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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