Bug 438483

Summary:	proxy clips and non proxy clips sometimes differ by a frame
Product:	[Applications] kdenlive	Reporter:	wkgolhfj
Component:	Rendering & Export	Assignee:	Jean-Baptiste Mardelle <jb>
Status:	REPORTED ---
Severity:	major	Keywords:	triaged
Priority:	NOR
Version First Reported In:	21.04.1
Target Milestone:	---
Platform:	Fedora RPMs
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description wkgolhfj 2021-06-11 23:38:56 UTC

proxy clips and non proxy clips sometimes differ by a frame


STEPS TO REPRODUCE
1. create new project and import clip with 29.97fps
2. press "switch" to change to clip profile 29.98fps ([resolution] 29fps)  [is this the cause?]
3. right click clip and turn on proxy clip
4. drag clip into timeline
5. make some cuts
6. right click original clip in project bin and turn off proxy clip

OBSERVED RESULT
some cuts are now one frame off. the cuts are one frame too late in my experience.
it's not the cut position in the timeline that changes, but the cut position in the clip. let's say i want to cut away one frame before the big explosion happens. this bug sometimes causes the first frame of the explosion to render in the final video if i don't render using proxy clips.


EXPECTED RESULT
proxy clips and non proxy clips should have all cuts on the same frame

SOFTWARE/OS VERSIONS
Linux: 5.12.9-300.fc34.x86_64 

ADDITIONAL INFORMATION
ffmpeg Version: 4.4

Comment 1 wkgolhfj 2021-06-11 23:58:15 UTC

my original clip has these properties:

Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, smpte170m/smpte170m/bt709), 1920x1080, 15064 kb/s, 29.98 fps, 29.97 tbr, 90k tbn, 180k tbc (default)



the proxy clip kdenlive created has these:

Stream #0:0: Video: mjpeg (Baseline), yuvj420p(pc, bt470bg/unknown/unknown), 640x360, 29.97 fps, 29.97 tbr, 1k tbn, 1k tbc (default)