Film-Tech Forum ARCHIVE: Location of soundtrack on film

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Posted by Ken Lackner (Member # 1002) on 10-13-2003, 12:08 AM:

I just wanted to confirm something. On the optical track, the sound is located 22 frames ahead of the picture, right? What about on the various digital tracks?

Posted by Paul G. Thompson (Member # 655) on 10-13-2003, 12:15 AM:

I thought it was 20 (Inclusive)

Posted by Stephen Furley (Member # 1277) on 10-13-2003, 02:11 AM:

The other formats are:

Standard 8 magnetic 56 frames in advance
Super 8 magnetic 18 frames in advance
9.5mm optical 26 frames in advance
16mm optical 26 frames in advance
16mm magnetic 28 frames in advance
35mm magnetic 28 frames in retard
35mm Dolby Digital 26 frames in advance
35mm CDS in level sync
35mm SDDS is different on each edge, I can't remember the details, but there was a post about it a few months ago.

9.5 mm magnetic seems to vary, there were separate sound bases available some of which had a long path from the gate to the sound head. Also, some machines used a stripe on the left edge, and some on the right!

17.5 mm (the Pathe Rural version, all the other versions were far too early to have had a sound track) is an odd one, there were two standards, 20 and 26 frames in advance, one was used in Europe and the other in America, though the format was never very popular there. I can't remember which was used where.

Can anyone give me the figures for:

70mm Fox Grandeur optical.

The proposed 55.625mm six perf Cinemascope 55 release format.

Super 8 optical.

Standard 8 optical (I have seen a short sample, but I don't think the format was ever adopted).

Any others.

Posted by Dean Kollet (Member # 1789) on 10-13-2003, 06:45 AM:

I was also wondering about this....say that Dolby Digital is 26 frames ahead. Does a penthouse reader have a delay in it so that the sound syncs correctly? Our theater has a Dolby Basement reader, but it's been broken since before I've been there and I've never used it. I'm guessing the basement reader doesn't have delay and the penthouse does?
thanks

Posted by Mike Rendall (Member # 1499) on 10-13-2003, 07:01 AM:

I don't know the offset delay for SR-D, but both penthouse and basement readers have a delay. I think the sound is sufficiently ahead of the picture so the reader can be mounted anywhere on the projector.

Posted by Stephen Furley (Member # 1277) on 10-13-2003, 07:53 AM:

quote:
Does a penthouse reader have a delay in it so that the sound syncs correctly?

Not in the penthouse itself, the delay is handled by the digital processor or adapter.

The basement reader also needs a delay, as the digital reader is less than 26 frames below the gate. The delay can be set, in steps of one perf, up to a specified maximum, the details are in the digital processor/adapter manual.

Posted by John Pytlak (Member # 331) on 10-13-2003, 08:18 AM:

The offset for 35mm analog optical sound is 21 frames, per standard SMPTE 40-2001. In other words, if you see a gunshot on a film, the sound modulation of the "bang" will be 21 frames ahead of the frame that shows the gun going off.

In most theatres, the projector is threaded with about a 20 frame offset between the picture and analog sound pickup, to allow for the approximately 1/24 of a second it takes for sound to go from the screen speakers to the center of the audience. For small screening rooms, drive-in theatres, or telecine, the 21-frame offset would be used.

Standards may be purchased from the SMPTE:

http://www.smpte.org/smpte_store/standards/

Posted by Dominic Case (Member # 1830) on 10-14-2003, 12:04 AM:

SMPTE 40 shows 21 frames offset, but the Academy Leader (the one that counts in feet from 12 to 3) and some others provide marks for a 20 frame offset, which is also widely used.

Posted by Brad Miller (Member # 2) on 10-14-2003, 01:19 AM:

quote:
Standard 8 magnetic 56 frames in advance

Ummmmmm, I don't think so. [Wink]

It's been way too long, but I think it's 18 frames in advance.

(Yeah, I know...probably a typo.)

Posted by Phil Hill (Member # 371) on 10-14-2003, 02:53 AM:

Super8 is 18 frames in advance of the picture. I do think that Reg8 is 56 frames.

35MM Mag is 28 frame lag

70MM Mag is 23 frame lag.

If I remember right, I think SMPTE specs all with +/- 1/2 frame from the center of the pic to the associated audio.

Also, it is common as John mentions, to "short" thread an extra frame between the pic and sound for deep theaters to compensate for the sound delay.

