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Add audio at specific time in video using ffmpeg


I want to add an M4A audio of 5s duration to an MP4 video file. I have already tried the -itsoffset command of ffmpeg.


ffmpeg -i a.mp4 -itsoffset 00:00:10 -i b.m4a -map 0:0 -map 1:0 -preset ultrafast o.mp4

Commandline output


ffmpeg -i psy.mp4 -itsoffset 00:00:10 -i cut.m4a -map 0:0 -map 1:0 -c:v copy -preset ultrafast -y out.mp4
ffmpeg version N-50911-g9efcfbe Copyright (c) 2000-2013 the FFmpeg developers
built on Mar 13 2013 21:26:48 with gcc 4.7.2 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
le-libass --enable-libbluray --enable-libcaca --enable-libfreetype --enable-libg
sm --enable-libilbc --enable-libmp3lame --enable-libopencore-amrnb --enable-libo
pencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-li
bschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-lib
twolame --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enabl
e-libvpx --enable-libx264 --enable-libxavs --enable-libxvid --enable-zlib
libavutil      52. 19.100 / 52. 19.100
libavcodec     55.  0.100 / 55.  0.100
libavformat    55.  0.100 / 55.  0.100
libavdevice    54.  4.100 / 54.  4.100
libavfilter     3. 45.103 /  3. 45.103
libswscale      2.  2.100 /  2.  2.100
libswresample   0. 17.102 /  0. 17.102
libpostproc    52.  2.100 / 52.  2.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'psy.mp4':
Metadata:
major_brand     : mp42
minor_version   : 0
compatible_brands: isommp42
creation_time   : 2013-12-03 03:22:01
Duration: 00:04:12.17, start: 0.000000, bitrate: 723 kb/s
Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yu
v420p, 640x360, 624 kb/s, 23.98 fps, 23.98 tbr, 48k tbn, 47.95 tbc
Metadata:
  handler_name    : VideoHandler
Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 96
kb/s
Metadata:
  creation_time   : 2013-12-03 03:22:02
  handler_name    : IsoMedia File Produced by Google, 5-11-2011
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from 'cut.m4a':
Metadata:
major_brand     : M4A
minor_version   : 512
compatible_brands: isomiso2
encoder         : Lavf55.0.100
Duration: 00:00:05.24, start: 0.237460, bitrate: 99 kb/s
Stream #1:0(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 96
kb/s
Metadata:
  handler_name    : SoundHandler
Codec AVOption preset (Set the encoding preset (cf. x264 --fullhelp)) specified
for output file #0 (out.mp4) has not been used for any stream. The most likely r
eason is either wrong type (e.g. a video option with no video streams) or that i
t is a private option of some encoder which was not actually used for any stream
.
Output #0, mp4, to 'out.mp4':
Metadata:
major_brand     : mp42
minor_version   : 0
compatible_brands: isommp42
encoder         : Lavf55.0.100
Stream #0:0(und): Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 640x360, q=
2-31, 624 kb/s, 23.98 fps, 48k tbn, 48k tbc
Metadata:
  handler_name    : VideoHandler
Stream #0:1(und): Audio: aac ([64][0][0][0] / 0x0040), 44100 Hz, stereo, s16
, 128 kb/s
Metadata:
  handler_name    : SoundHandler
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Stream #1:0 -> #0:1 (aac -> libvo_aacenc)
Press [q] to stop, [?] for help
frame=  916 fps=0.0 q=-1.0 size=     865kB time=00:00:38.16 bitrate= 185.7kbits/
frame= 1758 fps=1749 q=-1.0 size=     865kB time=00:01:13.28 bitrate=  96.7kbits
frame= 2477 fps=1645 q=-1.0 size=     865kB time=00:01:43.26 bitrate=  68.6kbits
frame= 3182 fps=1586 q=-1.0 size=     865kB time=00:02:12.67 bitrate=  53.4kbits
frame= 3961 fps=1580 q=-1.0 size=     865kB time=00:02:45.16 bitrate=  42.9kbits
frame= 4904 fps=1631 q=-1.0 size=     865kB time=00:03:24.49 bitrate=  34.7kbits
frame= 5667 fps=1615 q=-1.0 size=     865kB time=00:03:56.31 bitrate=  30.0kbits
frame= 6046 fps=1549 q=-1.0 Lsize=   19345kB time=00:04:12.12 bitrate= 628.6kbit
s/s
video:19234kB audio:83kB subtitle:0 global headers:0kB muxing overhead 0.146119%

The problem is: it does start at 00:00:10 but it keeps repeating after every 10s. (You can notice this only when you play the whole video without touching the seekbar.)


When I play this video on Android, then the audio starts from the beginning. It plays fine with VLC.


Expected result: Silence in video till specified time, then my audio, and again silence after audio.



Answer



Ok finally I solved the problem by adding just 1 option -async


ffmpeg -y -i a.mp4 -itsoffset 00:00:30 sng.m4a -map 0:0 -map 1:0 -c:v copy -preset ultrafast -async 1 out.mp4

By default audio/video timestamps are stretched to match each other; which was my problem of audio starting from intial even after giving itsoffset.


As per Ffmpeg Doc using -async 1 corrects the initial timestamp of audio only. I know that this option is deprecated; but anyhow it solved my case.


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