Hi!

I'm often working with big amounts of spoken video material (like 1h-2h). I think that I could be more effective with editing, if I could change the playback speed.

How I imagine it could work is I'd have a "playback speed" silder somewhere near the timeline preview window That I could set from 100% to (say) 500% with precision.
I'd also like to have a toggle switch so I can quickly switch between sped up and regular speed playback, also with a hotkey.

I know Kdenlive has a "Speed" effect. There are two problems with it:

1. It will affect the pitch of the audio, so fast playback will inevitable make the speech unrecognizable very quickly.
2. It is not possible to use it temporarily to only speed up preview playback, but have the rendered video play at normal speed.

I am using Proxy footage anyway for editing, and even on a machine with a Ryzen 7 1700 CPU, still compositing frames seems to be the biggest bottleneck. Even with proxy in place I usually have no more than 12 FPS playback if I composite anything. So I mostly just disable a bunch of tracks and edit using the audio waveforms, audio cues from the recorded speech and a part of the captured video proxy.

I am not sure if adding a sped-up playback overhead on top of that would serve me any better (it would not, unless I can get at lest 30 FPS of regular playback anyway).

VLC seems to handle playback changes pretty well with time stretching in place, so the audio pitch is not affected - I don't know if they use librubberband or what.

I guess fast playback of non-proxied video streams could be tricky, and add a big overhead since the inter-frames need to be processed way faster - or if you just skip between keyframes it should be faster and require less disk IO, but the playback will be very choppy. For proxy footage I guess it should not be a problem since all frames are encoded independently (for fast scrubbing).

What do you think of that?

PS: I've just learned that Kdenlive does support faster playback with JKL keys.

The problem is that the audio gets all choppy and I can't understand the speech while using it.
Also maybe if the speed-up steps were smaller that wouldn't be such a big deal?

It sounds like the audio stream is hard-cut to play only every Nth block. With some crossfading between these blocks I guess the sped-up playback audio quality should be greatly improved. I have no idea how to implement that however.

I know this is an old topic but I found it searching for a way to use fast playback in Kdenlive. I also use JKL keys and audio gets really choppy even at 1.1 speed. I'm using Kdenlive 20.08.3. Is there any workaround? Faster playback while editing would be really great.

I would like to upvote this one. I am running kdenlive 20.08.02 appimage on Kubuntu 20.04.1 LTS, and I have the choppy sound too.

I also would like to playback a video at increased speed (around 1.5x) without choppy sound. I have many videos to review, to isolate specific clips, and it could be very useful if I could play them faster in the clip monitor while it's still intelligible (even if it's a chipmunk voice, I don't care).

Hi again.

While investigating how the scrubbing audio is working and try to change it, I've noticed something abnormal : when forwarding the speed is multiplied by ten instead of x1.5 (no problem for rewinding).

I think this difference is coming from the MLT library, because the speed array in kdenlive's code is the same for rewinding and forwarding. Same thing for the scrubbing audio, it's seems fully managed by MLT.

Is there some way to workaround this ? I tried changing the speed for something quite slower but no other value is working...

I have the same problems and more with this functionality.

Problem 1: Pressing "l" once sets the speed to 1.5x but it doesn't actually play back faster. Pressing "l" again then sets it to 2.0x and then it does actually play back faster.

Problem 2: I can't select a speed like 1.25, 1.5 or 1.75, commonly used for faster viewing, where it's still possible to listen to audio, to quickly check clips/videos.

The first looks like a bug, and the second one could easily be added by making the intervals different (e.g. 1->1.25->1.5->1.75->2->2.5->3->4->5...) or by just allowing the user to *click* on the "1.5x" that appears in the monitor window, and allow to put a custom value there or selection from a drop-down.

Also it would be really useful if that "1.5x" label was there always and just display "1.0x" when it's playing at normal speed, so a user knows that this functionality is there and can click on it and a dropdown appears to change the speed. That way, a user wouldn't have to google and find out about magic JKL keys.

I know it is an old thread, but this feature is the only one I miss and refrains me from using kdenlive. There doesn't seem to be any improvements with the latest version (21.08.1)
2x sound is choppy and cracks very unpleasantly.
Are there any news about this ? I couldn't find any after 40 minutes of research...

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