Filter "Speed: Forward only" seems to not consider changed Duration of Clips

[snowmen]

What is your operating system?
Windows 11

What is your Shotcut version (see Help > About Shotcut)?
23.07.29

Can you repeat the problem? If so, what are the steps?
It is about the filter “Speed: Forward only”

I use it in an playlist project to either slow down…

or speed up…

some clips.

• In case of slow down the clip is cut off earlier then it should be,
• in case of speed up, the clip is at the end and then a gap exists in the project until the next clip starts.

It seems, that the changed duration of a clip resulting by slowing down/speeding up is not considered by Shotcut.

[shotcut]

This is currently by design with no plans to change it. Filters are not able to change the playlist, timeline, or clip properties.

[snowmen]

You will have your reasons to think like that, but as a user I cannot follow. Whenever I use a speed changing filter, it will have an effect on the duration of that clip.

So how is the filter supposed to be used?

[shotcut]

The workaround is to adjust the clip duration by trimming (out point) and using Properties > Duration if needed to extend the maximum for the out point.

[brian]

@snowmen

You will have your reasons to think like that

The “reason” is only that it is a lot of work and nobody has volunteered their time for free to make it work they way you expect.

@snowmen

So how is the filter supposed to be used?

This is the advice I have offered in the past. Yes, it is different than other tools. But I do not think it is too cumbersome.

Speed filter and clip length

Go to the clip properties and set the duration to something longer that will meet your needs. Maybe just make it way longer than you need. For example, if you are just going to double the speed, then reduce the length by half. But if you are going to use keyframes to make some interesting effects, maybe you don’t know how long it will need to be until you are done. Apply the Speed filter and adjust the keyframes to your liking Drag the right edge of the clip to trim it back down to the length …

[snowmen]

@brian

The “reason” is only that it is a lot of work and nobody has volunteered their time for free to make it work they way you expect.

Totally fine. No offense intended.

@shotcut

The workaround is to adjust the clip duration by trimming (out point) and using Properties > Duration if needed to extend the maximum for the out point.

Yes, that works for both use cases. It’s just not directly intuitive to use it this way.

Thank you both.

[Kaje68]

Continuing the discussion from Filter "Speed: Forward only" seems to not consider changed Duration of Clips:

Hi, I came here to ask the same question as OP. I was wondering if you could expand on your workaround as I am a bit confused. After I trim it my video is timeline is about a minute. After 5 seconds, I want to accelerate over 5 seconds to 10x. Stay there for like 20 seconds, then decelerate over 5 seconds back to 1x. As soon as I increase speed the video gets compressed while playing but not on the timeline so every time I create a keyframe and adjust the speed it will shift any other keyframe. I don’t understand how changing the duration fixes that? Also, when I go to properties the duration is listed as the value of the untrimmed video.

[brian]

@Kaje68

As soon as I increase speed the video gets compressed while playing but not on the timeline so every time I create a keyframe and adjust the speed it will shift any other keyframe.

My advice is to work from left to right. Adjusting a keyframe only affects the frames for future keyframes. So if you work from left to right, there are no “future” keyframes yet. When you are all done, and like the effect, then make one final trim to the clip to cut off any extra duration at the end.

@Kaje68

Also, when I go to properties the duration is listed as the value of the untrimmed video.

Initially, yes. But you can change it to make it longer. Making it longer is only necessary if you are slowing the speed. If you are only making the speed faster, then, eventually, you will need to shorten the video.

[Grobe]

Hi.

versjon: 24.11.17 - W11.

I used this filter first time a couple of days ago - to make some parts of a long video to play slightly faster. As a relatively fresh user of Shotcut, this went sideways for me because:

• Fail to notice the tendency of the end of a filtered section to repeat. Not until quite into the hour long project did I found something was wrong about the video. Because this is a screen copy (software learning video) - the repeats wasn’t easy to spot until I heard the sound (very basic quality control).
• After I did found irregularity in the resulting playback, I wasn’t able to understand or figure the cause. After some repeat I did come to the conclusion that the timeline was unchanged - interpreted that as a bug, until I found this post.

This issue was mainly because of me not being an advanced user of Shotcut, but If there are no plans for future versions to introduce change of duration for whatever reasons - maybe I can propose some suggestions that reduce the risk of new users (like me) get to produce a video containing unwanted repeats:

• Idea1 - When filters manipulating time are being used the first time after Shotcut install, the user should get a notification to get aware of this limitation.
• Idea2 - I do struggle pin point the correct time to set the marker for split and deleting a section in such a way that it gives a seamless result. Therefore, please introduce an option or script that calculate updated times, and can automatically split away the part that repeats when filter settings make duration shorter.