FFMPEG - Concating multiple clips produce corrupted output (freeze video, audio loss, lengthy duration)

Noyan Ahmed :

I am trying to concat multiple clips using FFMPEG

My input videos have the following details:

input1.mp4

ffprobe version 3.4.6-0ubuntu0.18.04.1 Copyright (c) 2007-2019 the FFmpeg developers
  built with gcc 7 (Ubuntu 7.3.0-16ubuntu3)
  configuration: --prefix=/usr --extra-version=0ubuntu0.18.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
  libavutil      55. 78.100 / 55. 78.100
  libavcodec     57.107.100 / 57.107.100
  libavformat    57. 83.100 / 57. 83.100
  libavdevice    57. 10.100 / 57. 10.100
  libavfilter     6.107.100 /  6.107.100
  libavresample   3.  7.  0 /  3.  7.  0
  libswscale      4.  8.100 /  4.  8.100
  libswresample   2.  9.100 /  2.  9.100
  libpostproc    54.  7.100 / 54.  7.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input1.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.20.100
  Duration: 00:05:11.75, start: 0.000000, bitrate: 1338 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 1204 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
    Metadata:
      handler_name    : ISO Media file produced by Google Inc. Created on: 11/09/2018.
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 125 kb/s (default)
    Metadata:
      handler_name    : ISO Media file produced by Google Inc. Created on: 11/09/2018.

input2.mp4

ffprobe version 3.4.6-0ubuntu0.18.04.1 Copyright (c) 2007-2019 the FFmpeg developers
  built with gcc 7 (Ubuntu 7.3.0-16ubuntu3)
  configuration: --prefix=/usr --extra-version=0ubuntu0.18.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
  libavutil      55. 78.100 / 55. 78.100
  libavcodec     57.107.100 / 57.107.100
  libavformat    57. 83.100 / 57. 83.100
  libavdevice    57. 10.100 / 57. 10.100
  libavfilter     6.107.100 /  6.107.100
  libavresample   3.  7.  0 /  3.  7.  0
  libswscale      4.  8.100 /  4.  8.100
  libswresample   2.  9.100 /  2.  9.100
  libpostproc    54.  7.100 / 54.  7.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input2.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.20.100
  Duration: 00:00:05.62, start: 0.000000, bitrate: 2479 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1260x720 [SAR 1:1 DAR 7:4], 2376 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : SoundHandler

I have tried 2 approaches but none seemed to work properly.

Approach #1: Using ffmpeg concat filter

Steps:

ffmpeg -i input1.mp4 -qscale:v 1 intermediate1.mpg
ffmpeg -i input2.mp4 -qscale:v 1 intermediate2.mpg
cat intermediate1.mpg intermediate2.mpg > intermediate_all.mpg
ffmpeg -i intermediate_all.mpg -qscale:v 2 output.mp4

Approach #2: Using ffmpeg concat demuxer along with timebase handling

Steps:

ffmpeg -i input1.mp4 -s hd720 -r 30000/1001 -video_track_timescale 30k -c:a copy input1-converted.mp4
ffmpeg -i input2.mp4 -s hd720 -r 30000/1001 -video_track_timescale 30k -c:a copy input2-converted.mp4
ffmpeg -f concat -safe 0 -i vidlist.txt -c copy output.mp4

References:

Expectations:

One resultant clip with both inputs merged one after another with proper length(sum of inputs) and no video freeze/audio loss.

Results:

One resultant clip with both inputs merged one after another with lengthy duration(more than the sum of inputs) and video freeze and sometimes audio loss as well.

llogan :

Your inputs must have the same parameters, but yours vary in width, frame rate, timescale, audio sample rate, and audio channel layout. Since input1.mp4 is the main feature you can re-encode input2.mp4 to match the properties of input1.mp4:

ffmpeg -i input2.mp4 -filter_complex "[0:v]pad=1280:720:-1:-1,fps=30000/1001[v];[0:a]aformat=sample_rates=44100:channel_layouts=stereo[a]" -map "[v]" -map "[a]" input2b.mp4

Then use the concat demuxer to concatenate them. Create input.txt:

file 'input1.mp4'
file 'input2b.mp4'

Concatenate:

ffmpeg -f concat -i input.txt -c copy output.mp4

This leaves input1.mp4 untouched: the process is faster, and preserves the quality of input1.mp4.
Even better is to re-create a new input2.mp4 from the original source while setting the proper parameters. This will avoid generation loss from re-encoding a new file from it.