On Sat, 9 Aug 2014, lilian lefranc wrote:

There are two ways to slow down the sound with a factor 25/24: change the tempo or change the speed.
Change the tempo will try to keep the pitch but need a complex algorithm to do it with good results (the best one is dirac, available with time factory). Change the speed will change the pitch and the tonality of the voices and music. Not really suitable in terms of production and clearly audible. But it is the solution that is used in many labs.
ffmpeg has a very bad algorithm (atempo) to change the tempo and I did not find a way to change the audio speed.
You can use sox with the speed option.
I don't know how is doing dcpomatic, so I change the speed of the sound before with sox, and the speed of the video with ffmpeg to provide dcpomatic a 24 fps source.

DCP-o-matic changes the speed: it re-samples the audio and then runs it fast or slow.  See:

http://dcpomatic.com/manual/html/ch09.html#idp325888

Cheers
Carl

Lilian

Le 09/08/2014 00:39, Carsten Kurz a écrit :

Am 08.08.2014 um 23:29 schrieb Ben Edwards:

Hi, I just discovered the source material is 25fps, was planing on making a 24fps DCP I beleve some ceinmas do not support  25?  is this correct or should I create a 25ftp DCP.

How good is DCPOMsatic at doing frame rate conversion?  I am sure it is great but thought it better to ask.

Ben, you're learning it the hard way - formally, 25fps is not supported in Interop DCPs. It may work on some systems, but I have no idea how often it will fail.

Dolbys DSS100/DSP100 does not support 25fps with DCP content, not in Interop, not in SMPTE format.

Most digital labs/companies slow down 25fps features to 24fps, as Carl explains. If you choose 24fps DCP with 25fps content, dcp-o-matic does all the necessary steps for you.

- Carsten





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