Lines sometimes appear on smooth areas at the top of the
picture when coding 720p material with -HD720 preset.
The artefacts look like some sort of error in the overlapping
process. HD720 presets have non-square blocks, and so a
possible cause is that x- and y- block parameters are
The error may be confined to Intra blocks, but it's hard to
Initially, the preset has been changed to use square blocks
to avoid the problem.
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