Xpra: Ticket #615: 100% picture quality everywhere

At the moment, the default threshold which triggers a lossless refresh is set at 95%. This means that an h264 frame from x264 at 95% will not cause a lossless refresh despite the fact that the pixel data may be lower than we expect.

Although it may be possible to normalize the quality values better (so that a jpeg at 95% is closer to a webp or NVENC encoded frame at the same quality setting), ultimately we may just need to have 100% quality everywhere:

To achieve this, we may need:

Sat, 19 Jul 2014 20:42:05 GMT - Antoine Martin: owner, status, description changed

Sat, 17 Jan 2015 10:00:36 GMT - Antoine Martin: owner, status changed

A lot of improvements have been made in this area:

See also #620

TIL: we now refresh anything that is not lossless (was 95% previously): done in r8491 (+blooper fixed in r8492), backport in r8493.

Regions that are lossy and did not refresh should have been pretty rare because we tend to go to 100% quality when the quality is high (to avoid having to do the refresh), but can still happen with video encodings.

Note: this is a pretty significant change, hopefully without undesirable side effects... but maybe the heuristics will need to be tuned further now that we have more refresh needs when using high quality video.

@afarr: please close as an ack. Feel free to test and try to verify that it is impossible to get lossy regions to stick on screen for too long.

Sat, 24 Jan 2015 01:44:14 GMT - alas: status changed; resolution set

Wasn't able to get any lossy regions to stick for anything more than a fraction of a second (but wasn't using 4K monitor...), whether there was any subregions painting with h264 or not.

I'll go ahead and close.

Sat, 23 Jan 2021 05:00:57 GMT - migration script:

this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/615