Dolby Film Encoder??

[Bokir]

All,

I understand that we can use either Dolby SEU-4&SDU-4 Combo or the Dolby TDM plugin for film pre-dub monitoring, but shouldn't used it for final encoding. The Dolby people will later supply their Film Encoder on the final day of the mix.

My Question:
1. Can anybody explain what makes the Film Encoder different then either SEU-4/Dolby TDM?
2. What really happen if we send an SEU-4/Dolby TDM encoded sound for film sound? In which part/area it will be decoded wrongly?
3. Is there any trick to emulate the "Film Encoder" with Dolby TDM?

Sorry for my english. Any response will be appreciated. Many thanks.

[Joe Barnett]

If you going to deliver SRD, then Dolby has to be there to encode the bitstream to MO.

If your delivery is only LT/RT then using the plugin is very similar to the the seu 4. In some ways the plugin in my opinion is actually superior with regard to alignment and steering. Older models of the hardware encoders have auto-gain functions which while they keep center material center, can have deletirious effects on panning.

The newest Dolby box, the DMU, is superior in all aspects. I can't say enough good things about it.

When you don't use Dolby you miss several very important things:

1. Dolby has a wonderful container to limit peaks. It's a compressor limiter package that sounds very good.

2. They also have an optical simulator to hear what those crunchy explosions at 200% modulation are really going to sound like coming of the optical reader in the theater.

3. Just as important is the Dolby name on the printmaster. Their seal of approval on your mix insulates you the mixer and the facility from technical issues down the road. If the lab shoots the negative poorly and it sounds awful and they have already made 3000 prints it's not your fault, Dolby approved the mix!

Hope this helps.

[Branko]

Joe made some good points and practical advices in his reply and I'll add just one more:
DS-IV encoder is only a part of a complex studio setup used to produce soundtracks for theatrical release. It is closely linked to Cinema Processor, and together with it provides not only encoding, but also metering, proper monitoring levels and appropriate room equilisation. All these things are essential in production of correct mixing stems and print masters.
Branko

[Bokir]

All,

Thanks Joe and Branko for your response. My appologize for not being specific and clear on my question. Please allow me to re-wrote my question.

My question is solely about doing analog print. No option for Dolby Digital here, and it's because most of our market is not there for the extra budget. They're doing video to film (kinetransferred) stuff and happy with just stereo print.

I mix in a rather small room 6m x 4m x 2.75m with 5.1 setup. I calibrate the room to OVU = -20dBFS = 85dBC on each of the front channel (LCR), and 82dBC on each surround channel. I eq the room for flat response, following Dolby guidelines. And on the way to the optical transfer, I have asked the lab to encode the final mix through Dolby 363 SR/A (in A mode).

I have been mixing for several film now, but my concern is, when we screened the film print--the result is not always as we expected.

Most common is, too much mid-hi frequency (horn related), no mid bass (however sometimes I could hear the subs sounds quite the same to my mix room), and sometimes the surround sound louder then the main channel.

That is why I'm seeking for any of your assistant to understand this behaviour better.

My question is:

- If I do the monitoring through Dolby TDM (and mixed and pan accordingly), will the imaging (stereo and surround wise) on the final print be the same when processed through Dolby Cinema Processors?

- Should I lower the surround level on the Dolby TDM decoder?

- Is there any eq or dynamic adjustment issue I should consider? I have used TC MasterX: default preset, smiley target, very light compression (-4 reduction), and -6 output. All in hope for tighter dynamic and increased low and high freq response.

- What should I know about optical print limitation (I don't have optical simulator)? I do limit my final print to -6 dBFS though.

Any insight will be appreciated. Thanks.

[dr sound]

Bokir,
A couple of thoughts. How about lowering your monitor level to 82 or 80spl. Who calibrated your room? When you say you made it flat to the Dolby guidelines, please elaborate. How did you calibrate your sub. When you take your mix to anotheer room, do you know how that room is calibrated? Do all films played back in that room sound stange to you, or only things you've mixed?

