[FFmpeg-user] pitch corecting audio?

[James Heliker]

Thanks Moritz!

If I could access the original 23.976 source audio and apply "-af 
atempo=25*1001/24000", would that accomplish the job without affecting 
pitch in the first place?

Then I could merge the 25fps video with my correctly sped-up audio

Thanks for your help!

- James


On 3/25/2015 2:26 PM, Moritz Barsnick wrote:
> On Wed, Mar 25, 2015 at 11:56:01 -0700, James Heliker wrote:
>> I've got content that was originally 23.976 sped up to 25 for european
>> distribution. I need to shift / correct the audio pitch back down to
>> normal without affecting the timing. Is there a filter for FFmpeg that
>> can accomplish this task? I've been reading through the online
>> documentation for things like atempo and asetrate but they don't seem to
>> do what I need.
> I think those filters will do what you want:
>
> The original was sped up with a pitch shift. It should have been sped
> up without (e.g. with something like atempo), but wasn't. So you - sort
> of - could reverse the process and then do it correctly.
>
>    -af asetrate=r=24000/1001/25*<currentrate>,atempo=25*1001/24000
>
> You may want to resample to an acceptable sample rate (depends on the
> output format, I guess) by using
>    -ar <properrate>
> e.g.
>    -ar 48000
>
> ffmpeg doesn't seem to have a pitch filter, though atempo should be
> something like an inverse operation of that. sox does have a pitch
> filter, IIUC. rubberband also shifts pitch. You could separate video
> and audio, use sox or rubberband on the audio, and remux. You may risk
> losing A/V sync though, due to lost timestamps.
>
> Moritz
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