Created attachment 184633 [details]
Screenshot of the "Unknown Error" popup

SUMMARY
When I try to render an animation, I get an "Unknown Error" popup.

STEPS TO REPRODUCE
1. Make a new file
2. Make an animation with the timeline docker
3. File -> Render Animation
4. Click OK

OBSERVED RESULT
After the program saves the frames, an error popup shows up saying "Could not render animation: Unknown error."
The error log left where the render export path was set says:
> D:/Krita (x64)/bin/ffmpeg.exe -hide_banner -y -y -r 12 -start_number 0 -start_number_range 1 -i D:/Mis Cosas/Imagenes/Por mí/frame%04d.png -c:v libopenh264 -b:v 5000k D:/Mis Cosas/Imagenes/Por mí/animation_bug_test_sep2025.mkv
> =====================================================
> [image2 @ 000002c2b92eefc0] Could find no file with path 'D:/Mis Cosas/Imagenes/Por mí/frame%04d.png' and index in the range 0-0
> [in#0 @ 000002c2b92e5e00] Error opening input: No such file or directory
> Error opening input file D:/Mis Cosas/Imagenes/Por mí/frame%04d.png.
> Error opening input files: No such file or directory
I made a minimal reproduction project but, oddly, when I moved it to desktop and rendered there, it worked just fine.
> D:/Krita (x64)/bin/ffmpeg.exe -hide_banner -y -y -r 24 -start_number 0 -start_number_range 1 -i C:/Users/2020/Desktop/Krita animations/frame%04d.png -c:v libopenh264 -b:v 5000k C:/Users/2020/Desktop/Krita animations/animation_bug_test_sep2025.mkv
> =====================================================
> Input #0, image2, from 'C:/Users/2020/Desktop/Krita animations/frame%04d.png':
>   Duration: 00:00:01.00, start: 0.000000, bitrate: N/A
>   Stream #0:0: Video: png, rgba(pc, gbr/unknown/unknown), 1920x1080 [SAR 2834:2834 DAR 16:9], 25 fps, 25 tbr, 25 tbn
> Stream mapping:
>   Stream #0:0 -> #0:0 (png (native) -> h264 (libopenh264))
> Press [q] to stop, [?] for help
> [libopenh264 @ 000001d12a8f2a00] [OpenH264] this = 0x000001D12A825BC0, Warning:layerId(0) doesn't support profile(578), change to UNSPECIFIC profile
> [libopenh264 @ 000001d12a8f2a00] [OpenH264] this = 0x000001D12A825BC0, Warning:bEnableFrameSkip = 0,bitrate can't be controlled for RC_QUALITY_MODE,RC_BITRATE_MODE and RC_TIMESTAMP_MODE without enabling skip frame.
> Output #0, matroska, to 'C:/Users/2020/Desktop/Krita animations/animation_bug_test_sep2025.mkv':
>   Metadata:
>     encoder         : Lavf61.7.100
>   Stream #0:0: Video: h264 (H264 / 0x34363248), yuv420p(tv, progressive), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 5000 kb/s, 24 fps, 1k tbn
>       Metadata:
>         encoder         : Lavc61.19.101 libopenh264
>       Side data:
>         cpb: bitrate max/min/avg: 5000000/0/5000000 buffer size: 0 vbv_delay: N/A
> frame=    5 fps=0.0 q=-0.0 size=       1KiB time=00:00:00.16 bitrate=  27.7kbits/s speed=0.333x    
> frame=   24 fps= 24 q=-0.0 size=       1KiB time=00:00:01.00 bitrate=   4.6kbits/s speed=0.983x    
> [out#0/matroska @ 000001d12a828100] video:424KiB audio:0KiB subtitle:0KiB other streams:0KiB global headers:0KiB muxing overhead: 0.187688%
> frame=   25 fps= 24 q=-0.0 Lsize=     425KiB time=00:00:01.04 bitrate=3341.2kbits/s speed=1.01x    
I tried the same with the animation I was trying to render, but instead I got the error again.
I also tried rendering the MRP in a location that wasn't the same as the .kra file's, and I got the error as well.

EXPECTED RESULT
The animation renders without a hitch, regardless of location.

SOFTWARE/OS VERSIONS
Windows 10 Version 2009
Qt Version: 5.15.7

ADDITIONAL INFORMATION
I've had this issue before (https://bugs.kde.org/show_bug.cgi?id=474679) and the assignee had successfully fixed it. Would this be a regression?