[FFmpeg-user] Possible to change pitch of audio in a downloaded mp4 file?

[Jim DeLaHunt]

Bo, I don't have expertise in using FFmpeg with audio. But I do want to 
point out that what you say you want appears to be different in 
different parts of your message. Maybe some of these sentences were not 
quite worded correctly?

On 2021-04-28 23:40, Bo Berglund wrote:
> What I wanted was to change the *pitch* of the audio while retaining the
> playback speed!
> So the playback time of the video should be the same as before and the audio
> pitch changed without losing lip sync.

Playback "speed": unchanged. Playback duration: unchanged. Pitch: changed.


On 2021-04-28 23:40, Bo Berglund wrote:
> …What I am after is what VLC can do, namely speed up or down the video playback
> while *retaining* the pitch of the audio without losing lip sync. …

Playback "speed": changed. Playback duration: unchanged. Pitch: unchanged.

Which do you want?

Also, your use of the term "speed" is not clear to me.  Speed is a count 
of something, per unit of time, e.g. beats per second or feet per 
second. Duration is the time taken for something. If you increase the 
beats per second of a recording, and keep the number of beats constant, 
then the duration will become shorter. If the duration changes, you lose 
lip sync. So, maybe you want:

Playback "speed": unchanged. Playback duration: unchanged. Pitch: changed.