DCP projector plays only center audio channel in a theater

[Keimo24]

Hi!

We encountered this very odd problem when we were doing our test screening at the local film theater. It seems that only the center channel works in our DCP copy. The odd part is, everything sounds fine on DCP-o-matic player (and on other brands as well). Every channel works just like they should at home but not in the theater.

We have done some tests and the only difference we have found is that when we exported a file from DaVinci Resolve (.mov) with "render one track per channel", DCP-o-matic does not automatically assign channels but you have to do it manually. When "render one track..." box is unchecked DCP-o-matic can assign those channels automatically. Also when listening to exported .mov-video from Resolve, at least VLC-player doesn't play all channels when "render one track..." is checked.

It sounds like that the "render one track..." checkbox is the problem, but why would DCP copy work at home perfectly either way? Is there some way that those multiple mono files still haunt somewhere in the DCP copy and mess up with the projector but not with home players? We have no way to test this at the theater before our screening.

Any help would be greatly appreciated!

[carl]

It might be interesting to load the audio MXF file from your DCP (the smaller one) into something like Audacity. Then we could see the waveforms, and it might give a clue.

[Keimo24]

The waveform looks normal in Resolve and everything sounds fine. Here is the Metadata file

[carl]

You mean the waveform of the MXF file, reimported into Resolve?

[Keimo24]

Yes, DCP Audio reimported to resolve.

[Carsten]

What do you mean with 'the waveform looks normal'?

I suggest you load the MXF of the DCP you took to the cinema into Audacity (install Audacity + the FFMPEG plugin). Then upload a screenshot of the Audacity window here so we can have a look.

It is not impossible that something is broken in the cinema, or that incompetent staff was helping you with the screening. As long as a dialogue channel is audible, a general audience may not even complain about missing other channels.

However, I think you used the 'one stream per channel' mapping for your source file, but that will deliver only once channel into your DCP without special adjustments.

You need to make yourself familiar with the difference between audio stream and audio channel. You can use both audio stream/channel types in DCP-o-matic successfully, but you need to understand the difference and set the audio matrix accordingly.


- Carsten

[Keimo24]

I put the mxf file into Audacity and here is the screenshots:

[Carsten]

That looks correct. Are you sure you are only hearing the center in the theater? If the center is dominant, it is sometimes difficult to recognize the other speakers. I see that in the middle of the waveform, there is a section where there is nothing in center, but in L and R. That should be easy to notice.

Anyway - if this is in your DCPs audio MXF, then L and R must be audible. LFE and surrounds are probably too soft to be clearly recognised in the full mix.

Again, it would be quite unusual, but it wouldn't surprise me if amps or speakers had been off or defective during your test. There are official Test-DCPs (e.g. from Dolby), that play test sounds through all speakers, so that it is easy to tell if all systems are working. In commercial/standard movies and trailers, there is mostly dialogue and 'some' music in the center channel. It may actually run unnoticed for some time if the other speakers are dead/off. Unlike the center channel - if that fails, you have complaints immediately because of the missing dialogue.

[Ryan Gallagher]

I agree this sounds like a single-track vs multi-track DCP authoring issue. Cinemas want multi-track DCPs, 8 or 16 typically. VLC and others want single-track audio with the channels packaged within (generally). DCP-o-Matic player will probably sound the same with either DCP if you are previewing in stereo.

If you rule that out, and have a true multi-track DCP with audio active on each channel (you can toggle them all off and back on individually to determine that), then move on to the cinema troubleshooting:

Have them play something with "known good" surround data in your same format (5.1, 7.1 etc).

On your content, Do the independent channel level meters also not move on whatever processor is installed in the cinema?

If you have meters moving at the processor but don't "hear" it, that sounds like the problem is elsewhere, after the processor, in the room EQ, or in the soundtrack Mix perhaps. Most processors let you monitor individual channels in the booth too (depending how they have set it up). Would be a quick way to confirm you have some activity on non-center channels.

[Carsten]

DCPs do not carry multi-track vs. multi-stream properties. The DCP MXF audio format only carries multiple-tracks in one stream per file properties.
Multiple streams as in MP4/MKV, etc. consumer formats for different language audio are enabled for DCPs in the form of version files.

It's not the DCP that matters here, but the source file handling prior or during the conversion to the audio MXF. If the DCP carries 6 audio channels, they have to be audible in the cinema, otherwise something is dead, defective, or switched off or misconfigured.