[Theora-dev] Directshow filters 0.64.7923

Timothy B. Terriberry tterribe at vt.edu
Sat Oct 9 12:31:35 PDT 2004

> OK... just curious why files that were apparently created with the 
> latest release, seem to work with centred offsets but not with offsets 
> at the top or bottom ?

Perhaps I'm not being clear: by "offset from the bottom" I mean that you 
take the offset, and count that many pixels from the bottom, and that's 
where the image begins. Similarly for "offset from the top". The actual 
number of pixels you have to count is stored in the bitstream. It is 
specified by the encoder, not the decoder. The current encoder is 
specifying half the number of extra pixels needed, which "centers" the 
image, but it is free to make it flush with the top, flush with the 
bottom, off-center, etc. The offset of the image is still stored in the 
bitstream counting from the bottom of the frame in each case.

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