[FFmpeg-devel] [PATCH][TESTERS WANTED] avfilter: add apitch filter

[Tim Jones]

On May 12, 2019, at 11:51 AM, Nicolas George <george at nsup.org> wrote:
> 
> Paul B Mahol (12019-05-12):
>> Calling atempo filter atempo when it also modifies pitch is bad for users and
>> at same time not having apitch filter, user would think that they can
>> not alter pitch.
>> Sorry if you can not understand my fears.
> 
> As I have pointed to you (but you made a show of misunderstanding on
> purpose), changing the pitch and changing the speed of an audio signal
> are fundamentally the same thing, they are connected by the sample rate.
> 
> In my experience, most people are aware of that, including completely
> non-technical people: they know that if you speed up or down a sound,
> its pitch changes.

Coming from the audio world, tempo, and pitch are different things.  Using a smart algorithm. I can speed up the tempo of clip without changing the pitch.  Or, inversely, I can modify the pitch without changing the tempo.  We look at "tempo" as beats per period (usually minutes).  We look at pitch as the "tone and timbre" of a given sound (transposing a note from D to F#, for example).

> The documentation, of course, can be enhanced to make sure it contains
> all keyword a user is likely to search. And if the options can be
> tweaked to allow setting exactly the wanted output in the most
> convenient way (like we have a setdar, even though only the SAR exists
> in the library), it is even better.

This would be helpful since I had previously looked into adjusting the playback rate without the associate "Alvin and the Chipmunks" effect and didn't uncover anything within a deep DDG and Google search.

--
Tim