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

[Mark Filipak]

On 01/06/2025 15.38, Paul B Mahol wrote:
> 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?

It's stereo ac3, 192kbpx. Do you need the files to run experiments?