color error when using opengl shaders for chroma conversion (480p only)

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What steps will reproduce the problem?
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What is the expected output? What do you see instead?

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Original issue reported on code.google.com by `boss...@yahoo.fr` on 22 Aug 2012 at 5:23

The issue provides no reproduction steps, expected output, files, tests, or entry points. Start by recovering a 480p OpenGL-shader chroma-conversion reproduction and compare it with other resolutions; done means the color error no longer occurs at 480p and the relevant regression is covered.

Written by the indexing model from the issue text.