>>> Phil

Posted by Jeffry L. Johnson (Member # 453) on 10-14-2003, 07:38 AM:

"The Focal Encyclopedia of Film & Television Techniques", ©1969, SBN 8038-2268-5:
Film Dimensions and Physical Characteristics:
Sound Advance:
8mm Magnetic sound: 56 frames ahead of picture +/- 1 frame (Regular 8 or 8-mm Type R)
Super-8 Optical sound: 22 frames ahead of picture +/- 1/2 frame

I did a quick scan and do not see current SMPTE standards for these formats.

Posted by Stephen Furley (Member # 1277) on 10-14-2003, 07:58 AM:

Phil, thank you for the info on 70mm. 23*5/4=28.75 so just slightly longer than the path for 35mm.

Brad, not a typo, I'm pretty sure the 56 frame figure is correct, but if not, then it's a brain malfunction, not a fingers one.

I used the term 'Standard 8' which is almost universally used here, but I don't think it was ever officially used by Kodak. Phil used the term 'Regular 8', which is less common here. I don't know if this term was ever used by Kodak, they tended to just call it '8mm', which became rather confusing after the introduction of Super 8 in 1965.

To return to the sound advance question, it is much greater on Standard 8, than on Super 8. I think the 56 frame figure is correct, but I'll come back to that in a minute. This distance would, in some ways, make sense. Firstly, it would be the same distance as the 28 frame magnetic advance on 16mm, which would simplify the design of 16mm/Standard 8 dual gauge projectors. I don't know if any sound ones were actually built, but there were several silent ones, so it's possible. Secondly, the greater distance made it easier to design a separate sound base to be used with an existing silent projector. These certainly did exist, though they were more common for 9.5mm. Most silent projectors did not run at a constant speed, you adjusted the knob until it sounded right, and kept adjusting it as the machine warmed up!

Later, dual format Standard 8 / Super 8 sound projectors were introduced, and on these the difference in sound advance was a problem. I have one from the late '60s, which threads automatically through the gate, but manually from that point on. There are dotted lines cast into the metal casing of the projecter, showing the correct size lower loops for the two formats, and the Standard 8 one is very large. On later machines, which had fully automatic threading there was a horribly complex plastic guide system which formed the correct sized loop, depending on which gate was installed.

I few companies built 8mm projectors with reasonable sound systems in them, e.g. Elmo, but most were terrible, there was no proper sound drum, and certainly nothing like a 35/70 magnetic reader, just a system which would have been more at home in a tape recorder. Standard 8 sound was not common, I have a few shorts in my collection, it was purely a home movie system, and the equipment was very expensive for home use, few people bought it. The stripe was outside the perforations, exactly like the balance stripe on 16mm, and the combination of the rather large perforations alongside the track, the primative sound head design and the large loop of film flapping about made the system rather unstable. Super 8 was designed from the start to have magnetic sound, and in later years there were machines which could play a second track from the balance stripe. It is still possible to buy Super 8 prints with 4 channel (matrixed) tracks, and the sound is pretty good, I don't have any, the cost is not a great deal less than for a 35mm print! I think about 600 to 800 pounds for a full length feature.

Super 8 did have some non-home use as an exhibition format, the airlines used it, with optical sound, for a while before switching to video. It was also used to a limited extent in education, and was under serious consideration for television news work, but the idea was dropped when portable video equipment became available.

I have a couple of 8mm sound machines in my store, unused for several years. I have to go there in the next few days to get out a pair of Bell and Howell 666s which somebody is borrowing for a show, I'll check the sound advance on Standard 8 while I'm there.

Anyway, enough of this bootlace stuff, I'm heading up to york next month to hear (and see) the 70mm; anyone else going to be there?

Posted by Paul G. Thompson (Member # 655) on 10-14-2003, 11:46 AM:

John P is right. It is 21 frames (inclusive.)

I always seem to get "inclusive" and "non inclusive" screwed up.

Posted by Ken McFall (Member # 845) on 10-14-2003, 12:18 PM:

Paul I have just refreshed my memory from the orange BKSTS manual that clearly states 20 frames!

Using a standard leader you laced a number in the gate, say 9, and the star that was printed before 10 lined up in the sound head. As the star was four frames before the number it was 20 frames.

Now I'm not too sure if this makes sense but if you consider the middle of the frame with the number and the corresponding star which is in the middle of the frame that would make it 19 frames!!!!!

