2.0 or 3.0 for soundtracks without dialogue?

[bke1138]

Hi all,

First off, thanks to Carl and everyone else who has contributed to this brilliant software. I'm the technical director for a small film festival and making DCPs wouldn't be possible without DoM.

I am curious if there is any advantage to creating a 3.0 DCP using the mid-side decoder for films that just have stereo music without any dialogue? I have made several 3.0 DCPs already with the mid-side decoder creating the center channel that sound good in the theater, but as others have noted, I find that there's not as much stereo separation and the center channel seems to dominate the mix.

Any insights are appreciated! And apologies if this has already been posted, but I couldn't find a similar thread in my searches.

thanks!
Ben

[IoannisSyrogiannis]

"Traditionally", music is played on the left and right screen channels. While the dialogue comes out of the center channel of the screen.
I have heard a lot of stereo-turned-5.0-by-copying music videos/DCPs from "of course I can do that, mixers" that sounded to me like cheap volume upgrades. Being "cheap" both in cost and results.

Your post makes me wonder if the creators of the shorts are aware of and have green-lighted your enhancement with adding center channel. If not, even if I am definitely for, using the center channel for dialogue, I find it a terribly bad idea/policy.

[bke1138]

Thanks for the reply. Perhaps I should give a bit more background. Based on what projectionists have told me and what I've read here, certain Dolby processors will create a center channel from 2.0 content anyhow, so I'm wondering what will give better results: creating a 3.0 DCP using DoM's mid-side decoder or creating a 2.0 DCP and letting the Dolby processor create the center channel?

thanks,
Ben

[Carsten]

It's true that some cinema processors are able to perform matrix decoding and create a center channel during playback. However, it needs to be activated explicitly, it will never do that automatically. And, while many cinemaprocessors have that capability, they are most often not set up to enable this functionality. So, when screening an L/R only DCP in a specific cinema, and with a capable projectionist that has the skills to enable this, it will work, but not in general. So, it's better to create the L/C/R already on the DCP level and distribute the DCP as a 5.1 DCP (with channels 4-6 containing silence).

- Carsten

[IoannisSyrogiannis]

I knew about that being true on Q-SYS processors for cinema. I also knew about that on some Dolby, being a choice on non-sync, AES3 2ch BNC, HDMI and microphones.
It interests me, though, as it would save me from a lot of headaches. Which are the Dolby processors that do that on the signal they get from the Media Block?

[bke1138]

Hi Carsten,

Ah, that's helpful to know. Thanks for the insights.

So even for films with stereo soundtracks that are purely music without any dialogue, you'd recommend creating a center channel from the stereo mix at the DCP level?

thanks!
Ben

[Carsten]

If it's only music, no dialogue, you could leave it at L/R only.

Basically, it's about dialogue intelligibility and speaker recognition. Doesn't apply to music.


@Ioannis - I know that the CP750 can do it, our AP20 can do it, and I think USL JSD-60/80/100, and yes, on an incoming AES-pair.

Don't know for CP 850/950.

[IoannisSyrogiannis]

The CP750 has an option on Decode Mode for Pro Logic and Pro Logic II, but I would expect that there should be Lt and Rt for that to work.
The AP20 is a more serious machine (as was the XD10P, in my eyes). So, even though I haven't been digging into Matrix for digital cinema audio, it seems there is a choice on the configuration.
Have you, or anyone that reads that, tried that with a 2.0 DCP (even a six channel one)?

The CP950 does not interfere with digital cinema input. It does with everything else.
Yet, I would encourage 2.0 to 5.1 on CP750, if there were ethernet/serial commands to support the chance. There are for changing decoding from 5.1 to 7.1 and back, but I have never seen any for Pro Logic. I wouldn't leave that to random people to randomly remember or not to change it.
The CP750.sys.pcm_2_channel_decode_mode serial command seems to me to concern AES3 2ch.
I will definitely investigate at first chance. If only it could up-mix 2.0 to 2.1, it would be a system savior.

[bke1138]

Hey guys,

Thanks for the advice and insights. I realize that most of what I have read about this assumes that the film has dialogue. For the edge cases that are without dialogue and just music, it's good to know that creating a 2.0 DCP is the way to go.

thanks!
Ben

[Carsten]

@Ioannis: The CP750 has two separate decode_mode commands. As far as I know, most cinema processors received the matrix decoding option in later software updates. We don't use a CP750, so my knowledge is from forum discussions and reading the v5 manual.