Audio SYNC question regarding a FPS conversion from 24 FPS to 25 FPS



A question for the more experienced postpro experts here...

A film i worked on had to change its FPS from 24 FPS to 25 FPS and therefore now has a different duration.

Unfortunately i produced the sound design to the 24 FPS version of the film. I exported the mix of my sound design as a 48Khz WAV file.

By which factor do i have to pitch my exported WAV up or down to match the films new duration to ensure everything is back in sync if i align film and WAV at frame 0?

The tiny change in pitch does not matter (sonically) in my scenario. Therefore i want to do a pitch and not timestretch to avoid artifacts.

Any help would be greatly appreciated!

Thanks, D.


Posted 2013-08-23T15:42:39.503

Reputation: 1

it sounds though that you've been working with a 24fps video file. If their change is in the final edit, why not give them the 24fps sound file, let them sync that up to the 24fps video project and then re-export to 25fps. – None – 2013-08-23T18:58:56.593



Altering the speed from 24/25 FPS would mean speeding it up by 4.16666%. By Pitching up the sound by 70 cents you will speed the video up by 4.1250% or by pitching it up by 71 cents you will go to 4.1854% In both cases the new file will not have an absolutely correct length, but if the total length of the video is not more than 20 minutes it should be ok.

Pitching it up though by such an amount might drastically alter your mix (especially certain sound effects) and if there is dialog present, change the performance of an actor.

In my experience a good timestretch algorithm works better in this case, since it can be set at the exact value of the frame change and keep the mix more or less intact.

In any case you can try both ways and see which works best, and if still not sure, let the director choose the one that better fit his needs :)


Posted 2013-08-23T15:42:39.503

Reputation: 11

Thanks so much for all the answers. This was really helpful. Cheers! – dodo – 2013-08-24T14:12:43.283

I am glad i could help :) – Sporkstudio – 2013-08-24T17:10:55.023


There should be pre-set sample rate values you can 'force' upon a audio file import into PT (under the SRC section) - there should be one from Film to PAL I believe.

And/or the XForm plugin should have a TCE/Varispeed preset for this rate conversion as well.

Those are probably the easiest two ways to do it.


Posted 2013-08-23T15:42:39.503

Reputation: 6 616

Hi, Thanks for the answer, but i dont own protools and therefore can't use AS plugins etc. Is there a VST alternative, or can anyone help with just the factor/percentage? Also because I want to be sure i am only pitching and not doing any timestretching. Thanks! – dodo – 2013-08-23T16:55:32.090

check out speed:

– Arnoud Traa – 2013-08-25T12:01:49.500



So the 25 fps sound should be 4.16666% faster

Gábor Császár

Posted 2013-08-23T15:42:39.503

Reputation: 23


You could speed vary your DAW + 4.16666% faster, and re-record the output on a 48K machine.

Douglas Murray

Posted 2013-08-23T15:42:39.503

Reputation: 256