I was always confused by this whole thing as trying to lace an FP20 with 20 (19) frames sync made for very small loops.

Posted by Frank Angel (Member # 248) on 10-14-2003, 12:19 PM:

There was a very sophistocated system years ago, circa 1960s from a company called Inner Space, that married a tape deck to the camera and projector. You sent them your S8mm camera and they modified it so that it could output a pulse for every frame advance. You used a portable tape deck, typically a Uher or Nagra which recorded the pulses on one channel and audio on the other. For playback, a reader on the projector shaft was fed to a controller which varied the speed of the tape deck by generating a drive voltage based on the projector shaft speed compared to the pulse count from the control track on the tape deck. It worked quite well, the only drawback being it your projector had really unstable speed problems, you could hear the speed varying in the sound. But any decent projector that kept reasonable steady speed worked fine.

You didn't even have to worry about starting the projector and the deck together because the system also included a circuit that saw a cue on the film and started the tape deck at the same time.

The big advantage over sound on film is obvious. You had the excellent fidelity of very good r-t-r tape transport without any of the limitations of the slow speed of the film and its miniscule mag stripe.

I also recall a system from Revere which supplied you with a tape that had lines printed on the base side and a small mirror that you positioned over the aperture to deflect the intermittent light from the projector onto the tape traveling through the tape deck. The strobe effect would make the lines look like they were standing still when the projector was at 18fps. You would have to continually control the projector speed manually, but it did work if you didn't need lipsync.

Then there were the add-on devices, one in particular that I recall that you put in place of the supply reel. It basically was a record/playback head that film which was mag striped ran through. From what I remember a salesman saying at the time, the sound was attrocious, and of course, it could only be used for adding music or sound effects -- no location sound.

Frank

Posted by Manny Knowles (Member # 1171) on 10-14-2003, 12:35 PM:

Off-Topic -- but I used a pulse-sync system with Super-8 to make a 3D travelogue back in the late 80s.

Posted by Sean Weitzel (Member # 244) on 10-14-2003, 12:36 PM:

One of the most common cameras for Regular 8 sound was a Fairchild Cinephonic Eight. Here are some photos of the camera.

Posted by John Pytlak (Member # 331) on 10-14-2003, 03:53 PM:

Again, the actual offset on the print should be 21 frames. The BKSTS figure of 20 frames when lacing the projector is putting the sound in sync at about 50 feet from the screen speakers, suitable for most theatres.

Posted by System Notices (Member # 2357) on 06-23-2006, 10:40 AM:

It has been 982 days since the last post.

Posted by Iben Jimenez (Member # 3713) on 06-23-2006, 10:40 AM:

But, What does inclusive means in terms of the offset?
The "Picture Start" frame must be in the gate, so I have to count 20 frames including the frame already in the gate?
Where does the light of the mono reader must be, exactly in the diamond, or the division mark of that frame?

Posted by Frank Angel (Member # 248) on 06-23-2006, 11:42 AM:

The diamond for absolute sync of pic and sound at the screen. And the diamond is there for all the number frames (in the Academy Sync Leader) so that you can thread up on, say, number 10 -- i.e., you can use any numbered frame and there will be a corresponding diamond for that frame which you can line up in sound scanning beam.

It sure would be nice if someone designed a projector with an adjustable loop -- a knob that you could just dial the distance marked in feet from your screen to the middle of the theatre. You need 60ft....you just turn the Loop Adjustment knob to 60ft. How sweet it would be...and fairly simple to design.

Posted by Charles Greenlee (Member # 3856) on 06-24-2006, 11:45 AM:

"35mm magnetic 28 frames in retard
35mm Dolby Digital 26 frames in advance"

So DD can be placed in a basment configuration? I've never seen it like that. What all can be done that way? SDDS, DTS, mag?

Posted by Randy Stankey (Member # 64) on 06-24-2006, 11:55 AM:

Advance/retard for Dolby Digital is flexible, depending on the projector, isn't it?

If you have a penthouse it would be retarded. If you have a basement reader it would be advanced.

Further, if your penthouse is set up differently the offset might change, based on how you thread.

The Dolby Digital decoder, the DTS player and the SDDS player all have adjustable offsets just for the purpose.

Posted by Lyle Romer (Member # 1266) on 06-24-2006, 11:58 AM:

I'm pretty positive that DD is the only digital system that can have a basement reader.

