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Starred by 6 users

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Status: Duplicate
Merged: issue 966
Owner: ----
Closed: Jan 2018

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Motion vector size limits cause quality loss on very high resolutions

Reported by, Nov 17 2016

Issue description

AV1 currently allows coding motion vectors residuals with a full pixel size of 11 bits (i.e. -2047-2047). This means if an object moves across the image with a motion vector above that size, this cannot currently be represented in the bitstream.

If the image size is significantly above 2k (e.g. 4k or 8k content), this presents an issue. Therefore, it would be nice if the limit could be increased or removed for AV1. Even cooler would be to make the limit depend on the frame size.
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Comment 1 by, Nov 30 2016

Labels: -Type-Defect Type-Enhancement
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Comment 2 by, Nov 30 2016

Labels: Hotlist-AV1-must-fix
In case of multicore decoding implementation (for ex. h/w, single tile/slice) 2 cores could decode in parallel with 11bit hight distance, but if make maximum limit, than only single core could do it. I don't think, 8K like, frame size are suitable for SW decoding. Where is no big adventure to use fast motion Inter blocks, rate control can't catch such big motion in real life.
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Comment 4 by, May 9 2017

Status: Available (was: New)
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Comment 5 by, Jan 4 2018

Mergedinto: 966
Status: Duplicate (was: Available)

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