Film-Tech Forum ARCHIVE: Digital Offsets

my profile | my password | search | faq & rules | forum home

»	Film-Tech Forum ARCHIVE » Operations » Film Handlers' Forum » Digital Offsets (Page 1)

This topic comprises 3 pages: 1 2 3

Author

Topic: Digital Offsets

Mark J. Marshall
Film God

Posts: 3188
From: New Castle, DE, USA
Registered: Aug 2002

posted 11-04-2002 02:35 PM

Does anyone know the offsets of the DTS, SDDS and SR*D digital tracks on 35mm?

Thanks in advance,
Mark

| IP: Logged

Bill Gabel
Film God

Posts: 3873
From: Technicolor / Postworks NY, USA
Registered: Jan 2002

posted 11-04-2002 02:40 PM

On what type projectors? And penthouse or basement readers?

| IP: Logged

Adam Martin
I'm not even gonna point out the irony.

Posts: 3686
From: Dallas, TX
Registered: Nov 2000

posted 11-04-2002 02:48 PM

I think he means on the film itself where the soundtrack is in relation to its corresponding image area, like the analog offset.

| IP: Logged

Stephen Furley
Film God

Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002

posted 11-04-2002 02:55 PM

SR*D is twenty six frames in advance of picture. I think, but I'm not absolutely certain that the others are printed in level sync with the picture, I'm sure Karen can answer for DTS, do we have any SDDS experts here? I recently read some material on CDS which stated that this system was in level sync.

It doesn't matter what type of readers you have for SR*D, the track is still in the same place, it just uses a longer delay the higher up the reader is, I don't know what the maximum is.

Kinoton now make a dual guage (35/16mm) projector where the 16mm (analogue) soundhead is above the gate and the sound is delayed by the necessary amount. Within certain limits it no longer matters where you put the sound head with digital systems. I assume the Kinoton machine digitises the analogue 16mm signal, I can't imagine that they delay it several seconds by analogue means.

| IP: Logged

Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4143
From: Boston, MA
Registered: Apr 2002

posted 11-04-2002 05:03 PM

The SDDS S-side (sound side) track is in editorial sync with the picture while the P-side (picture side) track is 17 frames behind.
I think the Dolby Digital data is 26 perforations ahead of the analogue sound. If I am not mistaken here, that means the data are 21 frames (analogue offset) + 6 frames (26 perforations) = 27 frames ahead. But I am not 100% sure.
Yes, the Kinoton FP38E 16mm soundhead uses a difital delay which can be programmed to various projector speeds and offsets. But it is very difficult to get the sound really in sync with the picture as a tiny variation of the loop size will affect the sync since the frames on 16mm are so small. The other disadvantage is that the machine has the douser and the soundhead coupled. So if you open the douser at the first frame, you will miss the first couple of seconds of audio as the soundtrack is long past the penthouse reader by that time. We have spend a lot of time with the guys from Kinoton at the Berlin Film Festival to solve that problem. In the end, we activated the douser/soundhead when the sound start approached the soundhead and covered the lens with a piece of cardboard until the first frame arrived at the picture gate...
Apart from that, the FP38E is a very good projector with variable speeds and an optional reverse which comes in very handy at the festival as they always want to see the first 1-2 minutes of each film before the screening starts. After the test run, I could reverse the film in the projector. I liked that.

edit - I also think dts timecode is in sync with the picture. But I am not sure either.
But the SDDS information is solid.

| IP: Logged

Christopher Seo
Jedi Master Film Handler

Posts: 530
From: Los Angeles, CA
Registered: Jun 99

posted 11-04-2002 05:44 PM

According to an older SDDS manual, it's actually the S track that lags the P track by 17 frames. Didn't even say where the P track was in regard to the picture. I assume the only reason for this is to reduce the chance of both tracks being damaged at the same point in the audio.

| IP: Logged

Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4143
From: Boston, MA
Registered: Apr 2002

posted 11-04-2002 05:54 PM

You are right there. I was writing from memory. Anyway, the P track is in editorial sync with the picture and the S track is 17 frames behind.
Now we got it right. Yes, the two tracks are offset to each other as each track contains a backup channel for the opposite track.

