Its now March, 2025 and Ive found myself in the exact same situation. I have two samples that are both HEVC with audio, and oddly enough they start each Iframe with 00 00 01 FC , subsequent frames indicated by 00 00 01 FD, and audio frames with 00 00 01 FA.

Ffmpeg, VLC, MediaInfo, and myself - all hate these files. Ive got some code set up thats properly extracting each frame by type, but when running tests the single first Iframe, I see only a slim bar at the top of the image containing scrambled video data. The rest of the image is just green..

After much trial and error, Ive noticed that i can remove certain bytes from the header and get more scrambled video data to replace the green, but still no luck on a solid image. Similarly, my first thought was to remove the proprietary 00 00 01 FC bytes, but that usually results in a worse output.

1. What was the "dodgy site" you used?
2. So your first frame should include the 00 00 01 FC but the subsequent frames should not?
3. My file extension is ".dcr", but I do not have access to the camera, the dvr, or anything other than the file itself.
For anyone still reading, here's a chunk of the top of my file. This is the Iframe header im looking at.

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