View Full Version : Converting 25p footage with audio to 24p

08-01-2014, 09:45 AM
I have 25p footage which includes audio (voice) for documentary.
How to convert it to 24p, while maintain sync, preferably also maintain the correct audio pitch?
Software I have include Edius 6, Adobe AE CC, Adobe Audition CC, Adobe Premiere Pro CC and TMPGEnc Video Mastering Works 5.

I assume that adding music would better be done while editing on the designated distribution fame rate. Is that correct?

Michael Carter
08-06-2014, 10:59 AM
I've had to convert edits from 24p to 29.97 without changing speed, and I've rendered from FCP to the new frame rate. Looks surprisingly good, but you can see some choppiness.

Going from 25 to 24, you're throwing out time vs. adding it so it may be better.

Your other option is to conform the edit - it will get a little longer (a small percentage) and the audio pitch will go down but you'll have frame-accurate video.

You can then change the pitch of the audio (Audacity does a great job of this, especially for a tweak this minor) if it sounds too low. Export the audio, bring into audacity or protools, change pitch but not tempo and re-import (or try your NLE's audio filters). The precentage change of pitch is simple math.

But ONLY conform what's essential - video and synched audio (voice). Don't make the audio resample all the music, sound effects, etc. You'll get much better audio quality.

08-06-2014, 12:07 PM

10-08-2014, 03:16 PM
I have done this many of times, I use to shoot with PAL cameras here in North America to derive 24p from 50i long before 24p was available on cheaper prosumer cameras like the DVX100, XL2, etc..

Basically what you can do is drop your 25p file to a 24p timeline. It matches 1 frame from your source material to 1 frame on your timeline so effectively what happens now is your finished video should be around 4% longer because for each second of time you had in your original footage you now have one extra frame on the new timeline. ie. every 24 seconds you get an extra one. Anyway, that math is not important.

If at this stage you think you can hear a pitch difference in the final video after being stretched by around 4% then you will have to do some magic on the audio file. This is easy to do with Cool Edit, Adobe Edition, etc..

Using the sound file from the 25p video version, open only the audio and stretch it to match the new length from your 24p timeline. It's around 4% longer but not exactly 4% so don't enter a percentage stretch value.. just type in the new time value. If your only option is to enter a percentrage for stretch then try 1.0416666.

As you suspected it is better to re-add your music back into your new 24p timeline, but if not, you can still use the step above to stretch and pitch shift the file so that it sounds exactly like the original did.

If all this is too crazy for you, you can try googling DVFILM convert or something if they are still around.

Good luck,

10-08-2014, 11:45 PM
Thanks, Dennis.Thanks, Dennis.