Do you have Apple Silicon, and Sony XAVC-S (H.264) 10-bit 4:2:2 by chance?
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macOS 14 Sonoma QuickTime Player does not play video codecs like H.265 with Codec ID hev1, VP8 and VP9, and audio codecs like Opus and Vorbis, and wrappers like .avi, .mkv and .webm.
ffmpeg can losslessly and very fast fix that H.265 with Codec ID hev1 issue with:
ffmpeg -i input.mp4 -c copy -tag:v hvc1 output.mp4
macOS 10.14 Mojave QuickTime Player does not play H.265 with Chroma subsampling 4:2:2 (Bit depth 10 bits).
I have heard that starting with Ventura 13.4 on Apple Silicon, Sony XAVC-S (H.264) 10-bit 4:2:2 material at 100 fps or 120 fps shows black video and no audio in FCP 10.6.5 and Resolve Studio 18.1.4. Pro Video Formats were apparently unchanged for Ventura 13.4, still on version 2.2.4.
A workaround is to use Handbrake to convert the video. ffmpeg can convert that Sony footage to QuickTime compatible ProRes 422 HQ, H.265 or H.264 .mov with:
ffmpeg -i input.mp4 -c:v prores_ks -profile:v 3 -timecode 00:00:00:00 -c:a copy prores422hq.mov
ffmpeg -i input.mp4 -c:v libx265 -crf 28 -preset medium -timecode 00:00:00:00 -tag:v hvc1 -c:a copy h265.mov
ffmpeg -i input.mp4 -c:v libx264 -pix_fmt yuv420p -crf 23 -preset medium -timecode 00:00:00:00 -c:a copy h264.mov
https://discussions.apple.com/thread/254881462?answerId=259185079022#259185079022
https://discussions.apple.com/thread/254860809?answerId=259061426022#259061426022
IINA and VLC should have no issues with playing any decent new or old codec.
Handbrake, Shutter Encoder, VLC and ffmpeg can be used to convert old codecs to H.264 or H.265 video and AAC audio wrapped as common mp4 (or its very close cousin .m4v or .mov. I have used MacPorts to install ffmpeg but there are also precompiled versions).
Avidemux and ffmpeg can be used to losslessly fix some issues with codecs or wrappers.
https://iina.io
https://www.videolan.org
https://handbrake.fr
https://www.shutterencoder.com/
https://avidemux.sourceforge.net
https://ffmpeg.org
https://www.macports.org