[MPlayer-dev-eng] MPCF Draft/Discussion (MPlayer ContainerFormat)

michael c mrcole20 at hotmail.com
Fri Feb 7 15:54:21 CET 2003


Michael Niedermayer wrote:
>but whats the difference between a new fourcc & a new 64bit startcode?
>its the same, except that the fourcc adds another layer which isnt
>needed, and we should allso update the docs for a new fourcc if its
>used in such a way as for new packet, or its an undocumented feature
>and it would cause interoperability problems, i mean there are more
>players then 1 so it must be documented or others have to guess /
>reverse engeneer it, this isnt acceptable

hmm, forget the details of the implementation for a second. the 
universal_packet could as well start with a different sort of id or so. or 
certain fourccs would be kept internal. the point is that the packet would 
be universal and could be used for anything (except video/audio/(subs)). and 
the type of the data is described by that id.

i must disagree with the documentation part though. it makes absolutely no 
difference IMHO whether you document a whole new packet type, or the 
structure of the data section for a specific id.
actually when you create a new packet type for more things to add, as you 
suggested could happen (menu? chapters? whatever), demuxers that don't know 
these yet might run into problems - it will probably be easier for them just 
to skip universal packets with ids they dont know. i call this (contrary to 
your statement) better interoperability, because the demuxer is prepared 
from the beginning on to face things (packet ids) he never heard of 
(possible extensions to the format), and knows how to handle them.
and like i mentioned earlier, universal packets give you the power to add 
almost any kind of feature later, at almost no cost and remaining backwards 
compatible - still allowing players that never heard of those advanced 
features to play the file.
i just think it would be a mistake to close the door on that. new features 
WILL be wanted sooner or later, it's always been like that :-) the format IS 
supposed to be extensible and flexible after all, isn't it?


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