SUMMARY

Hi.

The latest version of Kdenlive (25.08.1, flatpak) cannot decode most h.264 and VP9 files on my system (Fedora Sliverblue 42).

When the clip is shown in the clip monitor, the audio playback functions correctly, but the video just shows a "transparency checkerboard" and shows these errors when launched via commandline:

h.264 file:
[libopenh264 @ 0x563bfdfa1300] [OpenH264] this = 0x0x563c011db500, Error:DecodeCurrentAccessUnit()::::::PrefetchPic ERROR, pSps->iNumRefFrames:4.
[libopenh264 @ 0x563bfdfa1300] DecodeFrame failed

VP9 file:
[opus @ 0x7f227c036e40] Could not update timestamps for discarded samples.
[opus @ 0x7f227c034840] Error parsing Opus packet header.

If the clip is placed on the timeline and the playhead is over it, the project monitor shows a black screen.

Downgrading via the command below fixes the issue (Kdenlive still says it's at version 25.08.1 in the about menu for some reason?)
'run0 flatpak update --commit=9f28077f3e213194be22abf099c44bd21d1c8f57c3b296ba8583690a333dd629 org.kde.kdenlive'


STEPS TO REPRODUCE
1. Drop an mp4 in the project bin
2. Click on it

OBSERVED RESULT
The clip monitor can play audio, but shows a "transparency checkerboard" instead of the video.

EXPECTED RESULT
The clip monitor can play the video correctly.

SOFTWARE/OS VERSIONS
Linux: Fedora Silverblue 42.20251005.0
Kdenlive: 25.08.1 (flatpak)
CPU: AMD Ryzen™ 5 9600X × 12
GPU: AMD Radeon™ RX 7600