DCP/MXF Projection issues: Sound is pitched down

Question

Hi,

I've recently finished a theatre-mix, which I delivered as a stereo wav-file at 48 kHz/24bit. The film was shot on a RED at 4K 25 fps. Protools was also at 48 khz/25fps and everything was fine in the studio during playback and recording. Today the director had a test viewing at a local cinema and unfortunately everything sound pitched down.

At the postcompany, responsible for creating the MXF files, they've checked framerates etc and everything is runs fine at their end. I must admit I don't have any experienced with Digital Cinema Package (DCP) and MXF-files. First thing I checked was the framerate and samplerate, which are fine also.

We are a bit clueless.. What could be the problem? Could it be an issue at the cinema?

UPDATE: first of all thanks all for the responses, great to hear from you! The DCP house has checked the soundtrack again today and described it differently than the director (to add to the confusion :) But the projector at the venue is able to play 25fps files, so that's not the issue. The dcp house is researching the issue further, so for now there is not a lot I can do. I have told them that I can provide a pitched version for 24fps playback if necessary. So thanks for those tips guys, really appreciate it!

UPDATE 2: checked the new DCP file and everything was fine. except for a terribly loud hum (50Hz) in the actual screening room. technician didn't hear it but dared to guarantee that it was not a problem. yeah right. how i'd love to know how cinema routing/setup worked... i've been dissapointed so many times already :) oh and it turns out the post company made a mistake somewhere between splitting channels and rendering the audio for the mxf.

Arnoud

Answer 1

If it sounds like a 4% difference it's possibly running at NTSC speed. If it's more in the .1% range that could be film speed rather than PAL speed. Here are some resample rates to help:

50,050 - 01% Up, 4.1667% Up (NTSC to PAL, film-style) 50,000 - 4.1667% Up (Film to PAL) 48,048 - 0.1% Up (NTSC to Film) 47,952 - 0.1% Down (Film to NTSC) 46,080 - 4% Down (PAL to Film) 46,034 - 4% Down, 01% Down (PAL to NTSC, film-style)

Answer 2

AFAIK DCP spec is to run at 24fps - I dont think you can author a 25fps DCP. I've done a few and they all had to be made to 24fps which would explain the slow down.

Answer 3

I'm going to echo people on the pull/up pull/down idea. A producer I was recently working with was trying to decide whether to convert his PAL project to 24 for the DCP. After talking with the company that would be converting to DCP for him, he found out that only about 80% of the projectors out there can play 25fps. So, he went with 24. That meant we had to make the necessary pull-down and post process pitch correction before handing it over for the DCP.

If you delivered for a project at a rate of 25fps, it's possible the DCP house did the pull-down without a pitch correction. I suppose it's also possible that you've got a 25fps DCP that's simply being played back at the wrong speed by a projector that falls into the 20% that can't handle it.

Answer 4

You need to time-stretch your final audio (I use Waves SoundShifter) by 4% in order to match the picture. If you leave it to the DCP production house, they will either slow it down (pitching it down as well) - as in your case, or worse - leave the audio at 25fps and everything will be out of sync. I have converted a fair amount of shows to DCP originally shot at 25fps. Everything had to be time-stretched to 24fps. While in theory the DCP spec supports 25fps, none of the cinemas I know are capable of handling it. So it has to be 24fps, unless you are specifically asked for another framerate (such as 25fps).