So I’m stubbornly plugging away at my toy VP8 encoder and I managed to produce this gem. See if you can spot the subtle mistake:

The misplaced color plane resulted from using the luma plane stride where it was not appropriate. I fixed that and now chroma planes are wired to use to the same naive prediction algorithm as the luma plane.

Also, I fixed the entropy encoder so that end of block conditions are signaled correctly (instead of my original, suboptimal hack to just encode all zeros). I was disappointed to see that this did not result in a major compression improvement. Then again, I’m using the lowest possible quantization settings for this outing, so perhaps this is to be expected.

Sigh… 4×4 luma prediction is next. Wish me luck.