[x265] Encoding question

[Sebastian Sylwan]

Hi,

This is my first message to the list, so please forgive me if it is not
fully appropriate for it.

I am experimenting with encoding video whose final application is to be
merged with static images around it. I have reached an appropriate level of
compression, but I am seeing some quantization issues at the edge of the
frames, that would probably be perceptually ok, if they weren't adjacent to
a static image that is supposedly blended to the video. This is really only
noticeable in the darker areas of the image, and in regions that are
static, and the artifact is mostly noticeable since there is a tinting
towards green (and a slight brightening).

I was wondering if there is a way to tell the encoder to quantize less
aggressively around the edges (or in any specific area). Alternatively,
also biasing the quantization towards the darker regions of the image may
work. Since the artifacts seem to build overtime, I wonder if there is a
drifting of a DC component also happening.

Any suggestion appreciated. Of course I could increase the bitrate, but the
rest of the image is ok.

Thank you.

S
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