11 Aug
2014
11 Aug
'14
3:42 p.m.
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:
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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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