[Ffmpeg-devel] 4XM audio codec_tag

[Måns Rullgård]

Reimar D?ffinger <Reimar.Doeffinger at stud.uni-karlsruhe.de> writes:

> Hello,
> On Sun, Nov 05, 2006 at 09:00:14PM +0000, M?ns Rullg?rd wrote:
>> Does any of the above make sense to you?
>
> It's mostly about getting something more specific than whether it makes
> sense.

I just don't understand how you guys can find it so unimportant to be
accurate.  Ever heard of interoperability?

> Well, so far I think we can agree that
> 1) audio fourccs should go.

For RIFF based formats, yes, since storing them there is impossible.
In MOV audio uses 4-byte tags, and the two-byte RIFF tags would be
meaningless if stored there.

> 2) duplicate tags should be avoided if possible (though this should not
> be relevant for the MPlayer part of the discussion).

How many times do I have to repeat it?  Sharing the tables is only
acceptable if they are *defined* to be identical.  A few of the
entries being the same by coincidence is not a reason to share the
entire table between formats.  Duplicating those few table entries is
not a problem in my view.  The size of the tables is still small
compared to the full library.

> I on the other hand was mostly thinking of completely new formats, like
> all of those game formats, that do not usually appear in AVI.
> E.g. if the line
> vst->codec->codec_tag = MKTAG('R', 'J', 'P', 'G');
> was removed from nuv.c (which it probably should), then should an entry
> for it be added to riff.c?

I'd say no.  We have no choice but to include some nonstandard tags if
we want to support all the files out there.  That does not mean we
should be contributing to the mess.

> MPlayer has long supported that format in avi I think,

So what?

> I would tend towards: better clutter the table a bit and support more
> formats however rare than having a cleaner table.

Again you've drifted from the question of sharing the codec ID table
between unrelated formats, and treating the RIFF table as some kind of
absolute reference.

Just face the facts: formats use different tags to identify codecs, no
matter how much you pretend that all of them use the RIFF values.  The
only way to properly handle this is by using one codec tag table per
format.  End of story.

-- 
M?ns Rullg?rd
mru at inprovide.com