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Author Topic: Location of soundtrack on film John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 06-28-2006 11:16 AM                     For the DA20 and the DTS-6D, there are rotary switches. So of course you could desolder them and replace them with a remote switch of some sort, or something relay driven. By the way, on the earlier question of what exactly the analog sound offset is, Frank replied, "The diamond for absolute sync of pic and sound at the screen." I think that's not correct. The diamond is actually one frame shorter than absolute sound sync, in order to allow the sound time to travel from behind the screen to the center of the theatre and stay in sync with the picture. So yes, in general, you should thread with picture start in the gate and the diamond on the sound light (be it LED or exciter), but no, that is not the absolute sync point. --jhawk  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 06-28-2006 04:33 PM                        quote: John Hawkinson Frank replied, "The diamond for absolute sync of pic and sound at the screen." I think that's not correct. Well I'll be damned (probably too late), but if every theatre is a different size, how unscientific to put a demarcation for what would basically be correct for only one size theatre seems unscientific. And then why doesn't it say the diamond is for a sync at 50 feet from the screen? Methinks they must have been snorting something very illegal at the SMPTE. So then it must be that SOUND START is not absolute sync either, right? Putting frames that say PICTURE START and SOUND START while wanting it to mean that SOUND START frame isn't really referenced to the PICTURE START frame, except in theatres where the screen is a given distance from the center of the theatre, is IMHO much to spacey for my tastes. John P. where are you? I have to go back and read this spec again; I though I had this down cold but it's getting fuzzier by the minute.  |  IP: Logged Richard Hamilton Phenomenal Film Handler Posts: 1341 From: Evansville, Indiana Registered: Jan 2000 posted 06-28-2006 09:32 PM                     I was doing a late night screening for "pulse"(large format) the night before the premier. The producer leans over to me and says that the sound is 1 frame out of sync! I give him my "bullshit" glance, and then go to the booth and offset the sound 1/24th of a second. What can the average person concieve?  |  IP: Logged Charles Greenlee Jedi Master Film Handler Posts: 801 From: Savannah, Ga, U.S. Registered: Jun 2006 posted 06-29-2006 12:52 AM                        Any marking of sound start on the film, wouldn't be there to indacte synching the sound to the seating. It's probably an indicator of where the optical audio track starts, meaning the offset of picture to that mark would be the same as the offset of the apeture in the film trap to the optical pickup in the soundhead. The synching to the seating would be adjusted on the processor, or a delay module. Digital formats have their delays set in their decoders.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 06-29-2006 09:23 AM                        Standard SMPTE 301 "Theater Projection Leader, Trailer, and Cue Marks" prints the 35mm "Sound Start" diamond in frame 7, and the "Picture Start" in frame 27 -- a 20 frame separation. Standard SMPTE 40 specifies the sound record be printed 21 frames ahead of the corresponding picture frame. So the leader marks pertain to a one frame sound advance, optimum for a person sitting about 50 feet from the screen.  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 06-29-2006 11:59 AM                     John, are 16mm prints normally made without the extra frame of advance, due the the smaller auditoria in which they're normally shown? What about digital projection systems; do they provide a sound sync adjustment for different size auditoria?  |  IP: Logged Jeffry L. Johnson Jedi Master Film Handler Posts: 809 From: Cleveland, Ohio, USA Registered: Apr 2000 posted 06-29-2006 12:22 PM                        quote: John Pytlak Standard SMPTE 40 specifies the sound record be printed 21 frames ahead of the corresponding picture frame. SMPTE 40 also contains an explanatory note that "positioning frame 20 at the scanning point would give synchronism at about 50 ft. from the screen." I don't know the origin of the 20 frame sound sync mark but it was part of the original ASA ZZ22.55.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 06-29-2006 12:34 PM                        quote: Stephen Furley John, are 16mm prints normally made without the extra frame of advance, due the the smaller auditoria in which they're normally shown? Standard SMPTE 41 specifies a 26 frame offset between picture and sound on 16mm prints. Standard SMPTE 301 specifies that the 16mm "Sound Start" is in frame 1 of the syncronizing section, and the "Picture Start" is on frame 27 -- a 26 frame difference. So the leader provides for no sound advance for 16mm, i.e., it assumes the audience is near the screen.  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 06-29-2006 01:01 PM                     Thank you John.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 07-02-2006 04:11 AM                        OK, so today I had to run a film program and also a DVD via an Eiki "Theatre" 3panel LCD projector. So my 35mm film was at the diamond so sound would be synced to a little past the center of the theatre. But wait...all this sync talk got me thinking....so the 35mm is synced optimally for my theatre so what to do about the video? How does the video world intend to deal with that? I assume that in Digital Cinema, where sound and picture are held in a server, they can be easily separated and off-set by as much as needed and fairly easily. But what about all these situations like mine, where video projectors are used to project all manner of video material (this particular movie was on DVD). Video is now essential if you are going to run any "film" festivals. Anyone else run into this puzzlement? I guess we will have no choice but to move everyone to just a few rows in front of the screen.  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 07-02-2006 05:16 AM                     quote: myself, a few posts back What about digital projection systems; do they provide a sound sync adjustment for different size auditoria? Nobody has answered this yet; I think that they must be able to do this, but I don't know for sure. As for normal video, I don't know of any video projectors that allow you to do this, nor VCRs or DVD players. I suppose that normal video, like 16mm, is normally shown in small auditoria, so it isn't too much of a problem.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 07-02-2006 10:46 AM                        AH-HA! So the digital zealots are mum on this one, eh? My-oh-my....and I thought digital was perfect....in fact, it sucks, especially if you try to stick what should be a HOME theatre technology into a movie theatre larger than say 25 feet. Yeah, yeah, I know....it's perfect if you buy a $120.000 projector and server, but that's not what the multitude of venues can afford who are expected to be able to screen videos produced by the hordes of film majors who now shoot their "film" project on video. And I am not talking about some el cheapo comsumer projector, I am talking what I guess would be called semi-pro units like the Eiki that we have which ran the museum a whopping $30,000. They spent all that cash and the big clunky digital thing can't sync up pix and sound for the audience. Imagine that! So much for the allure of digital....for those who have foolishly been allured.  |  IP: Logged Robert Minichino Master Film Handler Posts: 350 From: Haskell, NJ, USA Registered: Dec 2005 posted 07-02-2006 11:30 AM                        Digital sound and picture delays are trivial; in fact one problem with certain home digital projector technologies is that they have too much image latency for dialog sync without delaying the audio. If any digital "cinema" system doesn't have adjustable picture and/or sound delays it's seriously broken.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 07-02-2006 12:17 PM                        Well I'd am all ears. As far as I can see, unless there is yet another very expensive video delay unit that can dial in various amounts of video delay, tell me how I get to retard the video so that it meets the sound at 60 ft from the screen. Remember, I am not talking about Digital Cinema where picture and sound are in a server and can be manipulated. I am talking about a high-end, 3panel LCD projector being fed directly by Digi-Beta, LaserDisc, DVD and U-matic.  |  IP: Logged Robert Minichino Master Film Handler Posts: 350 From: Haskell, NJ, USA Registered: Dec 2005 posted 07-02-2006 01:17 PM                        A dirty little secret of digital projection is that most projectors (especially those with deinterlacers) have 2 or more frames of latency built-in. At 24 FPS that's about 47 feet per frame, and at 30 FPS it's about 38 feet per frame. So if your audio processing has negligible latency, you've already got a bit of offset. Try getting a lip-sync test in your desired formats and have a look where the "natural" sync is in feet from the mains.  |  IP: Logged

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