[Theora-dev] Directshow filters 0.64.7923

Timothy B. Terriberry tterribe at vt.edu
Sat Oct 9 10:24:04 PDT 2004

> The yOffset is wrong, though. With this theora block for decoding, the result 
> is as seen on http://www.huitl.de/theora/wrong-yoffset.jpg. I get correct 
> results using this formula:
> xOffset = width % 16
> yOffset = height % 16
> For the example shown above, yOffset will then be 8. With resolution 320 x 
> 240, yOffset will be 0 and this seems to be correct, too.

This is probably a confusion over whether yOffset is counted from the 
top or from the bottom of the image (I actually forget which way is 
which in the reference library). Also, note that both xOffset and 
yOffset should be made even by the encoder to make chroma siting work as 
expected. See Chapter 4 of the spec for details.

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