[FFmpeg-user] Howto sync two audio streams and mix them

[Thomas Seilund]

Denis Mysenko writes:

>  You cannot use 'itsoffset' to delay an audio stream, you need 'adelay' audiofilter instead.
>
> Eg. [1:0]adelay=10|10[out1] to produce a 10 second delayed audio from stream 1:0 and call it out1
>
> So your case could be:
> ffmpeg -y -i 20150416203941.broadcast.ts -i 
> 20150416203941.broadcast.ts -filter_complex "[0:1]adelay=10|10[track1];[track1][1:2]amix[mixout]" -c:v 
> copy -c:a aac -b:a 128k -ar 44100 -strict -2 -map 0:0 -map [mixout] -f flv test1.flv
>
> Note that 10 second delay is specified twice – separately for left and right channels
>
> Суббота, 18 апреля 2015, 9:38 +02:00 от Thomas Seilund <tps at netmaster.dk>:
>>Hi all
>>
>>I have an mpegts container with one video and two audio streams.
>>
>>I what to mix the two audio streams. At the same time the second audio
>>stream must be delayed 10 seconds to match the first audio stream.
>>
>>Here is what I have as input
>>
>>tps at t420:~/video/test$ ffprobe -i 20150416203941.broadcast.ts
>>ffprobe version N-69238-g2699a37 Copyright (c) 2007-2015 the FFmpeg
>>developers
>>   built on Feb 24 2015 18:13:15 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
>>   configuration: --enable-gpl --enable-libmp3lame --enable-libvpx --enable-
>>libx264 --enable-version3 --enable-libvorbis --enable-libfreetype --enable-
>>libv4l2 --enable-libfdk-aac --enable-nonfree --enable-libpulse
>>   libavutil      54. 17.100 / 54. 17.100
>>   libavcodec     56. 20.100 / 56. 20.100
>>   libavformat    56. 19.100 / 56. 19.100
>>   libavdevice    56.  4.100 / 56.  4.100
>>   libavfilter     5.  8.101 /  5.  8.101
>>   libswscale      3.  1.101 /  3.  1.101
>>   libswresample   1.  1.100 /  1.  1.100
>>   libpostproc    53.  3.100 / 53.  3.100
>>Input #0, mpegts, from '20150416203941.broadcast.ts':
>>   Duration: 00:00:18.69, start: 1.400000, bitrate: 4186 kb/s
>>   Program 1
>>     Metadata:
>>       service_name    : Service01
>>       service_provider: FFmpeg
>>     Stream #0:0[0x100]: Video: h264 (Constrained Baseline) ([27][0][0][0] /
>>0x001B), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 90k tbn, 50
>>tbc
>>     Stream #0:1[0x101]: Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz,
>>stereo, s16p, 384 kb/s
>>     Stream #0:2[0x102]: Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz,
>>stereo, s16p, 384 kb/s
>>tps at t420:~/video/test$
>>
>>
>>
>>Here is what I do
>>
>>ffmpeg -y -i 20150416203941.broadcast.ts -itsoffset 10 -i
>>20150416203941.broadcast.ts -filter_complex "[0:1][1:2]amix[mixout]" -c:v
>>copy -c:a aac -b:a 128k -ar 44100 -strict -2 -map 0:0 -map [mixout] -f flv
>>test1.flv
>>
>>
>>
>>The two audio streams are mixed ok but the timestamps of the second audio
>>stream are not shifted 10 seconds.
>>
>>
>>
>>Actually, the following command without the -itsoffset 10 parameter
>>produces the same output
>>
>>ffmpeg -y -i 20150416203941.broadcast.ts -i 20150416203941.broadcast.ts -
>>filter_complex "[0:1][1:2]amix[mixout]" -c:v copy -c:a aac -b:a 128k -ar
>>44100 -strict -2 -map 0:0 -map [mixout] -f flv test2.flv
>>
>>
>>
>>What am I doing wrong?
>>
>>Any help would be appreciated.
>>
>>Thanks
>>
>>Thomas S
>>_______________________________________________
>>ffmpeg-user mailing list
>>ffmpeg-user at ffmpeg.org
>>http://ffmpeg.org/mailman/listinfo/ffmpeg-user
>
>
> Sincerely,
> --
> Denis Mysenko, CCNA, MCP, MCSA
> Skype: denismysenko, ICQ: 555955
> Forskarbacken 9 / 209
> 10405 Stockholm, Sweden
>
> Mobile: +46 (0) 70 405 49 04
> _______________________________________________
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> http://ffmpeg.org/mailman/listinfo/ffmpeg-user




Hi Denis

Thank you very much.

You helped a lot.

I ended up with

ffmpeg -y -i 20150416203941.broadcast.ts -filter_complex "[0:2]adelay=10000| 
10000[delayed];[0:1][delayed]amix[mixout]" -c:v copy -c:a aac -b:a 128k -ar  
44100 -strict -2 -map 0:0 -map [mixout] -f flv test2.flv

Thanks

Thomas S