Bug: timelapse from jpgs -> slight framerate variations in output

[FMartin]

Hi! Again, thank you for this wonderful and efficient little tool, I've used it for many years to compile timelapses of the night skies or auroras so even those can enjoy who can't travel there or can't tolerate the cold.
 
Lately unfortunately I've noticed a bug: the output framerate is not precise, there is a slight variation, e.g. instead of 30.000 fps, I randomly get 30.01, 30.02, ... even up to 30.28 fps.

I'm using Avidemux 2.8.1 on Windows 10

When I open the first jpg, this is the Info / Properties window:

=====================================================
Video
=====================================================
Codec 4CC:         MJPG
Image Size:         3840 x 2558
Aspect Ratio:         1:1 (1:1)
Frame Rate:         25.000 fps
Average Bitrate:      408672 kbps
Total Duration:         00:00:04.240
Pixel format:         YUV 4:2:2, 8-bit
Color range:         Full (JPEG)
Color primaries:      BT.709
Transfer characteristics:   BT.709
Color space:         BT.470 System B/G

=====================================================

This is just a hundred photos for a quick test, but I've go the same issue even with 6-700 photo timelapses.

My normal process would be to add my saved preset with filters through the Custom tab, that involves a cropping to 16:9, then to get half-speed with blend, first Resample FPS to 60 fps with Blend on, then Change FPS from 60.000 to 30.000; then some Eq2 and Denoise3DHQ - this results in files that are close to 30 fps, but always a fraction over: 30.01, 30.02, .. even up to 30.28 fps.
I've tried it also with the Resample and Change FPS filters, but the issue persists.

I still had the old 2.7.8 installed, unfortunately that doesn't have the Blend option in Resample FPS, and I can't find how to set the project default to 30 fps, but at least there the output is a clean 30.000 fps.

Let me know if you have any ideas what might be causing it.
Thanks!

[sark]

Hi again.

Hopefully eumagga, who currently maintains Avidemux, will be able to help. Firstly though, I strongly recommend you try the latest 2.8.2 (241212) version of Avidemux. 2.8.1 is very old.

https://www.avidemux.org/nightly/win64

[eumagga0x2a]

Firstly though, I strongly recommend you try the latest 2.8.2 (241212) version of Avidemux. 2.8.1 is very old.

Exactly, 2.8.1 is ancient. All reported issues must be verified against latest 2.8.2 developer builds.

My normal process would be to add my saved preset with filters through the Custom tab, that involves a cropping to 16:9, then to get half-speed with blend, first Resample FPS to 60 fps with Blend on, then Change FPS from 60.000 to 30.000

Always add "Resample FPS" after "Change FPS" to the filter chain (a second instance, if necessary).

With this condition follwed, please verify that the issue persists with the latest available 2.8.2 nightly build. The last known good official cross-compiled build, as sark said, is r241212. I didn't have time to test the latest VC++ nightly build from May 9 yet, the previous one was still missing some features and suffered from the upstream Qt installer bug which broke uninstallation via Windows Settings (to uninstall it, run the uninstaller in the program directory).