Help with Dolby Digital 5.1 Encoding & playback for Cinema

[Ciaran]

I am trying to find the best method for attaching the movie audio that I mix onto the final image for my clients. So far, for TV, they have always wanted an LtRt mix, however with independent films that has been a different story.

Generally speaking, my movie audio mix gets placed onto a digibeta tape, and thus far, it has been an LtRt mix on the first two channels, and a Dolby Digital mix onto the second channel pair.

Question 1:
Is this the best method (LtRt and Dolby Digital 5.1 ac3 file on the 4 channels) to lock the final information onto a digibeta for these film makers, or is there something I am naively missing. These digibeta's often end up being the master tape, the source of DVD duplications, and the actual screening copys in cineplexes at film-festivals and agency screenings.

I have recently been told Dolby E might be a better encoding, but up until now, even some plugin manufacturers have suggested it is best suited for "Broadcast" and not for cinema distribution. I have had no direct answer from anyone as to what encoding on a digibeta tape is best for playback at cineplex's.

As I mentioned, most of the independent movies I work on are going to festivals and screenings, but I don't know are these screening situations any different to actual finished movies that get cinema distribution - in the sense that, is there any difference in how a non-film-reel based movie get distributed or played back in a cinema? How does the cinema receive their copies?

Question 2:
My second question is specifically regarding the dolby encoding for cinema. As you know, when encoding Dolby Digital, there are many settings options available to change. I am a bit concerned that I should not be sending mixes to digibeta with Dynamic Range Control available, although I think it should be there for home DVD distribution. My problem has been that, mixing at 85dB and bringing those mixes to cinemas that should be at 85dB should theoretically ensure that whatever is perceptively "loud" in my mixing environment should be equally perceptively loud in the cinema environment, but often this does not prove to be the case. So, I am wondering if it might be my encoding that is the issue, or if there is something else I should be looking at?

Any help or feedback on these issues would me much appreciated.

[JR Fountain]

I was just thinking of posting a question very similar to your first question. I'm soon to start working on an independent feature doc that will be playing at festivals. I'd like to do a 5.1 mix for it but was under the impression that only an HD master would be able to accomodate the 6 tracks. The film was shot in DV and so it doesn't make sense to up convert it if I can encode a 5.1 mix to two tracks of a D-Beta. Can anybody shed some light on this?

Thanks,
JR

[JR Fountain]

Hey Ciaran,

Well I decided to just call Dolby and found that for D-Beta you can basically only put an LtRt on it for cinema playback. Unfortunately the CP650 and the DMA8 do not decode Dolby E. Dolby E seems to be exclusively for broadcast. You can however encode a Dolby Digital bitstream onto an HDCam tape much like you do for a 35mm film print but you will have to also pay for the Dolby licensing as well. The film I'm working on doesn't have that kind of budget. I didn't ask but am quite sure that the cinema processors will not be able to decode AC3 files, those are for DVD authoring. So it looks like what you're doing is the way to go, LtRt for festival screenings/broadcast, and AC3 files for DVDs.

Hope that helps,

JR

[georgia]

DOLBY AC3 is for Threatre and DVD
DOLBY E is for Broadcast

Place an LtRt Analog mix on 2 tracks of the Digibeta and the AC3 file on the other 2 tracks.

Encoding in Dolby E and Dolby AC3 DO NOT change the playback levels. What goes in gets printed. Levels will change based on the DECODER settings. This is true with set top boxes, DVD players and Cinema Decoders.

Most cinemas still use optical reels, but more and more are going to Digital. Digital Playback is usually via a disk based server, Digibeta, HDcam, HDcam-SR or D5 decks. Indie films also are played in cinemas using DVD on occasion. If the media has an AC3 file its' audio is routed to the decoder and the picture is routed to the digital projector.

Whenever you mix for threatre , mix in a calibrated dub stage. Second, If you are encoding for cinema for film, and you are planning a 5.1 mix you will need to contact Dolby to arrange a Printmastering session. If you use DTS the same is true. If you are going to encode to digital tape you should be using a DOLBY hardware encoder. Printing a Dolby AC3 encoded mix to a digital tape does not require a printmastering session. Remember additionally to the session, you will need to purchase a Dolby license for the threatrical presentation if you printmaster.

If you are working in a properly calibrated and approved room your mixes will translate properly.
What you hear at the listening position will be what you hear in the threatre 2/3 of the way back in the middle of the seat row. ( give or take a row or two ).
That's of course of the threatre isn't screwed up as well.

cheers
geo

[JKD99]

Dolby E is, however, being used more and more for films screened on video (D-Beta, D-5, etc) at film festivals.
It's vital, though, to get a tech check prior to the screening, to ensure that the Dolby E is being decoded properly.

[Ciaran]

Hi JR,
thanks for that info on calling dolby. I was actually thinking of doing that you but you beat me to it! Ha! I'm going to have to call them about the licensing anyway, so I might see what they have to say. Ac3 files are also Dolby E according to the post house that are doing our transfers, and seeing as they've been transfering all the Marvel stuff, I assume they are right.

I still need to find out about the Dolby Digital settings that will work best for Cinema and not just DVD, so I'm holding out hope that someone here has the answer to that.

I'll post any new information that comes my way.

Oh, and Geo, thanks for all that phenomenal info. You certainly loaded me with information I hadn't been privy to, and some that I knew but was doubting myself on! I think my only concern with dolby digital encoding is trying to ensure that I circumvent the encoders doing any compression, especially in the cinema version, so that the compression and dynamic range that I've been mixing towards is correctly translated to the theatre.

Ciaran

[georgia]

http://www.dolby.com/assets/pdf/tech..._it_with_E.pdf
http://www.dolby.com/assets/pdf/tech...2.5.1guide.pdf
http://www.dolby.com/assets/pdf/tech...data.Guide.pdf
http://www.dolby.com/assets/pdf/tech...3_ATSC_err.pdf
http://www.dolby.com/professional/pr.../dp569_01.html


Dolby Ac3 anf Dolby E are not the same thing...

http://www.dolby.com/professional/pr...ns_dolbye.html
http://www.dolby.com/professional/pr...digitaltv.html


cheers
geo

[JR Fountain]

DOLBY AC3 is for Threatre and DVD
DOLBY E is for Broadcast

Thanks for the info Georgia! Just to clarify then, AC3 audio from a D-Beta tape can in fact be decoded properly by the CP650 that is usually found in theatres?

JR

[JKD99]

Not neccessarily. The Dolby Cinema Processor considers anything that is not a film print (ie video or DVD) a "non-sync source".

Not all models of Dolby Cinema processors are able to decode Dolby Digital or Dolby Stereo from non-sync sources, so check in advance. I've found an extremely wide range of processors in various venues, and oddly I've often experienced the opposite of what I'd expect, meaning a smaller film festival like Slamdance had the latest gear and could decode everything just fine, but The American Cinematheque at the Egyptian Theater here in Hollywood had the older style. Go figure.

Hope this helps, good luck!

[pneyrinck]

DOLBY AC3 is for Threatre and DVD
DOLBY E is for Broadcast

Hopefully, I won't make things any confusing here, but AC3 is used in broadcasting. AC3 is widely used by digital television broadcast to the consumer. It is also used for satellite uplink and professional delivery applications. StreamStacker is an example product for the satellite uplink applications. DirecTV's delivery specs call for AC3 delivery on digital video tape.

I would say it this way:

Dolby AC3 (Dolby Digital) is used in theater/cinema, DVD, and broadcasting
Dolby E is used in broadcasting

Paul