FFMpeg - add sound to video that already contain sound

Question

Here is what I have: input1.avi - video that contain sounds. input2.avi - video that doesn't contain sounds. music.mp3 - audio file.

I want to add background music(music.mp3 file) to the video.

C:\\input1.avi -i C:\\music.mp3 -shortest -c:v copy -c:a copy C:\\output1.avi then output1.avi is the same as input1 - movie with sounds but without the background music (music.mp3)

when I try to use the other file (video without sounds):

C:\\input2.avi -i C:\\music.mp3 -shortest -c:v copy -c:a copy C:\\output2.avi then output2.avi is the same as input2 + it have the background music.

I tried to execute this too:

C:\ffmpeg\bin>ffmpeg -i C:\input.avi -i C:\music.mp3 -shortest -c:v copy -filter_ complex "[1]volume=1.5[1a];[0][1a]amerge[a]" -map 0:v -map "[a]" -ac 2 C:\output1.avi

but got the next error messsage:

ffmpeg version N-78949-g6f5048f Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 5.3.0 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
le-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --
enable-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm --enable-l
ibilbc --enable-libmodplug --enable-libmfx --enable-libmp3lame --enable-libopenc
ore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --ena
ble-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable
-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --ena
ble-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx
264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable
-lzma --enable-decklink --enable-zlib
  libavutil      55. 19.100 / 55. 19.100
  libavcodec     57. 27.101 / 57. 27.101
  libavformat    57. 28.100 / 57. 28.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 39.100 /  6. 39.100
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
Input #0, avi, from 'C:\output1.avi':
  Metadata:
    encoder         : Lavf57.28.100
  Duration: 00:02:05.76, start: 0.000000, bitrate: 450 kb/s
    Stream #0:0: Video: mpeg4 (Simple Profile) (XVID / 0x44495658), yuv420p, 720
x480 [SAR 1:1 DAR 3:2], 440 kb/s, 25 fps, 25 tbr, 25 tbn, 25 tbc
    Stream #0:1: Audio: mp3 (U[0][0][0] / 0x0055), 44100 Hz, stereo, s16p, 128 k
b/s
[mp3 @ 00000000005abc20] Skipping 0 bytes of junk at 32370.
Input #1, mp3, from 'C:\music.mp3':
  Metadata:
    title           : Broadcast News Package - News Intro
    artist          : After Effects News Template
  Duration: 00:01:57.89, start: 0.025057, bitrate: 194 kb/s
    Stream #1:0: Audio: mp3, 44100 Hz, stereo, s16p, 192 kb/s
    Metadata:
      encoder         : Lavc56.26
[Parsed_amerge_1 @ 0000000000610200] No channel layout for input 1
[Parsed_amerge_1 @ 0000000000610200] No channel layout for input 2
[AVFilterGraph @ 00000000005ddfe0] The following filters could not choose their
formats: Parsed_amerge_1
Consider inserting the (a)format filter near their input or output.
Error configuring complex filters.
I/O error

So why input1 does not contain the background music? and how can I decrease or increase the volume of music.mp3 file?

Answer 1

One way to do this is to use ffmpeg and Sox ( http://sox.sourceforge.net ) together:

1. Extract the current soundtrack from the original video using ffmpeg
2. Use Sox to merge the extracted soundtrack and your background music
3. Use ffmpeg to put the new merged audio track in place of the extracted original soundtrack

This sox command will allow you merge two audio files, setting the volumes as you wish:

sox -m -v videoVol ./temp/videoAudio.mp3 -v musicVol ./temp/tempMusic.mp3 ./temp/mixedAudio.mp3

There are a couple of thing to watch out for:

• you need to check the sample rates match for the audio and if not then adjust them so they do (see below for sox syntax to change an audio rate)
• you probably want to reduce or extend your music length so it matches the video soundtrack before you do the merge

Sox syntax to change audio rate:

sox ./temp/videoAudio.mp3 -r 44100 ./temp/videoAudioAdjusted.mp3