Making a DCP from a Blu-Ray with only L-R sound

[Mike Babb]

@mike your Ovation2 can have a button which will take in DCP 2.0 and upmix it in the case of stereo or LtRt tracks. For a dual mono track it will route to the center channel.
I will also add that the ability to do that came from a suggestion made here on F-T years ago, we added it to the last version of Ov1 software too.

[Antti Näyhä]

Is there a low cost prologic style up mixer that would convert a L/R to 5.1 before encoding with DCP Matic?

Waves UM225 / UM226 is pretty cheap, and better than the open-source SoX (at least the last time I compared them).

UM225 outputs 5.0 and UM226 gives you 5.1. I find UM226's LFE output a bit unpredictable: to get balanced bass, you'd really need to adjust the LFE manually while monitoring on a properly calibrated cinema system.

I tend to only use UM225 with "Mode 4" and gain decreased enough to avoid any clipping, all other settings left at defaults. I find the result not that far from hardware Pro Logic decoding. Granted, it's kind of a conservative and center-heavy upmix – but it's also pretty much idiot proof, and I like getting a perfectly usable upmix every time, even without monitoring in 5.1.

There are, of course, better (and much more expensive) tools such as Penteo or Nugen Halo. I'd definitely look into those if I was an audio professional doing actual upmixing, as opposed to a lowly projectionist just trying to make 2.0 material sound tolerable in a cinema setting.

[Brad Miller]

It would be nice if Dolby would simply release their own "Pro Logic decode to 5.1" software. What's ridiculous is they could write the program, charge whatever (something reasonable though) and just keep selling it. It's not like the decoding needs to change.

[Steve Guttag]

Release it where?

[Jesse Crooks]

The problem is that it's difficult to use in a show situation. Because the CP750 won't let you create multiple macros/presets - there is only one for the 8-channel AES input - if you're playing a mono or 2.0 CPL that you want to put through the ProLogic decoder that is in the same SPL as regular 5.1 or 7.1 content, you would either need to pause the show, connect to the CP750 using its app, change the processing method, then restart; or insert automation cues into the SPL that send the CP750 an API command to change the decoding method during the show. The latter is more feasible, but in arthouses and screening rooms that use little if any automation (i.e. the sort of place that would likely be playing a 1.0 or 2.0 DCP and want to use this feature), the chances are high that the projectionist won't know how to do it, and the tech won't be able to leave them with a "one push" solution for doing so (unless the room has an integration front end, e.g. Crestron or AMX).

At my four arthouse theaters we always use a cue to transition from 5.1 preshow material to 2.0 features. No idea why this would be a problem for anyone.

[Gordon McLeod]

At my four arthouse theaters we always use a cue to transition from 5.1 preshow material to 2.0 features. No idea why this would be a problem for anyone.

The problem is that the 2 channel audio is actually the LtRt tracks for matrix 4 channel. As such there is a hole in the middle of sound field which leaves dialogue floating depending on your seat

[Ryan K Georgieff]

At my four arthouse theaters we always use a cue to transition from 5.1 preshow material to 2.0 features. No idea why this would be a problem for anyone.

Why do you need a cue? Doesn't the CP just kick in the decoder? At least the CP500 ha have just sucks in what you throw at it and plays it. I have had stereo and 5.1 on the same Playlist without worries. Maybe the cp500 is a true beast and those after it are weaker? Hearing what the cp950 Doesn't come with makes me sad.

[Steve Guttag]

What are you going on about? The CP500 does NOT just kick in a decoder. And from DCP, presuming you are using its analog external 6-channel input (with the option card) it just puts out what you put in. If your DCP is 2-channel, then you get just Left and Right...just like any other processor. You CAN create a pro-logic decoder format on the CP500 but you are still having to cue it manually. About the only thing it could do automatically was for film to jump to format 10 for Dolby Digital movies and if that faulted out it would fall back to SR (and those had to be configured).

It is certainly possible, with a processor like Q-SYS to have it monitor the channel activity and decide if the source is just 2-channel and automatically decode that but you'd want to ensure that it wasn't so trigger happy that it falsely switches. I could also, probably have it look at the CPL name and parse out the channel configuration, if the author properly named it to select the right channel format...but the CP500 would never be able to do that.

