Recommendation on procedure to add audio track not synchronized with the video

Hello:
I was disconnected from video editing and the forum for a long time, as well as from the new features and functionalities that have been implemented.

I have two videos:
First video with low resolution and quality, but with an audio track dubbed in Spanish.
Second video with good quality and audio in English only.
Both video sources are not synchronized, so the timings do not match.

My procedure is to edit the audio (stretching and shrinking as needed) taking the waveforms from both videos as a reference. I do this (when it comes up) in a DAW software trying to preserve the tone.
However, for these two video sources, in the audio waveforms I do not have clear references to use my procedure.
Normally the soundtrack and the music behind the voices have always helped me adjust the timing, but this is not the current case, where even the music is different between versions.
Then perhaps I can adjust the video speed (time remap filter), to match the frames, as I can visually compare specific frames and their respective timestamps.
Speed ​​variations are minimal between versions, but affect the synchronization between the video and the new audio track.
From this, I can experiment and check.
When the Time remap filter was implemented in Shotcut a long time ago, I didn’t know how to use it.
That’s why I remembered that perhaps this functionality, unexplored by me, could be an option to solve my problem.
Is there any idea on how I could implement this? Is my idea feasible?
In short:
Is there a quick procedure to do this manually? or even better, is there any automatic or semi-automatic procedure to do this in Shotcut?
Thanks for reading me. :slightly_smiling_face:

Hi @ejmillan, and welcome back!

If we don’t take into account the quality and the audio tracks, do I understand that both videos are identical, except that one plays slightly faster than the other one?

Instead of the Time Remap filter, you could use Speed in the Properties panel to speed up the slower clip until it matches the faster one.
cnj2UXrria

Example:

  • Faster clip on track V1
  • Slower clip on track V2
  • Select the clip on track V2 and go to the Properties panel.
  • Increase the Speed to 1.010000 and click on the Apply button.
  • Move the playhead near the end of the clips and visually compare the frames of both clips.
  • If the clip on V2 is still too slow, increase the Speed again by a small value.
  • Repeat until both clips are synchronized.
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Hello Musicalbox. Here I am again.
Thanks for your answer.

The problem with this is that there are different speed variations throughout the video. Some parts are faster and others are slower.
Furthermore, the inclusion of the headers and title transitions in the more modern and remastered version ended up ruining the consistency of the speed.
If the videos were identical, I could use the speed change to the entire video, but that is not the case at hand.
I have already tried the solution you give me, but it didn’t work completely.
I used that speed adjustment method, and it worked but only for the opening video cut, for the rest of the video, there doesn’t seem to be an easy solution.

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After some checking, I found that the videos are not the same. In the transitions between scenes, one of the videos has crossfade, while the remastered one makes a direct transition without crossfade.
So I’m doing an edit comparing both video sources on the monitor (side by side using the size and position filter).
I do an approximation by changing the speed of the clip and when it starts to desynchronize again, I cut and adjust the speed again for the new clip.
Here in the screenshot, in track V2 you can see the first clip with speed set to x 0.9548 and the second clip at x 0.96,
It’s a laborious process, but it works.

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