Posted by Charles Greenlee (Member # 3856) on 06-24-2006, 12:23 PM:

Yeah our big screen had BOTH DTS and DD, in penthouse no doubt. DTS was top most, then just below it the DD, which put us setting the DTS at a huge delay. The manul said not to set it for over, I forget, something like 30? We had to set it to almost 60 I think. Would have made more sense to put the DD in the basment.

Posted by Richard Fowler (Member # 893) on 06-24-2006, 01:47 PM:

Sondor, which supplies projection/sound equipment for studio and screening rooms have the "Soundhouse" soundhead which can read Dolby Digital + Analog and DTS [Cool]

Built to be used as a penthouse with custom delay for the analog track. MegaSystems was working on something similar but it never came to market.

Posted by Richard Hamilton (Member # 321) on 06-24-2006, 03:57 PM:

Richard,
We have a couple of the analog only penthouse readers out there. It is a B.A.C.P./USL DSTR modified for analog. We sold a few of the 8/70 - 35mm combo projectors. When the idea to add 35mm to the existing 8/70 machine, we realized there was no where to add a basement 35mm reader. The big issue was finding a piece of gear that would delay the signal for about 2 seconds.

Rick

Posted by Phil Hill (Member # 371) on 06-24-2006, 04:07 PM:

I agree Rick, I did the same thing at Iwerks for a 35mm version of the linear loop projector. Dare I mention Peavey <cough> Media Matrix <cough> for the delay? Yikes!

But I do like the Sondor Soundhouse product that Richard mentioned. I would like an "all-in-one" penthouse red system so I can keep my "light bulb" soundhead for old films.

Posted by Ron Curran (Member # 3631) on 06-24-2006, 07:54 PM:

We have our Dolby Digital penthouse mounted on top of the DTS reader. It works. This way we can show trailers in Dolby Digital and a feature in DTS.

Posted by Randy Stankey (Member # 64) on 06-25-2006, 12:28 AM:

In a couple theaters where I worked, there was an issue with stacking digital penthouse readers when the threading path was changed.

It was an SDDS on top of a DTS.

At first, they were set up so that you had to always thread the DTS, even if the movie was in SDDS. Then people started bypassing the DTS if it wasn't being used. That threw the sound sync WAY out of whack!

I had to go back and reset the SDDS so that the DTS was bypassed when it was being used.

(Dumb management decision. I wanted it the other way but I was overruled.)

Posted by Frank Angel (Member # 248) on 06-25-2006, 06:51 AM:

Richard, are those Sondor heads still available (I'd need two)? Phil's still worried about that pesky red vs. white distortion issue as I am -- as should anyone who runs older prints and as should have the SMPTE when cyan was being developed and they KNEW that older white optimized tracks would not play well on them. This gizmo would be the perfect way to switch from white exciters to red exciters and back again, depenting on the print optimization requirement. I mean, we all want to be excited correctly, no?

The Sondor would be the perfect solution al la Mr. Hill. But I also have to ask, how robust is the delay circuit that's employed -- there's digital delay and then there's digital delay. Depending on the sampling rate and such, long delays can sound pretty disgusting. Is this thing well designed? What about the mechanics; good lateral guide roller tolerances, easy adjustment for same, decent damping and flywheel stablization etc.?

PRICE?

To bad they didn't include mag heads as well. That would be just too sweet to have a single piece of hardware sitting atop the projector head.

[ 06-26-2006, 11:09 PM: Message edited by: Frank Angel ]

Posted by Chris Trainor (Member # 9) on 06-26-2006, 08:44 PM:

Randy,

I've got my DTS reader on top of the SDDS... not sure why.. think it was for 'looks'. [Smile]

One thing that's a pain tho is having the SDDS after the DTS makes for a really long delay setting on the DTS processor. I think i'm over their max because of it. Of course, if I don't thread the SDDS reader things go right to hell. [Smile]

The upside is my rigging has SDDS as primary, fallback to DTS and finally to analog.

I keep thinking of swapping the location of the readers just to bring the DTS delay in a bit, but I havn't had any problems so I'm not entirely sure of the benifit. The one thing I can think of is not having to thread the SDDS reader all the time.

--Chris

Posted by Randy Stankey (Member # 64) on 06-26-2006, 09:15 PM:

I see so few SDDS prints these days (I'm in an art theater not commercial/first-run.) that I don't see why you need to thread the SDDS if there is DTS.

I'd reset the delay on the DTS so that the SDDS is bypassed.

