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I have a problem with video mp4 concatenation using ffmpeg. I have two the same videos and I want to concatenate them. I created file inputs.txt and then used command:

ffmpeg -f concat -i inputs.txt -c copy mergedVideo.mp4

Output:

ffmpeg  -f concat -i inputs.txt -c copy mergedVideo.mp4
ffmpeg version 5.0.1 Copyright (c) 2000-2022 the FFmpeg developers
  built with clang version 12.0.1
  configuration: --prefix=/Users/runner/miniforge3/conda-bld/ffmpeg_1649114094397/_h_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_pl --cc=arm64-apple-darwin20.0.0-clang --disable-doc --disable-openssl --enable-demuxer=dash --enable-gnutls --enable-gpl --enable-hardcoded-tables --enable-libfreetype --enable-libopenh264 --enable-neon --enable-libx264 --enable-libx265 --enable-libaom --enable-libsvtav1 --enable-libxml2 --enable-libvpx --enable-pic --enable-pthreads --enable-shared --disable-static --enable-version3 --enable-zlib --enable-libmp3lame --pkg-config=/Users/runner/miniforge3/conda-bld/ffmpeg_1649114094397/_build_env/bin/pkg-config --enable-cross-compile --arch=arm64 --target-os=darwin --cross-prefix=arm64-apple-darwin20.0.0- --host-cc=/Users/runner/miniforge3/conda-bld/ffmpeg_1649114094397/_build_env/bin/x86_64-apple-darwin13.4.0-clang
  libavutil      57. 17.100 / 57. 17.100
  libavcodec     59. 18.100 / 59. 18.100
  libavformat    59. 16.100 / 59. 16.100
  libavdevice    59.  4.100 / 59.  4.100
  libavfilter     8. 24.100 /  8. 24.100
  libswscale      6.  4.100 /  6.  4.100
  libswresample   4.  3.100 /  4.  3.100
  libpostproc    56.  3.100 / 56.  3.100
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x1561044a0] Auto-inserting h264_mp4toannexb bitstream filter
Input #0, concat, from 'inputs.txt':
  Duration: N/A, start: -0.064000, bitrate: 1424 kb/s
  Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(progressive), 1920x1080 [SAR 1:1 DAR 16:9], 1355 kb/s, 50 fps, 50 tbr, 12800 tbn
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 16000 Hz, mono, fltp, 68 kb/s
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
File 'mergedVideo.mp4' already exists. Overwrite? [y/N] y
Output #0, mp4, to 'mergedVideo.mp4':
  Metadata:
    encoder         : Lavf59.16.100
  Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(progressive), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 1355 kb/s, 50 fps, 50 tbr, 12800 tbn
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 16000 Hz, mono, fltp, 68 kb/s
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
frame=    0 fps=0.0 q=-1.0 size=       0kB time=00:00:00.06 bitrate=   6.0k[mov,mp4,m4a,3gp,3g2,mj2 @ 0x154f28b20] Auto-inserting h264_mp4toannexb bitstream filter
frame=  166 fps=0.0 q=-1.0 Lsize=     583kB time=00:00:03.39 bitrate=1407.4kbits/s speed= 179x    
video:550kB audio:29kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.737394%

Unfortunately the result is different then I expected:
movies comparison

The output is longer than the length of two inputs. Any thoughts?

Also I tried using different commands:

ffmpeg  -f concat -i inputs.txt -c copy mergedVideo.mp4

or set the framerate:

ffmpeg -r 50 -f concat -i inputs.txt -c copy mergedVideo.mp4

What is also weird that I have the same problem when using moviepy library.

from moviepy.editor import VideoFileClip, concatenate_videoclips
videos = [VideoFileClip("0.mp4"), VideoFileClip("0.mp4")]
concatenate_videoclips(videos).write_videofile('mergedVideo.mp4')

Update ffprobe command for output file

ffprobe -v error -select_streams v -show_entries stream=codec_name,time_base,start_pts,start_time,duration -of default=noprint_wrappers=1 mergedVideo.mp4 
codec_name=h264
time_base=1/12800
start_pts=0
start_time=0.000000
duration=3.380000

For input:

ffprobe -v error -select_streams v -show_entries stream=codec_name,time_base,start_pts,start_time,duration -of default=noprint_wrappers=1 0.mp4          
codec_name=h264
time_base=1/12800
start_pts=0
start_time=0.000000
duration=1.660000

The duration supposed to be 2*1.66 = 3.32 and but it's 3.38.

Content of the inputs.txt

file '0.mp4'
file '0.mp4'
  • How do you understand movies comparison picture without the marks on the axes? Please provide comparisons in the measurable values. Run this command for the source files and the result one: `ffprobe -v error -select_streams v -show_entries stream=codec_name,time_base,start_pts,start_time,duration -of default=noprint_wrappers=1 FILENAME` and update the question with the results. Also what's inside the `inputs.txt`? – seeker Dec 27 '22 at 18:47
  • @seeker Content of inputs.txt: `file '0.mp4' file '0.mp4'` The X axis corresponds to the time. As you can see on screen I provided, the merged video is longer and the audio is shifted. – Rostyslav Mosorov Dec 28 '22 at 11:46

0 Answers0