Insert Random silence multiple times between Audios in ffmpeg

Question

suppose I have MP3 of around 1 minute duration and increase its duration longer.Duration can be any.

I want to randomly add N seconds of silence to that audio.

I can generate the silence like below

ffmpeg -f lavfi -i anullsrc=r=44100:cl=mono -t <seconds> -q:a 9 -acodec libmp3lame out.mp3

And I can insert silence to audio like below

ffmpeg -i in.wav -filter_complex "anullsrc,atrim=0:4[s];[0]atrim=0:14[a];[0]atrim=14,asetpts=N/SR/TB[b];[a][s][b]concat=3:v=0:a=1" out.wav

Is there anyway to insert silence at multiple areas.With php I can generate random time to insert based on 60 seconds audio like below.

$arr = [];
$arr[3] = 2; //here 3 is original audio insert time and 2 is the duration of silence
$arr[6] = 3;  //here 6 is original audio insert time and 3 is the duration of silence
$arr[10] = 1;
$arr[12] = 3;

Now I want to insert silence between seconds based on above array like

2 seconds silence at 3rd second
3 seconds silence at 6th second
1 second silence at 10th second

and son on..

Is the duration of silence chosen by you or some random process? Is the location of insertion chosen by you or some random process? — Gyan, Sep 23 '21 at 16:11
Hi , right now I am generating the randomness via php , you can see the array thats generated. — Gracie williams, Sep 23 '21 at 16:16
I can run for loop with duration and location and generate some ffmpeg code aswel.(by concatenation) — Gracie williams, Sep 23 '21 at 16:32

score 2 · Answer 1 · answered Sep 23 '21 at 16:43

2

I assume the location and duration of silences are known to you before ffmpeg execution.

Using as an example,

2 seconds silence at 3rd second
3 seconds silence at 6th second
1 second silence at 10th second

you would run

ffmpeg -i in.wav -af "asetpts='PTS+gte(T\,2)*2/TB+gte(T\,5)*3/TB+gte(T\,9)*1/TB',aresample=async=1" out.wav

The asetpts filter preserves the timestamps of the interval 0 to 2. It increases timestamps of all frames with timestamp 2s or higher by 2 seconds. It further adds 3 seconds to all frames with timestamp >= 5, and another second to all timestamps 9 and higher. T refers to source timestamps.

The aresample filter then plugs all timestamp gaps with silence.

answered Sep 23 '21 at 16:43

Gyan

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Thanks but In my for loop where do I update the location.. duration i can change here i guess *2/TB , *3/TB , *1/TB – Gracie williams Sep 23 '21 at 17:06
It got 2 ,5 and , 8.. but . i have 3 , 6 and 10.. its little confusing – Gracie williams Sep 23 '21 at 17:07
`3rd second` means `T=2` – Gyan Sep 23 '21 at 17:09
ok its should be minus 1 ? got it :) let me try – Gracie williams Sep 23 '21 at 17:10
Thanks can add some fade in fade out between these silence ? – Gracie williams Sep 23 '21 at 17:32

Insert Random silence multiple times between Audios in ffmpeg

1 Answers1