FFmpeg concat demuxer not working: No error, and no output

Question

PROBLEM: 3 identical-format files (all exported in batch together, with identical settings) concatenated using ffmpeg concat demuxer. Command runs without error (and no console printouts either) but also no output file. Mac OS 10.15.6, ffmpeg version 4.3.1

Concat text file "test.txt" as follows:

file 'test_clip1.mp4'
file 'test_clip2.mp4'
file 'test_clip3.mp4'

Each of these files ffprobe readouts are the same. There is no audio stream.

test_clip1.mp4:

Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080, 911 kb/s, 23.98 fps, 23.98 tbr, 19184 tbn, 47.96 tbc (default)

test_clip2.mp4

Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080, 628 kb/s, 23.98 fps, 23.98 tbr, 19184 tbn, 47.96 tbc (default)

test_clip3.mp4

Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080, 615 kb/s, 23.98 fps, 23.98 tbr, 19184 tbn, 47.96 tbc (default)

FFmpeg command:

ffmpeg_cmd = ["ffmpeg",
              "-f",
              "concat",
              "-safe", "0",
              "-i", "test.txt",
              "test_concatenated.mp4"]

@Gyan, thank you! It worked immediately. Turns out this is a real facepalm mistake. I forgot to actually subprocess.call the command itself! — dv151
– dv151, Commented Aug 24, 2020 at 15:13

dv151 · Accepted Answer · 2020-08-24 19:11:59Z

0

Facepalm mistake. I forgot to actually CALL the ffmpeg_cmd in my script with subprocess.call. FF command also worked just fine when called directly from the console. Thank you @Gyan for the tip.

answered Aug 24, 2020 at 19:11

dv151

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