[Branko]

Bokir,
In my opinion, there are many ways to achieve good results without all the fancy equipment that costs a lot of money your clients aren't ready to pay, but one thing is essential:
the monitoring. Listening through a propper monitoring can reveal those weak points in your signal processing chain. By rule, in the case of mixing for theatrical release, your work will be played back through some Dolby Cinema Processor, which leads to a conclusion that you should use the same device to evaluate your mixes.
On your website, I've seen you've got MK monitors, which is maybe the best thing you can buy on the market. When you calibrate the room, you should consider various important things, like speaker position (in a cinema theatre, they're always behind a perforated screen), mixer's distance from speakers, surround distance and positioning and level/frequency response of the system. FLAT for Dolby means flat from 40Hz to 2KHz and 3 dB per octave roll-off above 2 kHz. This EQ is known as "X-curve" and applies to reverberant, room response. You say your mixes contain a lot of upper midrange - is that something above 2-2.5KHz? Using MasterX "smile" curve does exactly that - cuts in lower mid and boosts highs and lows.
Try to get some DA88 print masters of films you've heard in a theatre and play them back in your room, and compare to your mixes - you'll surely draw some conclusions.
Optical recorders are calibrated at 50% modulation for Dolby Level. This leaves some 6-8 dB of headroom, and with 3db centre loss and 3 db SR loss gives a total of 12-14 dB of headroom, which means you've got your limiters right.
Branko

[Bokir]

Many thanks to you Marti & Branko.

About my room eq, I do set the room for 'real' flat: white noise, slow, 85dBC main, 82dBC surround , and 82dBC LFE (band limited noise).

When I reffering to Dolby guidelines what I really mean is the Dolby stated that "If you mixed in small room--eq flat, whereas you mixed in theatrical sized dubbing stage you should eq x-curve". Is this still valid?

About lowering to 82dB, I do lower my master fader to -5 while mixing and put it in full only for checking the noise level and presentation (when the client asking for MORE!!). Will that make any different?

I do have a final mix copy (in PT files) of what we've mixed in a real dubbing stage (Dolby and THX certified room) in Sydney-Australia. And I do reffer to it from time to time.
However those mix are already Dolby Matrixed (prior to SR).

Just to clarify, I started to use the masterx (smiley with mid-high dip) after the mid-high problem (yes it's around that 2-3KHz) trying to compensate for that. But I only get some rather satisfying results after I add around 5dB boost on the low and 3dB on the top high. But this is very unpredictable.

Will I be better if I eq my room x-curve? But my room is small and not much reverberant?

MORE QUESTION:
Does that matrix encoder do something different (in eq or dynamic processing) then what the Dolby TDM does?

Also I recalled when we do mixing in the dub stage the guy used "dbx subharmonic" to add some boom (subs). Is this really necessary?

Sorry for making this complicated. I'm learning everyday. Thanks for the support.

[Branko]

Bokir,
First, to answer your questions, I don't think TDM is doing anything different from hardware (DS - IV) when encoding itself is concerned. I'd say it really misses some "optical sound - specific" features that can be found in Hardware version, like metering, which is calibrated to correspond to optical recorder modulation and "container card" limiter, which is a 4 ch. 5-band clipper. This device excludes the possibility of "optical crash" in the recorder, while keeping the levels high.
Coming back to original issue (and your problem of producing unpredictable results in yor studio), it is important to stress that the whole concept of Dolby cibema sound is based arround IDENTICAL (well, almost identical) LISTENING CONDITIONS in both mixing studio and theatre. Try to talk to Dolby representant in your country and get a Dolby Sound Consultant to help you calibrate your room.
Branko

[Bokir]

Originally posted by Branko:
Bokir,
First, to answer your questions, I don't think TDM is doing anything different from hardware (DS - IV) when encoding itself is concerned. I'd say it really misses some "optical sound - specific" features that can be found in Hardware version, like metering, which is calibrated to correspond to optical recorder modulation and "container card" limiter, which is a 4 ch. 5-band clipper. This device excludes the possibility of "optical crash" in the recorder, while keeping the levels high.

This is exactly the explanation I'm looking.

Originally posted by Branko:
...it is important to stress that the whole concept of Dolby Cinema sound is based arround IDENTICAL (well, almost identical) LISTENING CONDITIONS in both mixing studio and theatre. Try to talk to Dolby representant in your country and get a Dolby Sound Consultant to help you calibrate your room.
Branko

Thank you for reminding me about this issue.

[John McDaniel]

Originally posted by Joe Barnett:
The newest Dolby box, the DMU, is superior in all aspects. I can't say enough good things about it.

I supervised a transfer of one of my mixes recently as it went from PT, through a DFC and into a DMU (my first time to Dolby Digital for release print) and I'm wondering...

are the inputs to the DMU analog only or does it accept digital signals as well? Just curious.

thanks, j mcd