snippet:
>> >
>> >   /* shorten signature */
>> >   if (get_bits_long(&s->gb, 32) != bswap_32(ff_get_fourcc("ajkg"))) {
>> >   av_log(s->avctx, AV_LOG_ERROR, "missing shorten magic 'ajkg'\n");
>> >
>> > Does 'ajkg' have any further relationship with Shorten?  Should it be
>> > used as the FourCC?
>> RIFF files use 16-bit IDs for audio.  Adding a bogus 32-bit ID there to work
>> around design limitations in mplayer is unacceptable IMO.
> MPlayer can happily work also with 16-bit identifiers. But FOURCCs are
> used by most formats, and look "better" than a random 16-bit IDs.

You're missing the point.  The file riff.c contains mappings between ffmpeg
CODEC_ID_* values and IDs used in RIFF-type files (AVI and WAV mainly).  This
should not be abused as a place for mappings between ffmpeg CODEC_ID_* and
mplayer internal numbers.  This becomes even more an abuse when the numbers
chosen are impossible to use in RIFF files.

M?ns Rullg?rd
mru at inprovide.com

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