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 11-04-2002 06:59 PM

The FP-38E 16mm sound issues are long since in the past (years). The exciter lamp turns on with the motor and the sound output tracks with the changeover.

Now they just need to get it right with the 35mm LED issue. They have them tracking with the changeover rather than the motor...silly Germans.

Steve

------------------
"Old projectionists never die, they just changeover!"

| IP: Logged

Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4143
From: Boston, MA
Registered: Apr 2002

posted 11-04-2002 07:03 PM

The FP-38E 16mm sound issues are long since in the past (years). The exciter lamp turns on with the motor and the sound output tracks with the changeover.

But not on the first reel! Or has Kinoton America come up with a solution that the original developers haven`t seen? It wouldn`t surprise me.

| IP: Logged

Karen Hultgren
Master Film Handler

Posts: 492
From: Agoura Hills, CA, USA
Registered: Mar 2000

posted 11-04-2002 07:27 PM

Mark,

The DTS offset is the distance of the DTS reader to the projector's picture gate. The DTS reader must be placed ahead of the picture gate.

To determine the offset value, thread film and count frames from the DTS reader's lens to the picture aperture. Multiply that number by 1.25 and subtract one. If you do not get a whole number, round it off to the closest whole number and put that into the offset setting.

This informmation is in all DTS cinema manuals. The manuals are posted on our free online tech center at here click on 'techcenter' to get access.

Karen at DTS
khultgren@dtsonline.com

| IP: Logged

Tim Reed
Better Projection Pays

Posts: 5246
From: Northampton, PA
Registered: Sep 1999

posted 11-04-2002 07:45 PM

Karen, I think he was wanting to know how much it is offset on the film (during recording) from the actual picture that a particular time code frame syncs with.

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 11-04-2002 08:45 PM

Actually, it was Kinoton America that forced the change that is on all new FP-38E projectors...so yes the first reel is fine too. There is a relay on the backplane of the 16mm sound system...it's job is to disconnect the output of the delay from the "party line". The relay only allows sound to play IF the changeover is open. Since the exciter lamp is turned ON the moment the "FWD" button is pressed, the delay starts filling immediately (with the wind up noise and such as the flywheel comes up to speed). By the time you open the douser on the first reel (or changeover) the buffer is already ready and waiting...when the douser open button is pressed, all is well.

This has been in effect for about 2-years now.

Steve

------------------
"Old projectionists never die, they just changeover!"

| IP: Logged

Michael Schaffer
"Where is the
Boardwalk Hotel?"

Posts: 4143
From: Boston, MA
Registered: Apr 2002

posted 11-05-2002 04:24 AM

That is sad news in a way. We had the problem at the festival in February 01, and again in February of this year. When obviously the American office had already found a solution. Well, it doesn`t really surprise me since there isn`t even much communication between the mother house in Munich and the Berlin office.
When the FP30E came out, there were sound problems because the electronic intermittent transports very quickly and the film hadn`t completely calmed down at the soundhead. We had them install another roller between intermittent and soundhead on our projectors at Sony Center. Munich was still shipping projectors without that roller for a long time after we already had the solution.

| IP: Logged

Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 11-05-2002 07:57 AM

For some reason, I thought they had posted the mod at Kinoton America. Instead, if you go here

You will be instructed to contact them for the modification.

If you obtain the current drawing on the 16mm backplane, (it ends in /01) the modifications should become somewhat apparant. Or you could simply email Kinoton America.

Steve

------------------
"Old projectionists never die, they just changeover!"

| IP: Logged

Mark J. Marshall
Film God

Posts: 3188
From: New Castle, DE, USA
Registered: Aug 2002

posted 11-05-2002 09:22 AM

Holy cow! Wow. I'm sorry I missed my own conversation here! :-)

Anyway, yes, I was looking for the offsets on the FILM itself. So far, it looks like we have:

SR*D: 26 frames ahead of picture.

DTS: In sync --- ?

SDDS: P Track is in sync with picture, S Track is 17 frames behind picture.

CDS: In sync - we think.

Thanks!
Mark

| IP: Logged

All times are Central (GMT -6:00)

This topic comprises 3 pages: 1 2 3

Printer-friendly view of this topic

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.