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

[Paul B Mahol]

On Sun, Jun 1, 2025 at 7:37 PM Mark Filipak <markfilipak.imdb at gmail.com>
wrote:

> On 01/06/2025 14.26, Paul B Mahol wrote:
> >> 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.
> >
> > I need exact files that Mark have.
>
> Why, Paul? This isn't troubleshooting. It's how-to.
>
> I need to do this:
>
> 1) 'voices' = mix('voices+noise',invert('noise')). 'voices+noise' is an
> existing ac3. 'noise' is
> another ac3 that is identical but without voices. 'amix' is a mixer, but
> is it the best mixer? More
> important: I don't know of any audio filter that will invert().
>
> followed by this:
>
> 2) output = mix('audio','voices'). 'audio' is an existing ac3.
>

How many audio channels every file have?


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