But, then again, if I had my druthers the SDDS would be taken off all together. [Roll Eyes]

Posted by Mike Blakesley (Member # 26) on 06-26-2006, 09:18 PM:

quote: Randy Stankey
I don't see why you need to thread the SDDS if there is DTS.

Maybe he:

1. Sometimes doesn't get the disks with the film, or

2. Has a projectionist who forgets to load/swap the disks into the player.

Posted by Charles Greenlee (Member # 3856) on 06-26-2006, 10:01 PM:

The Combo reader sound interesting. How well does it work? "(Dumb management decision. I wanted it the other way but I was overruled.)" Yeah that happens alot unfortunatly. Best thing we can do, is instruct managment on how it works, and how to make it work best, and hope the learn. If not, then we just have to deal with their desicions best we can, till we buy our own houses and show them up. [Big Grin]

Posted by Chris Trainor (Member # 9) on 06-26-2006, 11:24 PM:

Randy:

This is in my home screening room... and every print I've seen that's recent has an SDDS track (tho very few these days have 8 channel soundtracks). I have very few DTS discs for the prints I get. Plus, for some dumb reason I prefer SDDS. When I owned a 2nd run theater only about 20% of the time did I get DTS discs with my prints. Since I couldn't afford Dolby it was easier to just have a 'guaranteed' soundtrack provided the print I got wasn't completely beat up.

--Chris

Posted by Ron Curran (Member # 3631) on 06-27-2006, 01:07 AM:

Which is why, as I said in an earlier post, that our DTS reader is under the Dolby penthouse. Its easier to bypass the DD and ALWAYS lace up through the DTS, which is a snack.

The other way round would mean that the DD reader always had to be laced up.

There are a lot fewer frames of delay to set this way, no matter how you run (O&OEE).

We are mostly second run, so its a toss-up whether we get discs or an unplayable DD track.

Good breaking news: Discs supplied most times (sometimes 2 sets in the box) and more DD tracks readable (I think Kodak found what the problem was). I have no experience of SDDS.

Posted by Gilbert Travin (Member # 2138) on 06-27-2006, 02:03 AM:

Hi all !
For standard 8 magnetic : 56 frames in advance.
I well know the problem : in 1968 I had purchased an Heurtier P6-24 Super 8 magnetic sound projector. This machine was based on the standard 8 model and soundtracks of "commercial" movies were not read correctly. Heurtier free re-synchronized magnetic sound at 56 frames !

Posted by Monte L Fullmer (Member # 2797) on 06-27-2006, 03:13 AM:

quote: Randy Stankey
I don't see why you need to thread the SDDS if there is DTS.

I worked in a 21 complex where we had all three digital units - the top one was the SDDS, and below the Sony, was the DTS reader (SR-d was the basement reader..for CHR P35GPS units..) and the way this was set up was that we had to lace AROUND the rollers of the Sony unit to lace through the DTS reader (if we didn't want to use SDDS..was an option).

Other houses had the CAT-701 mounted on top of the DTS reader and I had to set the CAT-701 delay to where the path went through both units for SR-D to be in proper sync-not around the outer rollers of the CAT-701 if using DTS only. This was instructed my my superior at home office simply .. to keep it simple, stupid...

Posted by Jack Ondracek (Member # 1466) on 06-27-2006, 05:30 AM:

quote: Mike Blakesley
Maybe he:

1. Sometimes doesn't get the disks with the film, or

2. Has a projectionist who forgets to load/swap the disks into the player.

So far this year, we've received 2 first-run prints sans DTS disk. In both cases, ETS has said that "additional print runs" were provided too late to get the accompanying disks.

Beats me if this is true or not... but it doesn't do the DTS image any good.

In both cases, I've been able to get disk images from another local theatre that runs all their prints in SRD.

Posted by Stephen Furley (Member # 1277) on 06-27-2006, 06:47 AM:

Something that does strike me is how few film print formats were originally designed to accommodate an optical sound track. The only ones I can think of at the moment are:

42mm Tri-Ergon.

70mm Fox grandeur.

35mm Vistavision, though that just adopted the track position of normal 4-perf 35mm, which was not originally on that format.

There were one or two other wide film (56mm ish) formats which were contemporary with Grandeur, but I can't remember the details. Also, a few totally experimental formats in the late teens / early '20s.

There are also a few formats which were originally designed for magnetic stripe tracks:

Super-8.

