[FFmpeg-user] Replacing First 90 Seconds of a Video with Silence or with Another Audio Clip

[a@fumatic.org]

On 01/18/2016 10:02 PM, Ryan Williams
wrote:




On Tuesday, 19 January 2016 02:13 Sam Logan <shapableline at gmail.com> wrote:



I have a video AVI file, "Video.avi", consisting of a video and an 
audio track, and a separate audio file, "Audio.mp3". I want to do the 
following two things:

(1)

First, I want to produce a version of the video, "OutputSilenced.avi", 
which would be identical to the original video except that the first 
90 seconds of the video's audio are replaced with silence (to clarify, 
I want to REPLACE, as in overwrite, the first 90 seconds, NOT insert 
90 seconds of silence to push the audio back 90 seconds).



-af "volume=enable='lte(t,90)':volume=0"

http://ffmpeg.org/ffmpeg-filters.html#volume
http://ffmpeg.org/ffmpeg-filters.html#Timeline-editing



(2)

Second, I want to produce a version of the video, 
"OutputReplaced.avi", which would be identical to the original video 
except that the first 90 seconds of the video's audio are replaced 
with the first 90 seconds of "Audio.mp3" (again, to be clear, I want 
to REPLACE, as in overwrite, the first 90 seconds, NOT insert 90 
seconds of audio to push the original audio back 90 seconds).

How commands would I use to do this with FFmpeg? Ideally, I would like 
to just remux without doing any re-encoding. Thanks in advance.


Only way I can think of is to use a combination of the volume filter above to suppress the audio form the video and chain it with 'amix' to create a new audio track.

If you run into volume level problems using 'amix' try a combination of 'amerge' to make it a 4 channel track then 'pan' to change it back into stereo.

http://ffmpeg.org/ffmpeg-filters.html#amix
http://ffmpeg.org/ffmpeg-filters.html#amerge-1
http://ffmpeg.org/ffmpeg-filters.html#pan





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step 1)  Stop being a tool with the
all caps. be polite
You catch more flies with honey, 
than you do with vinegar.


step 2)
grab just the audio from your video 90 seconds in:
ffmpeg -ss 00:01:30  -i in.mp4 -vn  out.mp3

step 3)
concat your audio.mp3 with the out.mp3 you just made

ffmpeg -i "concat:audio.mp3|out.mp3"   -c copy all.mp3

step 4)
take the video stream from the original video and mux in all.mp3

ffmpeg -i in.mp4 -i all.mp3 -map 0:0 -map 1:0 -c copy done.mp4

step 5) record a blank 90 secs of audio
and repeat the steps 3 and 4 with it instead of audio.mp3.