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Superblock Corner Cases

April 20th, 2007 by Multimedia Mike

Look who has been playing around some more with the vector drawing program. Here’s an illustration of somewhat limited utility but that still demonstrates an important point of the VP3/Theora coding scheme:

VP3/Theora superblock traversal corner cases

The image above depicts a hypothetical frame in the VP3/Theora coding scheme that has sample dimensions of 88×48. The valid 8×8 fragments are depicted in green. Since these do not line up nicely on 32-sample superblock boundaries, round up to the nearest superblock in either dimension. The green fragments inside the turquoise zone are the visible fragments. The grey fragments are phantoms that still must be accounted for in the overall superblock traversal pattern when coding/decoding the transform coefficients.

There is also the matter of what happens when the width and height of the frame do not line up on fragment boundaries (i.e., are not divisible by 8). The image is rounded up to the nearest fragment size for the purpose of transform coding.

Posted in Open Source Multimedia, VP3/Theora | 1 Comment »

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