70mm Todd-AO.

Both of these later gained optical tracks, but these were little used, and short-lived.

55.625mm Cinemascope 55. This one never made it into commercial use.

35mm Cinemascope. This was only a slight reworking of normal 35mm, which started out as silent.

Then there was the magnetic Vistavision format for 'Story of a Patriot.

Those are about the only ones I can think of, and most of those never made it into general use. Just about everything else started out as a mute format, and, in some cases, was later modified for sound.

Cinerama, Cinemiracle, Kinopanorama and Imax were all designed to use separate separate tracks.

Posted by Charles Greenlee (Member # 3856) on 06-27-2006, 11:15 PM:

Ok, well here's a question. Which sound format do you prefer? DD, DTS, SDDS, or even analog (Why? Dunno.)? In my experience between dD and DTS, both are pretty comprable, but I still prefer DTS. That is when deluxe doesn't mess up when printing the timecode. I'd say that I'd like to have SDDS, simply because of the 8 channel capability. But I'm told that SDDS doesn't sound quite right. Either something with the way it's compressed, or how it's equalized, either way I'm told the sounds seems colored. Also, SDDS doesn't seem to be active anymore. Prints still come out for it, but Sony's no longer updating it.

Posted by David Stambaugh (Member # 1102) on 06-27-2006, 11:29 PM:

There's only one theater that here that has all 3 digital formats, seen many movies there. SDDS always sounds the best to me. Could just be a fluke with the way it's EQ'd. House #3 at Regal Cinema World 8, which unfortunately will be closed by the end of 2006.

Posted by Ron Curran (Member # 3631) on 06-28-2006, 02:15 AM:

DD seems to be the norm at any other cinema I attend. I haven’t heard DTS or SDDS outside for a few years now, so it is difficult to judge.

At my own cinema, all our systems are kept up to scratch by Intec Pacific and I think DTS is a whisker better. My opinion is coloured by the reliability of the system because I can relax while screening the first run through when I know there are discs. We occasionally run an A-B comparison and none of us could pick a clear winner, maybe DTS by a whisker.

However, I am amazed at how good DD can sound, so if the drop-out rate is fixed (Fingers crossed, it has improved lately) it will get thumbs up, after uncrossing my fingers.

Dolby A and SR can also sound pleasant. It depends a lot on the recording engineers. But I miss the 3-channel surround.

If I had to choose between a mediocre image with digital sound and an excellent image with analogue stereo, I would vote for the latter. If digital didn’t exist, the old wiggly would probably be developed further.

The cyan tracks play a few db down with the red light reader. Yes, we’ve had it checked.

When Dolby stereo was introduced, I remember people in the industry telling me that it was superior to magnetic. It reminds me of the current debate about digital vs film.

Posted by Carl Martin (Member # 1146) on 06-28-2006, 02:55 AM:

is it possible to set up any of the digital formats with different delay options that can be selected? so if you bypass one reader you can hit a toggle switch and the reader above it will still be in sync. or if you have a cobbled-together changeover setup with one basement srd reader and one penthouse reader.

it doesn't seem like you could do this with just one da20. but it should be possible in principle.

Posted by John Hawkinson (Member # 1135) on 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

Posted by Frank Angel (Member # 248) on 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.

Posted by Richard Hamilton (Member # 321) on 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?

Posted by Charles Greenlee (Member # 3856) on 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.

Posted by John Pytlak (Member # 331) on 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.

Posted by Stephen Furley (Member # 1277) on 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?

Posted by Jeffry L. Johnson (Member # 453) on 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.

Posted by John Pytlak (Member # 331) on 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.

Posted by Stephen Furley (Member # 1277) on 06-29-2006, 01:01 PM:

Thank you John.

Posted by Frank Angel (Member # 248) on 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. [Eek!]

Posted by Stephen Furley (Member # 1277) on 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.

Posted by Frank Angel (Member # 248) on 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. [evil]

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. [Razz]

Posted by Robert Minichino (Member # 3495) on 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.

Posted by Frank Angel (Member # 248) on 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.

Posted by Robert Minichino (Member # 3495) on 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.

Posted by Carl Martin (Member # 1146) on 07-03-2006, 01:59 AM:

a week or 2 ago i saw "the puffy chair" digitally projected (by what means i don't know). dialog was quite noticeably following the picture. this was not a big auditorium and i was maybe 20-25' from the screen. offset in the wrong direction perhaps?