FFMpeg concat demuxer unsafe file name
Either run
ffmpeg.exe -f concat -safe 0 -i
"C:\Users\mtst\Desktop\Clips\keep\keep.txt" -c copy
"C:\Users\mtst\Desktop\Clips\keep\keep.mp4
Or don't use absolute (full) paths in keep.txt
Either run
ffmpeg.exe -f concat -safe 0 -i
"C:\Users\mtst\Desktop\Clips\keep\keep.txt" -c copy
"C:\Users\mtst\Desktop\Clips\keep\keep.mp4
Or don't use absolute (full) paths in keep.txt