Feature request: return of frame-generating Blend for slowing down timelapses

[FMartin]

Hi, first of all, thank you for this wonderful and efficient little tool!

I've started using Avidemux a long time ago (probably over a decade) to compile timelapse videos from photos. Many of these are astrophotography, shooting stars or northern lights timelapses, shot in conditions so dim that I have to take longer exposures than I'd like - the solution was to use the Change FPS filter's blend option in the old versions, so it would generate an intermediate frame between real frames, and I could have a 30 fps video from just 15 frames - double the duration, not as hectic movement in the skies.

However, this feature was removed in later versions. There is now a separate filter called Blend, but it only combines existing frames to speed up a timelapse - I need the opposite.
I've tried using the Change FPS, from 60 to 30 (like I did many years ago, when the Blend was still there), but that now just results in making the 30 fps project a 15.0x (randomly 15.01 or 15.02 or 15.04 etc) fps file. Here's one of the videos on Yt - since it's slow movement, it's not so apparent that it's just 15 fps, but if you click stats for nerds, you'll see it.

As a workaround, I've also tried combining it with the Resample FPS filter as that still has the Blend option:
Project of 30 fps -> Resample FPS to 60 with Blend enabled -> Change FPS 60 to 30 fps: and the end result is 30.0x fps (again randomly 30.01 or 30.02 or something similar).
Now this workaround works, but it's not very elegant - it would be nice if the slowing-down Blend could be added back. Or is there a better way to do this?

And these random fps numbers, I wish the set fps was better enforced. These are short clips (10-30s), maybe there's not enough granularity, but still. When I found out I'm only getting 15 fps, I resorted to DaVinci Resolve, and it could make it a clean 30.00 fps (however, Resolve is just overkill for this task, way too complicated, resource-hungry and wasteful, I don't like using it). It's kinda close enough, but before I start recompiling a few dozen timelapses, I thought I'd ask Should I open a separate topic for the fps issue?

Thanks!

[sark]

If you are always working with 30fps input, you can create a custom script to instantly apply both filters (and the configuration settings), and apply from the Custom menu with a single click.
No scripting skills are required. If this is of interest I will happily post a simple "how to".

Not sure about your odd framerates, 30.02 and 30.02 etc. Possibly an input with "variable" framerate? Just a guess.

[FMartin]

Thanks for the reply! I've already been using custom presets for some time
With Resample (+blend) and Change fps I can get what I need but the framerate is still an issue, and a bigger one. Maybe I should open a new topic for it?...

The input is jpg files.

I've also tried just turning jpgs into a timelapse, without any Resample and Change fps speed-up or slow-down, and even this way the resulting framerate was 30.28 fps...

[sark]

I cannot reproduce the issue. If I import a group of images they default to 25fps. I can use "Change fps" to adjust to 30fps. Alternatively, I can use "Change fps" to 12.5fps with "Resample fps" set to 30fps and Blend enabled. In both cases output is exactly as set.

I would suggest you do indeed open a new topic, with a precise example of the workflow that is causing the issue.... Good luck.

[FMartin]

Thanks for the reply and thanks for taking the time to try to replicate!
Yes, the default is 25 fps - I think I changed it in Edit / Preferences / Import - Assign following standard frame rate: 30.
I will open a new thread then.