[vorbis] putting the video into ogg multimedia

[Ralph Giles]

With both vorbis and libmng nearing stable status, I've been thinking
about combining the two to make a real multimedia format. What would be
involved in embedding mng in an ogg bitstream? From what I've read of the
documentation, there doesn't seem to be any codec-enumeration system. Do
we just interleave the packets and let the player guess based on the
headers which codec to try? I suppose that works so long as the spec for
the multimedia files has a well-defined list of what is to be supported.

Practical motivation:

MNG is open, free, unencumbered and seems to have a clue in terms of
well designedness so it's a good match. While it doesn't provide
high compression ratios for video sources, it supports both completely
lossless and motion-jpeg encoding. In my mind that makes it an excellent
source or editing format for digital video. This would probably also
require an option for uncompressed audio; I suppose the pcm .wav header
could be abused for this purpose.

MNG was also designed as an animation format and should achieve good
compression of both traditional (2D) animation and "talking-head" video
where localized motion occurs over a static background. I think there's a
lot of room here for creatively-lossy compression research, some of
which might be applicable to the free video codec.

Finally, I agree with DVD-video's use of graphic overlays for subtitling
(though the text should also be available in a separate stream) most
particularly for the annotative possibilities. So even when there is an
Ogg video codec, I'd still like to see support for transparent mng
overlays.

Tying all this together seems to require some stream-description metadata.
I guess that's another way to handle codec identification. How's work on
that progressing? I see a need for (multiple) text/xml streams for
lyrics/subtitling/commentary in both the audio and video formats as
well, which should probably be separate from the meta-data.

In short, I feel the combination of mng and vorbis would go a long way
towards a useful multimedia format in the near term, even without a
vorbis-comparable video codec.

Comments please,

 -ralph


--
giles at ashlu.bc.ca
i read this list through the archives

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