Add another audio over a file with mixed audio tracks in ffmpeg

Question

I have a file that was formed by concatenating three different files: a.mp4, b.mp4 and c.mp4.

do ffmpeg -f concat -i "concat-file.txt" -map 0:v -map 0:a -c:v libx264 -crf 23 -fflags +genpts joined-file.mp4"

After that I run this command, mentioned here: How to add a new audio (not mixing) into a video using ffmpeg?

ffmpeg -i joined-file.mp4 -i audio.mp3 -filter_complex "[0:a][1:a]amerge=inputs=2[a]" -map 0:v -map "[a]" -c:v copy -ac 2 -shortest output.mp4

What is causing this issue?

Thanks. :)

UPDATE:

Here are the commands that I have been running:

ffmpeg -i "middle/b.mp4" -c:v copy -video_track_timescale 30k -c:a aac -ac 6 -ar 44100 -shortest "wrap/b.mp4"
ffmpeg -f concat -i "concat-file.txt" -map 0:v -map 0:a -c:v libx264 -crf 23 -fflags +genpts "joined/abc.mp4"
ffmpeg -i "joined/abc.mp4" -i audio.mp3 -filter_complex "[0:a:0][1:a:0]amerge=inputs=2[a]" -map 0:v -map "[a]" -c:v copy -ac 2 -shortest "final/abc-cmplt.mp4"

Here is the "concat-file.txt":

file 'bits/a.mp4'
file 'wrap/b.mp4'
file 'bits/c.mp4'

All the video files a.mp4, b.mp4 and c.mp4 have their original audio. After I run the commands above, the joint video abc-cmplt.mp4 has combined audio (audio.mp3 plus their own) for the first (a.mp4) and last parts (c.mp4). However, the middle part only has its own audio and the extra audio I am trying to add does not seem to merge with the audio of b.mp4 in the final joint file.

Output of ffmpeg -i bits/a.mp4 -i wrap/b.mp4 -i bits/c.mp4:

ffmpeg version 4.2.2 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 9.2.1 (GCC) 20200122
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'bits/a.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp42mp41
    creation_time   : 2021-03-10T08:50:04.000000Z
  Duration: 00:00:01.05, start: 0.000000, bitrate: 1846 kb/s
    Stream #0:0(eng): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 1080x1920 [SAR 1:1 DAR 9:16], 1462 kb/s, 30 fps, 30 tbr, 30k tbn, 60 tbc (default)
    Metadata:
      creation_time   : 2021-03-10T08:50:04.000000Z
      handler_name    : ?Mainconcept Video Media Handler
      encoder         : AVC Coding
    Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 317 kb/s (default)
    Metadata:
      creation_time   : 2021-03-10T08:50:04.000000Z
      handler_name    : #Mainconcept MP4 Sound Media Handler
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from 'wrap/b.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.29.100
  Duration: 00:00:27.93, start: 0.000000, bitrate: 234 kb/s
    Stream #1:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1080x1920, 231 kb/s, 30 fps, 30 tbr, 30k tbn, 60 tbc (default)
    Metadata:
      handler_name    : VideoHandler
Input #2, mov,mp4,m4a,3gp,3g2,mj2, from 'bits/c.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp42mp41
    creation_time   : 2021-03-10T08:42:52.000000Z
  Duration: 00:00:01.05, start: 0.000000, bitrate: 1829 kb/s
    Stream #2:0(eng): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 1080x1920 [SAR 1:1 DAR 9:16], 1320 kb/s, 30 fps, 30 tbr, 30k tbn, 60 tbc (default)
    Metadata:
      creation_time   : 2021-03-10T08:42:52.000000Z
      handler_name    : ?Mainconcept Video Media Handler
      encoder         : AVC Coding
    Stream #2:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 317 kb/s (default)
    Metadata:
      creation_time   : 2021-03-10T08:42:52.000000Z
      handler_name    : #Mainconcept MP4 Sound Media Handler

Hi @llogan. :) I tried a lot of approaches and learned a few more things about what's happening. I will update the question now with more detail. — Real Noob, Mar 10 '21 at 18:08
@llogan please wait. Should I just type `ffmpeg -i bits/a.mp4 -i wrap/b.mp4 -i bits/c.mp4` in the command line? — Real Noob, Mar 10 '21 at 18:24

llogan · Accepted Answer · 2021-03-11T17:51:35.683

3

All files to be concatenated by the concat demuxer must have these same attributes. b.mp4 has a different H.264 profile and lacks audio. Fix that:

ffmpeg -i "middle/b.mp4" -f lavfi -i anullsrc=cl=stereo:r=48000 -c:v libx264 -profile:v main -video_track_timescale 30k -shortest "wrap/b.mp4"

Then concatenate and mix the audio:

ffmpeg -f concat -i "concat-file.txt" -i audio.mp3 -c:v libx264 -crf 23 -filter_complex "[0:a:0][1:a:0]amerge=inputs=2" -ac 2 "joined/abc.mp4"

Option	Description
`-f lavfi`	Tell ffmpeg the following input is a filter instead of a file.
`-i anullsrc=cl=stereo:r=48000`	Use the anullsrc filter to generate silent stereo audio with 48000 sample rate.
`-profile:v main`	Set H.264 Profile to Main.
`-video_track_timescale 30k`	Set timescale to 30k to match the other videos (`30k tbn`).

edited Mar 11 '21 at 17:51

answered Mar 10 '21 at 19:17

llogan

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Thank you very much @llogan. :) I had been stuck at this problem for many days now and nothing seemed to work. Could you please clear one more doubt of mine? – Real Noob Mar 11 '21 at 02:27
Without my initial command for wrapping `b.mp4` video `ffmpeg -i "middle/b.mp4" -c:v copy -video_track_timescale 30k -c:a aac -ac 6 -ar 44100 -shortest "wrap/b.mp4"`, it was concatenated such that it ran at twice the speed and held at last frame for the rest of the time. Why did that happen? – Real Noob Mar 11 '21 at 02:31
1

@RealNoob Probably different timescale? Or A/V desynchronisation caused by `b.mp4` lacking audio? Just guessing. Need to see the complete log from that command. – llogan Mar 11 '21 at 03:29
Thanks @llogan. :) When you said `b.mp4` has a different profile did you mean `major_brand : isom` compared to `major_brand : mp42`? Is there a place where I can read about different commands that you listed in the answer? This will help me figure out such issues later by mylsef. :) – Real Noob Mar 11 '21 at 03:58
1

@RealNoob H.264 profile (`h264 (Main)` vs `h264 (High)`) as mentioned in link #2 in my answer. *"Is there a place where I can read about different commands that you listed in the answer?"* Sorry, but I don't really understand the question. – llogan Mar 11 '21 at 04:42
I meant commands like `lavfi`, `anullsrc=channel_layout`, `-profile:v main` and `-video_track_timescale` etc. :) I don't understand what they do at all and reading a beginner friendly tutorial will help lot. – Real Noob Mar 11 '21 at 05:22
1

@RealNoob Oh, you meant the options in the commands. I updated the answer with option descriptions. – llogan Mar 11 '21 at 17:52
Thank you very much for adding the explanation @llogan. :) – Real Noob Mar 11 '21 at 23:57

Add another audio over a file with mixed audio tracks in ffmpeg

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