[FFmpeg-user] isolate 'voices', move them, and mix into another audio stream

[Richard Bartczak]

Am 01.06.25 um 17:48 schrieb Paul B Mahol:
> On Sun, Jun 1, 2025 at 3:40 PM Mark Filipak <markfilipak.imdb at gmail.com>
> wrote:
>
>> I have two ac3 audio streams. One is 'voices+noise', the other is just
>> 'noise' -- no voices. I want
>> to take 'voices+noise', remove 'noise' leaving just 'voices', then mix
>> 'voices' into a latter,
>> clipped version, call it 'sounds'. I could do it with Audacity, but I'd
>> like to do it with FFmpeg,
>> if possible.
>>
>> I seek experienced guidance because I've never done this before and I want
>> to use the best audio
>> mixer 'filter' available -- knowing what's best comes only via experience.
>>
>> The full story:
>>
>> "2001, A SPACE ODYSSEY" has a tedious, 2:58.136 prelude that is just
>> 'noise', after which the MGM
>> Lion appears. When I made an mp4, I cut 'm2ts 0..178.136' out leaving just
>> 'm2ts 178.136...', which
>> is now 'mp4 0...', which begins with the MGM Lion.
>>
>> When I finished, I discovered that in their comments track, Keir Dullea
>> and Gary Lockwood introduce
>> themselves during that 'noise'. Their 'voices' spans 'm2ts 0..34.034'.
>>
>> I want to take 'm2ts 0..34.034', remove the 'noise' so that only 'voices'
>> is left, then mix 'voices'
>> into 'mp4 0..34.034', over the MGM Lion. There's a little more clipping
>> and joining to be done but I
>> can handle that.
>>
> Need actual files.
>
>
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On youtube you will find a lot of ac-3 files, e.g.:

yt-dlp -F -o "%(title)s.%(ext)s"  -R infinite -N 4  --cookies 
cookies.txt  --no-playlist 
"https://www.youtube.com/watch?v=m1m7S3YVIP4&list=PLGI9nth6470EEmULYPzDn4rOiOmegfb9_&index=2&pp=iAQB"

With  the parameter -F you will get the complete list of all stream IDs :

140     m4a   audio only      2 │   113.31MiB  129k https │ audio only  
         mp4a.40.2  129k 44k [de] medium, m4a_dash
251     webm  audio only      2 │   108.51MiB  124k https │ audio only  
         opus       124k 48k [de] medium, webm_dash
380     m4a   audio only      6 │   336.15MiB  384k https │ audio only  
         ac-3       384k 48k [de] high, m4a_dash
328     m4a   audio only      6 │   336.15MiB  384k https │ audio only  
         ec-3       384k 48k [de] high, m4a_dash
602     mp4   256x144     12    │ ~ 105.85MiB  121k m3u8  │ 
vp09.00.10.08  121k video only
269     mp4   256x144     24    │ ~ 154.51MiB  177k m3u8  │ avc1.4D400C  
   177k video only
160     mp4   256x144     24    │    43.84MiB   50k https │ avc1.4d400c  
    50k video only          144p, mp4_dash

with -f + ID you will get the file  :

yt-dlp -f 380 -o "%(title)s.%(ext)s"  -R infinite -N 4  --cookies 
cookies.txt  --no-playlist 
"https://www.youtube.com/watch?v=m1m7S3YVIP4&list=PLGI9nth6470EEmULYPzDn4rOiOmegfb9_&index=2&pp=iAQB"

yt-dlp refer to github

Regards

Richard