Conform 25fps to 24 or 23.976fps

Posted by Andy Wills 
Conform 25fps to 24 or 23.976fps
June 16, 2014 08:21AM
Dear Lafcpug

I have footage which I think was shot on XDCAM.
I have downloaded the SONY XDCAM log and transfer plugin.
This plugin allows me to make QUICKTIME MOVIES of the footage in FCP 7.0.
The MOV files are 25fps.

I have tried putting these files through compressor with "so source frames play at 24fps" selected.
But when I play these on a 24fps timeline in FCP I see a jerk in the motion every 24 frames.

I have also tried outputting the 25fps files from Final Cut as appleprores 422, and conforming them to 23.98 in Cinematools, but I get the same problem.

I'd be very grateful for any advice you could give me on this problem.


Andy Wills
Re: Conform 25fps to 24 or 23.976fps
June 16, 2014 03:28PM
Was the footage shot at 25 fps? If it was shot at 24 fps and you made an error in creating the 25 fps .mov file from it, it probably has a doubled frame every second.

Play that 25 fps .mov file in QuickTime and advance frame-by-frame. Are there doubled frames?

If the 25 fps .mov file really has 25 different frames per second then you can conform it using Cinema Tools or QT Edit to 24 fps. This will slightly slow the movie -- 104% duration -- including the sound. So pitches will drop.

Instead you can use Compressor to semi-conform it by the method you described: "so source frames play at 24 fps". This way the picture gets conformed and it has 104% duration. The sound also has 104% duration, but Compressor has maintained the original sound pitch (a small miracle of sampling). See old post. More details in another old strand.

Since Compressor used that way keeps all your frames (perhaps recompressed) and adds no new frames, the jerk you're seeing is either in what you gave to Compressor, or in how you're playing the Compressor product.

Dennis Couzin
Berlin, Germany
Re: Conform 25fps to 24 or 23.976fps
June 17, 2014 03:25AM
Thanks Dennis - this is working fine for me now in Cinema tools.
The footage was shot at 25fps
There's an extra step involved in exporting the footage from Final Cut as apple prores 422.
That's necessary because cinema tools can't conform footage in the XDCAM codec.

But once that's done, Cinema Tools conforms it instantaneously to 24 or 23.98 fps.
Re: Conform 25fps to 24 or 23.976fps
June 17, 2014 09:15PM
Andy, sorry I overlooked some details. XDCAM is based on MPEG-2 which is based on codec H.262 (for picture). Codec H.262 involves interframe compression.

Cinema Tools won't conform an XDCAM .mov file. Cinema Tools reports that the video has "temporal compression" and is not conformable for this reason. But interframe compression in a .mov file should not, in itself, preclude conforming. QT Edit will conform an XDCAM .mov file. It will also conform H.261, H.263, H264, and other interframe compressed .mov files. It modifies a few bits in the .mov file's metadata and it works.

The .mov file your Sony plugin made from your XDCAM file is probably conformable in QT Edit.

Dennis Couzin
Berlin, Germany
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