Very simple bug - set your video codec to x264, open "Configure", change the 'threads' amount to something other than "Auto" and click OK. Then open "Configure" again and observe that the 'thread' settings is now set to one value less.
This bug exists on both Linux and Windows, but the nightly Linux builds don't want to launch on the various live Linux ISO distros I tested with (Xubuntu, openSUSE tumbleweed Xfce, Linux Mint Xfce).
Video demonstration using the live ISO of Hiren's BootCD PE (https://www.hirensbootcd.org/) for easy reproduction:
- https://archive.org/details/avidemux-nightly-2025-05-26_x264-threads-setting-gets-set-one-value-less-each-time-you-view-configure (https://archive.org/details/avidemux-nightly-2025-05-26_x264-threads-setting-gets-set-one-value-less-each-time-you-view-configure)
Now admittedly this bug has been around since at least the stable release of Avidemux 2.8.1 but I didn't report it at the time since I was a bit late to updating from the previous version, and therefore I figured "the next version should be out soon anyway and I'll double-check it then".
...it's now like 3 years later and v2.8.1 is still the newest stable release, but I realized that the website's downloads page has a link to nightly builds that I was able to subsequently use to test and confirm that, yes, this bug still exists (DISCLAIMER: being a Linux user, I'm used to downloading Avidemux via my distro's software manager which includes flatpaks like Avidemux - I haven't had to go to Avidemux's "downloads" page since my Windows 7 days.
Should be fixed by x264/qt: fix threads combo box index off-by-one on upload to configuration dialog (https://github.com/mean00/avidemux2/commit/85b0ac089ef5b5f460c5bbef50be69ef74234bb0), thank you for your report.