Codeffmpeg[0x2a3c318]: Stream #0:0: Video: h264 (High 10), yuv420p10le(tv, bt709, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc
There is no broadcast standard for 10-bit H264 (yuv420p10le) media so almost nothing supports hardware decoding of that format, including RPi4. The file will be software decoded by ffmpeg and that might be a challenge. Traditionally Animé fans have used higher spec Intel kit for their collections; there is still zero hardware decode support on the GPU but the CPU has more grunt for the task. I'd suggest experimenting with transcoding 10-bit H264 files to HEVC. The transcode will be slow, but it's a one-time task and can be scripted easily.
Seems like watching h265 10-bit will be a better idea then, thanks!