[theora-dev] More Missing Pieces

Mike Melanson melanson at pcisys.net
Mon Feb 24 13:15:43 PST 2003

On Mon, 24 Feb 2003, Dan Miller wrote:

> umm, that's a good question.  I guess it's the same problem as with Vorbis; I hadn't really thought about this.  I think all these formats have some sort of codec-specific stream header data, don't they?

        AVI/ASF files transport the standard Windows bitmapinfo header
structure which can tack on extra data at the end. QT has the video 'stsd'
atom which can have similar data at the end. The most common extra data I
see is palette information. HuffYUV also transports codec tables inside
AVI bih structures. We would just need to define the layout of such a
structure for Theora data. Something like:

  2560 signed 16-bit numbers for the 80 histograms (which byte order?)
  64 QThresh table values (8- or 16-bits?)

        As an aside, does anyone know how to decode Vorbis audio data
encapsulated within a Quicktime file? Do I need to pull some information
out of the audio stsd atom? I have a few Vorbis/QT samples made from the
Heroine Warriors' programs but I have never heard audio from them.


	-Mike Melanson

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