[Ffmpeg-devel] 4XM audio codec_tag

[Michael Niedermayer]

Hi

On Mon, Nov 06, 2006 at 01:33:54PM -0000, M?ns Rullg?rd wrote:
> 
> Michael Niedermayer said:
> > Hi
> >
> > On Mon, Nov 06, 2006 at 02:55:14AM +0000, M?ns Rullg?rd wrote:
> >> Diego Biurrun <diego at biurrun.de> writes:
> >> > So please remind me: What is the problem with storing arbitrary
> >> > audio and video formats in multimedia containers, especially generic
> >> > ones?
> >>
> >> The format needs to be able to store global headers (aka extradata),
> >> and it needs some way of identifying the codec.  The extradata part is
> >> easy: either there is a place for it or there isn't.  If the format
> >> can't accommodate an extradata chunk, codecs that need it can't be
> >> used.  To identify the codec, format specifications typically include
> >> a list of tag/codec pairs.  Any codec in this list can be stored using
> >> the format in question.  If the codec is not in the list, it is of
> >> course possible to invent a tag.  The problem with this approach is
> >> that nobody else will know what this tag means, and thus nobody else
> >> will be able to play the file.  Is this really so difficult to
> >> understand?
> >
> > yes, a codec has a name, and often a fourcc which is used in many
> 
> Wrong.  A codec has a name.  A fourcc is not an inherent property of a
> codec.  It is something that might be used to identify it in one particular
> file format.  If a file format does not specify a fourcc/tag for some
> codec, that codec can't be portably used in that file format.  Period.

then why do so many codecs work in avi? they arent in the standard table
from ms, and still many different applications can mux and demux them
(= proof by contradicton)

[...]

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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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