Audio/ Video tracks in timeline go out of sync after export

Help/How To
1

Hi, I’ve spend hours trying to understand root of sync problem I’m experiencing with current project and I’m aware that there are forum topic partially covering this issue.

I have decided to create new topic as all previous seems to refer to audio from video track where in my case its sync between video and audio tracks within timeline.

I’m working on “manual multi cam editing” and I have perfectly aligned video with audio track in Shotcut.
Only after video is exported audio sync is lost. Video is only 3 min ish long but sync problems are visible from start of rendered mp4.

I have extracted audio and video only using ffmpeg as per other posts (Audio Aligns With Video In Shotcut, But Goes Out Of Sync After Export)

and video file is slightly shorter then audio file.

Frame rate is 25 on all videos used for final edit track and everything looks ok within Shotcut.
Audio track uses .wav file (no video) / Video track Audio is muted.

Video track consists many clips from different cams ( previously sliced and arranged on one track)

What Am I doing wrong? Is it codec issue or some sort of bug? Is video loosing frames or smth?
I know there was MLT bug in past but did think its fixed now:

Please advise, thanks

2

I forgot to mention I have tried to export with parallel processing turned off and still experienced same sync issue.
Interestingly my previous project seems to retain sync but it only had 3 cams and not so many sliced views. Current project have 7 cams which change quite frequently (sliced in many places). Could slicing cause frame dropping and as a result reduce final video length / out of sync effect?

3

Problem solved!, it was GPU Processing causing out of sync issues … I think its visual rather then actual exporting/rendering…

Anyway everything syncs ok in normal mode.

4

Hi. Can you expand on what you mean by the GPU was causing the issue? I am having the same issue.

5

It was “GPU Processing” selected within Shotcut Settings… which in my case was causing sync issues.

6

Oh. I don’t even have that option. I was hoping turning that on was what fixed your issue.

7

I have this syncing issue. Separate video and audio tracks, from separate sources, aligning perfectly in Shotcut project, but out of sync after export.
Using 14 video clips in 30s video - could this be the issue? Frame rate is 29, video file is .mov, audio file is .mp3.
Start of each clip is aligned to a beat in the music in Shotcut timeline. Export starts ok, but out of time for last few clips. Does anyone know a way round this?

8

I have saved the audio as .WAV rather than .MP3 and this has solved my lag issue.

9

did you ever sort it I have this problem ahhhhh!!! I’m playing and singing using audio from another source. I join the spikes up and its syncs fine in edit but when I export it plays slightly out of sync… I am maybe going to try another editing package if I can’t sort this… please help

regards phil

10

Hi Phil,
Yes I did manage to sort it - by using .WAV files rather than the .MP3 I used initially. This has resolved the issue for me. I hope it does for you too!