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

[Michael Koch]

Am 28.04.2021 um 23:34 schrieb Bo Berglund:
> On Wed, 28 Apr 2021 11:35:47 +0200, Michael Koch <astroelectronic at t-online.de>
> wrote:
>
>>> I had tested this (which I found by googling) before I posted:
>>>
>>> ffmpeg -i input20.mp4 -filter:a "atempo=1.25" -vn output20.mp4
>>>
>>> There were no errors displayed but the resulting file *ONLY* contains the audio
>>> part, I neeed both and the audio change must not change the length or lipsync of
>>> the file.
>> Sure, that's because -vn means "no video output". Just remove this
>> option and then your output file will contain audio and video.
> OK, that included the video...
> But now there is no lip-sync at all. Seems to drift longer apart during the
> video playing. Audio and video running at different speeds.

The atempo filter changes the length of the audio track, while keeping 
the pitch and the sample rate constant. As shown in the 5th command line 
in chapter 3.4 in my book.
If you want to change only the audio pitch (and keep the sample rate and 
length constant), you must use a combination of asetrate, atempo and 
aresample filters. That's the 2nd command line in that chapter.

Michael