At 18:33 +1000 10/04/07, Silvia Pfeiffer wrote:
Recent discussion at Xiph around http://www.ietf.org/rfc/rfc4281
suggests the use of the following parameters:
# application/ogg; codecs="theora, vorbis" for Ogg Theora/Vorbis files
# application/ogg; codecs="theora, speex" for Ogg Theora/Speex files
# application/ogg; codecs="vorbis" for Ogg Vorbis files
sounds good;
and also use the disposition parameter:
# application/ogg; disposition=moving-image; codecs="theora, vorbis"
# application/ogg; disposition=sound; codecs="speex"
what is the 'disposition' parameter?
We did have the discussion over profiles of these codecs; I
understand profiles
are not used, but I am still unclear as to which of the following is true:
a) features are never added to the bitstreams, so any release of the decoder
will decode bitstreams made by any release of the encoder (modulo bugs);
b) the decoder release needed is signalled somehow in the bitstream
('need at
least the April 2005 release or later to decode this file')
c) neither of the above are true, it's left to the users to stay up
to date, and if
they don't, then, well, that's their problem.
In reply to this: Xiph has very carefully created and frozen (1st June
2004) a definition of the theora codec bitstream format, which should
be persistent for a while to come. So, while it is possible that there
may be new features added, it is not currently a consideration. There
are still multiple rounds of software optimisation possible to theora
encoders before they will require a change to the bitstream format.
For the case of a bitstream format change, there is version
information in the header of a theora bitstream. Major and minor
version numbers are being used similarly to the way that *nix library
version numbers work - anything with a minor change is backwards
compatible, but a major change may not be. So, if a major version
number change was to occur with theora, a new MIME type would probably
be required, e.g. video/x-theora2.
I hope this answers the question?
Yes, at least for Theora. Thank you!
--
David Singer
Apple Computer/QuickTime
