ffmpeg -i broken.mp4 -c copy fixed.mp4 If remuxing doesn’t work, re-encode a short segment:
ffmpeg -i broken.mp4 -t 30 -c:v libx264 -c:a aac output.mp4 (replace 30 with true length in seconds)
ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 broken.mp4 If output is huge (e.g., 943800 seconds), the duration metadata is wrong.
Use ffprobe (part of FFmpeg):