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Author
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Topic: CP650 non-syc cross fade possibilities
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Frank Angel
Film God
Posts: 5305
From: Brooklyn NY USA
Registered: Dec 1999
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posted 11-18-2012 08:16 AM
Our policy has always been to program non-sync preshow music for a specific length of time and then start it so that it ends exactly at show-time. In other words, a preshow is program is created (usually from film soundtracks, lots of times from the film on the program) that has a running time of say 29min. For a movie showtime listed as 8pm, we start the CD program at 7:31pm. It ends exactly when the show should start.
In two of our theatres the output of the processor is fed into a multi-channel mixer with the non-sync CD players having their own separate input channels and processed, in one house using a Fosgate ProLogic processor so it can extract surround ambient sound to fill the auditorium with a more immersive 360 degree soundfield. In the other theatre we use a Sansui Quadraphonic QS decoder to get the surround channels extracted for the same surround effect.
Since the non-sync has its own channels which can remain live along with the film channel inputs, for presentation purposes it is possible to be able to end the non-sync music EXACTLY as the show first frames hits the screen. In fact I like to let the very last strains of the preshow music slightly overlap the start of the film, usually a Warner Brother's cartoon. The movie opening sound can step over the last strains of the preshow music. It creates a very tight, integrated effect having whatever music selection is playing to actually end "on purpose" rather than just fade out in the middle of a cut or worse, simple get popped off at any place it happens to be playing as I have heard done in many places.
In one theatre however, there is no mixer inteface -- the CP650 goes directly to the house amps. Question is; is there a way for the CP650 to allow the both the film sound AND the non-sync to play together rather than either/or, other than having to add a mixer between the processor and the amps? Not that that would be such a terrible thing, but it just adds a whole other issue of putting the output levels of a processor that has been B-channel aligned at risk by those who when they see a mixer, can't seem to resist the temptation to fiddle with all the dials. In the places where we do have this mixer setup, I have always said the mixer should be dipped in carbonite once every thins is properly aligned.
Anyway, can the CP650 be told to leave non-sync input live when film is selected?
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Harold Hallikainen
Jedi Master Film Handler
Posts: 906
From: Denver, CO, USA
Registered: Aug 2009
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posted 11-18-2012 02:57 PM
You raise some interesting points, so I'd like to discuss them further (without answering your question!).
A fair amount of the complexity (and cost) of a cinema processor is handling all the various inputs. For analog inputs, there are differential input amplifiers, variable gain amplifiers, and analog to digital converters. Each ADC uses more DSP ports (or could be switched before the DSP, but this eliminates the mixing you're describing). Additional two channel digital inputs (SPDIF and TOSLINK) also add complexity and cost. But, at least we don't now have to have the photocell inputs for film!
Anyway, it SEEMS that the entire show, including preshow music, could just be built as a series of DCPs, just as the trailers and main feature are. Then, everything would play off the server, and only the AES/EBU input on the processor would typically be used. This would require conversion of all content to DCPs for ingest.
PERHAPS a cinema audio processor could have three inputs: 16 channel AES/EBU, microphone (typically for emergency use), and an HDMI pass-through for streaming live content. I'd be interested in hearing comments on this idea. Could all "normal" show content (preshow music, advertising, trailers, feature, etc.) just be a series of DCPs handled by the server?
The original post asked about crossfade between the NS and AES/EBU input. The "series of DCPs" idea above would not allow this since content is just played sequentially. Back when I was in radio, we used tape based automation systems. Each piece of content had an End Of Message cue (150Hz on tape cartridge, 25Hz on reel to reel tape). The next source would start at the beginning of the cue and the current source would be turned off at the end of the cue. This allowed the crossfades. During dub to tape, the cue would be placed where the content faded so the next piece of content could be over it. If a piece of content ended suddenly, the cue was placed after that sudden end.
Anyway, back at cinema, during trailer playout, we do not have any audio crossfade between trailers. Sometimes there's even a few frames of black inserted. In recent ISDCF HFR discussions, it appears the goal is to play the trailers with no gaps (possibly up-converting to the highest frame rate in the trailer string and converting 2D trailers to 3D by sending each frame to both eyes), but then changing settings such that the feature always played in its native format (no frame rate upconversion, etc.). The switch may take a second or two, and during this time the screen is black and the audio is silent. This seems acceptable to me. It's like a dramatic pause. Something big is coming. We really don't want it to be right up against the last trailer.
So... does the same thing apply to preshow music? Do we really want to crossfade from preshow music into the first trailer? I agree that we should not just fade out of the middle of a song, but that can be prevented by building the preshow music DCP so that it ends properly.
So, I look forward to comments!
Harold
Design Team Member
USL JSD-80, JSD-100, JSD-60
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