I'm surprised that Dolby doesn't do some internal communication with their own IMS3000 to offer an auto format selection. Then again, I'm very surprised, in this day and age, that DCP metadata isn't automatically selection the right picture and sound formats.

[Brad Miller]

Release it where?

As a stand-alone Windows program, etc.

[Marcel Birgelen]

I'm surprised that Dolby doesn't do some internal communication with their own IMS3000 to offer an auto format selection. Then again, I'm very surprised, in this day and age, that DCP metadata isn't automatically selection the right picture and sound formats.

I've been wondering about that for years now. It can't be that difficult to encode basic stuff like available sound formats, aspect ratios, etc. into some metadata structure and make it a mandatory part for all DCP releases after a certain date, all other modern media formats seem to be capable of doing so, but DCP needs to revert to an archaic, non-enforced and therefore often labeling system, even worse: sometimes DCPs are just labeled wrong... You should be able to put this metadata in there, without breaking backward compatibility. The only new potential can of worms you're opening up with this is that "projectionists" / "show programmers" will get even more lazy and forget that there will then be a "legacy" catalogue of about 15+ years of DCPs that don't have this kind of metadata and where manual programming of format cues is still necessary.

[Steve Guttag]

Brad, anyone could do that...not just Dolby. QSC did that within Q-SYS even. Whatever patents on the prologic decoder are long since expired as are the "modified "B" decoder. Do you really think there is a market for a standalone software prologic decoder? And, lets face it, if DCP O MATIC had such a decoder, would this conversation even exist? I'm not sure what their upmixer is doing to give the results in a hodge-podge manner but one would think that there is a suitable "figured out" decoder out there. I'd prefer it to be part of the authoring program to ensure that latency isn't introduced by having a 3rd party program decoding the audio and then re-syncing that up with the picture.

[Carsten Kurz]

A matrix decoder is different from an upmixer. Very few people request matrix decoders for DCP-o-matic. Many would love an upmixer (as e.g. Neo:6). A decoder needs material that has been encoded for surround, that is Lt/Rt stereo tracks.. An upmixer will upmix any stereo (or even mono) content. There was a software Neo:6 implementation available for a time, bundled with some sound cards, and there are a few plugins available for common audio processing software. But there are no (decent) open source implementations to my knowledge. A good upmixer is way more complicated than a matrix decoder.

[Gordon McLeod]

A matrix decoder is different from an upmixer. Very few people request matrix decoders for DCP-o-matic. Many would love an upmixer (as e.g. Neo:6). A decoder needs material that has been encoded for surround, that is Lt/Rt stereo tracks.. An upmixer will upmix any stereo (or even mono) content. There was a software Neo:6 implementation available for a time, bundled with some sound cards, and there are a few plugins available for common audio processing software. But there are no (decent) open source implementations to my knowledge. A good upmixer is way more complicated than a matrix decoder.

Almost all dvds with 2 channels of audio only they are the LTRT tracks or a mono track on both channels

[Steve Guttag]

Carsten,

There are way more desires for a matrix decoder for DOM than you may realize. None of my clients have ever requested an upmixer...they do want a matrix decoder (almost without exception). They don't want a 2-channel source to play out of just left and right as it sounds incredibly hollow in a cinema where those speakers are VERY far apart.

[Brad Miller]

Carsten,

There are way more desires for a matrix decoder for DOM than you may realize. None of my clients have ever requested an upmixer...they do want a matrix decoder (almost without exception). They don't want a 2-channel source to play out of just left and right as it sounds incredibly hollow in a cinema where those speakers are VERY far apart.

I agree, most people using DOM want a proper pro-logic matrix decoder than any sort of fake upmixer. There are 2 decoders in DOM and one of them was done basically as I described and works reasonably well, but is only for front channels (everything mono goes to center, everything left only goes to left, everything right only goes to right). The other 5.1 mixer is a disaster and sounds terrible. I believe it was done by working off of frequencies or something, but it should be dumped. If that front side mixer would simply then take all out of phase audio between Lt and Rt and send to both surround channels as I originally explained, they would have a pretty decent decoder for DOM.

But still, for Dolby to not simply have a Windows program that people can drop an LtRt wav file into and it simply convert to a 5.1 wav file via pro-logic is silly. It would be used a lot more than anyone at Dolby realizes.