Bug 455504

Summary: When i change the clip's speed, the clip has its start/end fowarded by one frame
Product: [Applications] kdenlive Reporter: Fernando M. Muniz <fernandommuniz>
Component: Video Effects & TransitionsAssignee: Jean-Baptiste Mardelle <jb>
Status: CONFIRMED ---    
Severity: normal CC: erjiang, fritzibaby
Priority: NOR    
Version First Reported In: 24.08.2   
Target Milestone: ---   
Platform: Flatpak   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: How to find the glitch
Video clip showing frame number

Description Fernando M. Muniz 2022-06-17 18:21:03 UTC 
SUMMARY
When i change the clip's speed, the clip has its start/end fowarded by one frame

STEPS TO REPRODUCE
1. Alter the speed of a trimmed clip.

OBSERVED RESULT
The clip has its start/end fowarded by one frame, which means that the clip begins one frame before where it was supposed to start, and ends one frame before it was supposed to end. The issue becomes very apparent when for ex; You are taking one scene from a movie, then you look at the first frame do your rendered video and it's from the previous scene.

EXPECTED RESULT
The speed of the clip being altered without being fowarded by one frame.

SOFTWARE/OS VERSIONS
Windows: 11


ADDITIONAL INFORMATION
1. When i change the clip's speed (in my case i choose 50% speed), the clip has its start/end fowarded by one frame, which means that the clip begins one frame before where it was supposed to start, and ends one frame before it was supposed to end. The issue becomes very apparent when for ex; You are taking one scene from a movie, then you look at the first frame do your rendered video and it's from the previous scene.

2. When using "reverse clip" after adjusting the frames at the beginning and at the end of the already slowed down clip, the clip isn't affected. However, if the clip had no prior edits, and then i apply "reverse clip" at 100%, the clip has its start/end fowarded by one frame, just like i've described in the first situation.
When applying "reverse clip" at 50%, instead of being one frame at the beginning and end, now there are two on each.

In both cases, it involves a video that got trimmed down into a scene with the razor tool. I don't think the glitch happens when using a video for these speed edits, since unlike trimmed clips, there's no frames beyond the start and end of it.
Comment 1 Fernando M. Muniz 2022-06-20 11:21:48 UTC 
Created attachment 149949 [details]
How to find the glitch

How to find the glitch, the same applies with slowing down the clip's speed.
Comment 2 erjiang 2022-07-02 04:21:45 UTC 
Created attachment 150332 [details]
Video clip showing frame number

Something is definitely not quite right here. I tried this out with a frame counter video clip (attached) and changing the speed to 50% caused the end frame to end later than expected (start frame seemed correct though).
Comment 3 erjiang 2022-07-02 04:46:20 UTC 
Maybe someone else can weigh in? If I have a clip with 20 frames, the slow it down to 50% speed, the current behavior is:

* frame 1 appears for 1 frame,
* frames 2-19 appear for 2 frames each
* frame 20 appears for 3 frames

If the full clip is longer than 20 frames, then instead of frame 20 appearing for 3 frames, frame 20 appears for 2 frames and frame 21 appears for 1 frame.

It seems like the slowed-down clip is starting 0.5 frames too late, and instead each frame of the video should appear for 2 frames each.
Comment 4 Fernando M. Muniz 2023-06-25 13:21:44 UTC 
The glitch is still there.
Comment 5 Fernando M. Muniz 2024-09-19 16:35:04 UTC 
*** Bug 424582 has been marked as a duplicate of this bug. ***