https://bugs.kde.org/show_bug.cgi?id=497435
--- Comment #18 from Ron <kdenlive-b...@contact.dot-oz.net> --- Ok, I had a chance to poke around with this some more - I figured bisecting mlt to find the exact change that introduced this problem shouldn't be too hard - but as usual I learned more than I bargained for :) The initial results didn't make a lot of sense at first, so I've attached another test project which is the same as the first one, implementing the test Roxane described, but as a 1080p native project instead of rescaling from 4k to eliminate any effect ffmpeg rescaling might have ... And interestingly, it appears there are two problems with the newest versions. Re-running the set of tests from scratch with this new project, the first curious thing I saw was that if I created rendering scripts with 22.08.1, 22.08.2, 24.12.0 and the 25.03.70 snapshot posted here for testing, then rendered them with melt from the 22.08.1 appimage, the result was, somewhat confusingly: - Both 22.08 scripts rendered 'perfectly', with the absolute minimum of jitter seen in any test. - The 24.12 and 25.03 scripts both rendered a jittering result, even with 22.08.1 melt. The difference in the later scripts which is causing the appearance of jitter appears to be 'rescale="hyper"' in the <consumer> options, even when there is no 'scale' option (and rescaling was disabled in the render dialog). If I remove that option, then the render script generated by both later versions renders perfectly with the 22.08.1 version of melt. So from that baseline, I could go back to more sanely bisecting mlt, and the result there confirmed what I originally suspected: The last commit to run this test with "no jitter" is this one: https://github.com/mltframework/mlt/commit/c2339fc146898197b11e13c44692d901ae436245 The next commit after that introduces some jitter: https://github.com/mltframework/mlt/commit/0c22797bbcb209f9667d72d4038866f28a624115 And the one after that makes it a bit worse: https://github.com/mltframework/mlt/commit/d047879e00f03b42587e68652dfe069c45c157aa The mlt version included with 25.03.70 still has a significant jitter compared to the 22.08.1 / mlt-c2339fc1 baseline. I'm still not exactly sure what problem those commits above were fixing, so I'm not terribly confident to propose another patch for mlt offhand that wouldn't re-introduce it - but I'm set up to test this now, so I can pull changes from mlt git or apply patches manually to test against this set of rendering scripts. I'm not quite sure what to suggest for the rescale="hyper" problem ... one obvious workaround at the kdenlive level would be to not include that option if there is no rescaling being done, but if that rescaler is introducing jitter, that might be a bug the ffmpeg folks would want to know about too ... or there may be a better option for render time rescaling that kdenlive/mlt could use? -- You are receiving this mail because: You are watching all bug changes.
