Time stretching doesn't work on VSE strips #118296

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opened 2024-02-14 22:24:54 +01:00 by Eliot-Alan-Foss · 7 comments

Eliot-Alan-Foss commented

2024-02-14 22:24:54 +01:00

System Information
Operating system: Linux-6.1.0-17-amd64-x86_64-with-glibc2.36 64 Bits, X11 UI
Graphics card: Quadro RTX 3000/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 470.161.03

Blender Version
Broken: version: 4.0.2, branch: blender-v4.0-release, commit date: 2023-12-05 07:41, hash: 9be62e85b727
Worked: Unknown

Short description of error
Time stretching on strips in the VSE not working properly. Does seem to work on keyframes/animations tied to keyframes.

Exact steps for others to reproduce the error
Start a video editing project
Import some video file
confirm playback works at normal speed
edit time stretching in output property tab (under frame range) (ex: old: 100 new: 200)
Refresh video sequencer (ctrl e)
playback video
preview shows normal speed video
Rendered animation also shows normal video speed.

**System Information** Operating system: Linux-6.1.0-17-amd64-x86_64-with-glibc2.36 64 Bits, X11 UI Graphics card: Quadro RTX 3000/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 470.161.03 **Blender Version** Broken: version: 4.0.2, branch: blender-v4.0-release, commit date: 2023-12-05 07:41, hash: `9be62e85b727` Worked: Unknown **Short description of error** Time stretching on strips in the VSE not working properly. Does seem to work on keyframes/animations tied to keyframes. **Exact steps for others to reproduce the error** Start a video editing project Import some video file confirm playback works at normal speed edit time stretching in output property tab (under frame range) (ex: old: 100 new: 200) Refresh video sequencer (ctrl e) playback video preview shows normal speed video Rendered animation also shows normal video speed.

Eliot-Alan-Foss added the

labels 2024-02-14 22:24:55 +01:00

Pratik Borhade commented

2024-02-15 07:06:20 +01:00

Member

Hi, thanks for the report. Can confirm. Think this can be achieved in VSE with speed factor or retiming keys.
Not sure if time stretching is expected to work with strips. cc @iss

Hi, thanks for the report. Can confirm. Think this can be achieved in VSE with speed factor or retiming keys. Not sure if time stretching is expected to work with strips. cc @iss

Pratik Borhade added

Needs Info from Developers

Video Sequencer

and removed

labels 2024-02-15 07:06:33 +01:00

Eliot-Alan-Foss commented

2024-02-15 20:02:23 +01:00

Author

Yes, have used retiming of strips successfully (although I have run into weird/buggy behavior with them).

I use keyframes in the VSE to animate properties of the videos. (for instance, I have a picture/text overlayed onto the video which I want to scroll across the video, so I use keyframes of the transform properties for these strips). If I use the time stretching, the keyframes follow the stretched time, but the video doesn't.

This may be due to some inherent limitation, but it does feel unintuitive that stretch time affects some portions of the project (keyframe timing/graph editor) while leaving other part untouched (Video Sequencer).

Yes, have used retiming of strips successfully (although I have run into weird/buggy behavior with them). I use keyframes in the VSE to animate properties of the videos. (for instance, I have a picture/text overlayed onto the video which I want to scroll across the video, so I use keyframes of the transform properties for these strips). If I use the time stretching, the keyframes follow the stretched time, but the video doesn't. This may be due to some inherent limitation, but it does feel unintuitive that stretch time affects some portions of the project (keyframe timing/graph editor) while leaving other part untouched (Video Sequencer).

Richard Antalik commented

2024-02-15 20:18:45 +01:00

Member

This was never supported, but it's not complicated to support this use case now. Still it's a known issue, though undocumented.

This was never supported, but it's not complicated to support this use case now. Still it's a known issue, though undocumented.

Richard Antalik added

and removed

Needs Info from Developers

labels 2024-02-15 20:19:06 +01:00

Richard Antalik commented

2024-02-15 20:51:03 +01:00

Member

Well actually not quite easily... The main issue is, how sound strip layout is presented to audaspace + its playback speed is normal.
So a best solution would be to implement time remapping in audaspace, which is not one-line fix.

Well actually not quite easily... The main issue is, how sound strip layout is presented to audaspace + its playback speed is normal. So a best solution would be to implement time remapping in audaspace, which is not one-line fix.

Eliot-Alan-Foss commented

2024-02-16 00:27:06 +01:00

Author

I wanted to do this because while editing video, sometimes I am trying to line something in the sequencer with some audio event.

For example, I want to have text that shows up right when someone start speaking. (I could do this by looking at the audio waveform, but that won't work every time). It can be annoying to have to stop the playback right on the correct frame to determine which frame is the desired one. (ie, there is no way to "scrub" the audio to find the desired frame).

Therefore, I felt that if I could perform playback in "slow motion" it would be easier to mark audio events. I know setting the speed of the strip works, but it changes the timing. I want an option that can allow me to slow down playback of audio without messing up the timing of the strips, so I can map key moments in the audio to a frame in the project.

I thought that time stretching might do what I was looking for (more of a global slow motion), but it didn't work. Changing the frame rate of the project rescales strips in the sequencer, but I am effectively looking for a way to change the "frame rate" of the preview, such that the audio is slower and one can be more precise in finding the closest frame to an audio event.

I guess blender uses frames as the basis of many parts of the software, but since "frames" of audio files are much more closely spaced, it can be hard to work with both at the same time.

I wanted to do this because while editing video, sometimes I am trying to line something in the sequencer with some audio event. For example, I want to have text that shows up right when someone start speaking. (I could do this by looking at the audio waveform, but that won't work every time). It can be annoying to have to stop the playback right on the correct frame to determine which frame is the desired one. (ie, there is no way to "scrub" the audio to find the desired frame). Therefore, I felt that if I could perform playback in "slow motion" it would be easier to mark audio events. I know setting the speed of the strip works, but it changes the timing. I want an option that can allow me to slow down playback of audio without messing up the timing of the strips, so I can map key moments in the audio to a frame in the project. I thought that time stretching might do what I was looking for (more of a global slow motion), but it didn't work. Changing the frame rate of the project rescales strips in the sequencer, but I am effectively looking for a way to change the "frame rate" of the preview, such that the audio is slower and one can be more precise in finding the closest frame to an audio event. I guess blender uses frames as the basis of many parts of the software, but since "frames" of audio files are much more closely spaced, it can be hard to work with both at the same time.

Richard Antalik commented

2024-02-16 18:14:47 +01:00

Member

There is audio scrubbing though you can enable it in playback popover https://docs.blender.org/manual/en/4.1/editors/timeline.html?utm_source=blender-4.1.0-beta#bpy-types-scene-sync-mode

There is audio scrubbing though you can enable it in playback popover https://docs.blender.org/manual/en/4.1/editors/timeline.html?utm_source=blender-4.1.0-beta#bpy-types-scene-sync-mode

Eliot-Alan-Foss commented

2024-02-21 22:17:56 +01:00

Author

Thank you. This will work well for me. Thank you for the information. This should work for my use case.

I will still leave the case open, as I do think that it is somewhat unexpected that the time stretching wouldn't affect video and audio strips.

Thank you. This will work well for me. Thank you for the information. This should work for my use case. I will still leave the case open, as I do think that it is somewhat unexpected that the time stretching wouldn't affect video and audio strips.

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