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This topic comprises 3 pages: 1 2 3
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Author
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Topic: Couple of dumb D.T.S .questions
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Rick Long
Jedi Master Film Handler
Posts: 759
From: Toronto, Ontario, Canada
Registered: Nov 1999
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posted 06-18-2001 07:46 PM
Ever have someone ask you a seemingly innocent question and have your brain suddenly go into "freeze" mode and be unable to think of a valid answer? Happened to me not once but twice today.I had just finished explaining that with D.T.S., if timecode is lost for a short duration, the unit will "coast" for 4 or 5 seconds. If time-code is re-established during that time, no problem, otherwise it will default to optical. "Does this mean", I was asked, "that if I have two trailers, the first one DTS, and the second one analog, that the first four of five seconds of the analog trailer will be muted until the DTS defaults?" As if this wasn't enough, the smart-ass then asked: "What if a soundtrack score called for a 1KHz note to be played for exactly one second, but the projector was running at, say, 10 % below speed (possible with drive-belt slippage on some older projectors)? Would the note, like on analog be played at 900 Hz, or would we hear the 1KHz note, but at a longer duration?" Would someone please field these for me while I thaw my brain out in the microwave again?
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Adam Martin
I'm not even gonna point out the irony.
Posts: 3686
From: Dallas, TX
Registered: Nov 2000
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posted 06-18-2001 08:00 PM
quote:
"Does this mean", I was asked, "that if I have two trailers, the first one DTS, and the second one analog, that the first four of five seconds of the analog trailer will be muted until the DTS defaults?"
Yes. This drives me nuts, so I usually add some opaque film in between (ie, policy tags) or try to run the analog trailer first. quote:
"What if a soundtrack score called for a 1KHz note to be played for exactly one second, but the projector was running at, say, 10 % below speed (possible with drive-belt slippage on some older projectors)? Would the note, like on analog be played at 900 Hz, or would we hear the 1KHz note, but at a longer duration?"
Never experienced this, but I would guess one of two things would happen. (1) You would not be sending valid timecode to the player and it would not run in digital. (2) You'd get the 1kHz tone and the sound would "skip" like a CD, but maybe without the "click" since DTS has a 5ms cross-fade for timecode jumps.
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Rick Long
Jedi Master Film Handler
Posts: 759
From: Toronto, Ontario, Canada
Registered: Nov 1999
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posted 06-18-2001 09:51 PM
Not sure I agree, Joe. Too often, on an automated system using rotary timers to shut down the show on automation, the non/sync cue switches the Dolby to non/sync, only to have the DTS (talking 2-drive system here) default and switch the Dolby to 04, rewarding the audience with the sound of the tail-piece as it runs through. (Shakes the dust out of the sub-woofers, anyways). If there was a "end of file" flag, surely they would put one at the end of the feature. Also, OK maybe 10 % slow was a little much, but assuming a slight (say 1 %) drop in speed, would the DTS be correcting itself during the whole performance? And how long would that 1kHZ note play?
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Scott Norwood
Film God
Posts: 8146
From: Boston, MA. USA (1774.21 miles northeast of Dallas)
Registered: Jun 99
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posted 06-18-2001 10:40 PM
The end of show problem _is_ an issue. I hate hearing tail leaders run through, and I'm quite sure that it isn't very good for the loudspeakers. Supposedly there is a fix for this.
The trailer issue isn't really a problem, since the first couple of seconds for most trailers is just the ratings band, which doesn't have sound anyway. As long as the fadeout on the previous trailer is there, it's a nonissue unless you have, say, a trailer in DTS spliced right before a non-digital policy trailer or something that doesn't begin with silence. In this case, the workaround is to either add black leader (as suggested) or add an automation cue to switch to format 01/04/05 (as appropriate) to be read before the policy snipe begins. (Obviously, this can all be done manually, too, but I've never worked with DTS in a booth without automation.)
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Bobby Henderson
"Ask me about Trajan."
Posts: 10973
From: Lawton, OK, USA
Registered: Apr 2001
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posted 06-18-2001 11:04 PM
To add a little more to Rick's second question, about what would happen if the projector were running slow, this points out a basic misunderstanding the public has with digital audio.With a fully uncompressed linear digital audio bitstream, you can do DSP tricks to it to cause pitch shifts, slow downs and other stuff like that. You don't really have that capability when dealing with a packeted data compressed format like DTS. The audio pretty much has to play as is. Basically, it either works or doesn't work. If the projector slows down to too slow a rate for the DTS player to maintain proper synch, the audio is just going to pop back and forth between digital and analog failsafe tracks. For dealing with the first question about trailers, projectionists really have to be careful about just what kind of black leader they are adding to a clip. I recall seeing a DTS Digital Experience trailer played at one theater that had some damage to the tail end of it. To extend some black on the back end, they merely cut some of the lead in on the clip and put that on the back end. The result was a trailer that was virtually unlistenable. Without some of the needed time code up front, it took too long for the DTS unit to kick in. The word "digital" is already doing its flyaround gag by the time you start hearing it in digital. Then when the trailer is finished and going to black --you hear the damned beginning whoosh of the disc fixing to fly into frame. Even if the film frame on that leader is black, that doesn't mean the timecode will always synch up to silence.
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Rick Long
Jedi Master Film Handler
Posts: 759
From: Toronto, Ontario, Canada
Registered: Nov 1999
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posted 06-18-2001 11:39 PM
Here in Ontario, we dont get the ratings bands with the trailers, so I guess black leader is the way to go. An extra cue would not work as there is only one cue that triggers the stop timer sequencer. (Sorry if I wasn't clear about that before). I have done something similar to what Brad suggested by putting the digital default line in series with the micro-switch on the change-over so that it can only default if the change-over is up. (Cinemeccanica console automation and Victoria 5 projector). As Brad mentioned, there is no problem with the three deck units. Thanks for the clarification, Bobby, btw, I have heard that too.
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Dustin Mitchell
Phenomenal Film Handler
Posts: 1865
From: Mondovi, WI, USA
Registered: Mar 2000
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posted 06-19-2001 02:18 AM
The drop out issue IS a problem. At our theatre, the attached trailer is always the last preview, followed by a :20 snipe for the local radio station that's our marketing partner, policy trailer, sound, and then feature. Here is the problem, many times the DTS won't kick out at the end of the attached trailer, and you'll actually here the opening music of the feature for a few brief seconds. Rather embarrasing, having the Fox or Universal logos (very recognizable to the audience) play for a few secnds over the radio snipe. The answer of course is simple, put some black leader between the two. But sometimes someone will forget.
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