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Topic: SDDS

Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 07-17-2003 05:33 PM

quote:
My hearing is still very healthy physiologically, thank you. It is about 10 times better than you guys` hearing anyway, since I am a trained musician

Michael, here in America we call that a load of [bs]

. You do NOT have to be musically trained to hear a friggin' DCM. That's just stupid. Now maybe someone doesn't know what note something in the audio tyrack is at, but that doesn't mean that they can't hear it. Again, being able to hear higher frequencies is the key here, not anything musical.

It is also a known scientific fact that the older we all get, the worse our hearing gets by definition. Sure many people have damaged their hearing and suffer hearing loss at an earlier age then they should, but you get someone nearing retirement and they simply cannot hear those higher frequencies that make DCMs obvious. Google it if you think I am kidding.

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David Stambaugh
Film God

Posts: 4021
From: Eugene, Oregon
Registered: Jan 2002

posted 07-17-2003 05:41 PM

If what I noticed in "Episode II" was DCMs, it was *very* obvious. OTOH, if as Michael says, it's normal to have frequent but very brief DCMs, I'm having trouble understanding how they could not be noticeable in a 3-hour flick like "Two Towers" which seemed flawless to me. And I have no trouble picking up on audio anomalies, like when SR-D makes that subtle "splice" sound if the error rate is very high...

FWIW. [Big Grin]

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 07-17-2003 06:09 PM

David, a properly printed SDDS track handled by professionals (yeah I know, a rare thing) being played back on a properly calibrated SDDS system will not drop into DCM mode at all.

Since you generally see movies in their first weekend, even the crappiest theaters frequently haven't had time to do their film damage yet. Now go find a theater that has been running the same print for 3, 4 or 6 months and then you will see what separates the professionals from the ushers. [thumbsup]

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Ken Lackner
Phenomenal Film Handler

Posts: 1907
From: Atlanta, GA, USA
Registered: Sep 2001

posted 07-18-2003 01:55 AM

David said,

quote:
And I have no trouble picking up on audio anomalies, like when SR-D makes that subtle "splice" sound if the error rate is very high...

What do you mean by that? Are you talking about at a splice, or something that sounds like a splice due to some error?

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 07-18-2003 02:10 AM

On SRD if the print is worn or the reader isn't aligned well, the unit can sit at 6 or 7 and then when splices pass it will dropout for a split second...not enough to fallback to SR, not even enough for most people to notice, but it can and when it does the error display never goes to "F". You can see when it happens on the same card as the error display is though, as a red led will blip. The secret is of course to take care of the prints and have a competent tech align your SRD readers so that doesn't happen in the first place.

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Michael Schaffer
"Where is the
Boardwalk Hotel?"

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

posted 07-18-2003 06:16 AM

quote:
David, a properly printed SDDS track handled by professionals (yeah I know, a rare thing) being played back on a properly calibrated SDDS system will not drop into DCM mode at all.

Ahaaaaaaa! [Wink]

quote:
OTOH, if as Michael says, it's normal to have frequent but very brief DCMs, I'm having trouble understanding how they could not be noticeable in a 3-hour flick like "Two Towers" which seemed flawless to me.

I didn`t mean that it is normal or OK to have frequent DCMs, but that often they occur without anybody noticing, because they are mostly very short.
If you have long series of long DCMs, that indicates alignment and/or print problems like Brad said. I have found that long DCMs mostly occur on the left side of the theatre. That side is stored on the P track, and I have had many prints which had very badly printed P tracks. It seems to be/have been a general problem due to the construction of some printing machines, but I forgot the details.
Under real life conditions, there will always be a few DCMs. If you sit through a 3h movie, you can not be fully concentrated all the time. Maybe there were a couple of DCMs. However, if they were not noticeable, that proves that the concept is a good one. If the same system had been set up tp revert directly to analog, you might have heard one or two dropouts. This way it seems to have been an entirely undisturbed movie experience.
Brad - I didn`t say you need musical training to detect DCMs. I just mentioned that it gives you a higher level of aural perception in response to your inquiry about the state of my hearing (which I also had tested physiologically, as I also mentioned).
But I do not agree with what Mark said: if material is encoded with a lower bitrate, it does not automatically mean there is a drastic drop in perceived sound quality. There are many other factors as well, and as I said (for the 3rd time now), most of the bits on the backup channel are actually saved on the dynamic information which is derived by comparison to the activity on the other channels.
I have too often heard people voice opinions about sound quality on the basis that they have heard/read that the format was more compressed. But when subjected to blind listening tests, the same people in many cases could not point out the differences.

quote:
Are you talking about at a splice, or something that sounds like a splice due to some error?

It does not sound like an analog splice - a short crack -, but like a very short low beep. Once somebody has pointed it out to you, you will always hear it. I am sure you will start listening for it every time you see the first changeover cue from now on.

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Mark J. Marshall
Film God

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

posted 07-18-2003 01:24 PM

Actually, I didn't even know it was a lower bit rate until fairly recently. But I've always thought that the backup channels sounded pretty bad. It always sounded like things just went way out of balance or something. Its hard to find words to describe what it sounds like, but it's bad.

The worst part about a DCM is that most of the time it's a precursor to dropping completely. So then, the audience is treated to TWO DROPS. Oh, goodie.

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Ken Lackner
Phenomenal Film Handler

Posts: 1907
From: Atlanta, GA, USA
Registered: Sep 2001

posted 07-18-2003 01:27 PM

I don't know how we migrated to a discussion of SRD, but:

quote:
On SRD if the print is worn or the reader isn't aligned well, the unit can sit at 6 or 7 and then when splices pass it will dropout for a split second...not enough to fallback to SR, not even enough for most people to notice, but it can and when it does the error display never goes to "F".

You said not enough for "most" people to hear. This implies that some people can hear it. If it does not fall back to SR, than what is there to hear?

quote:
It does not sound like an analog splice - a short crack -, but like a very short low beep.

Are you talking about the same thing Brad is talking about? So what causes these momentary disruptions? (Is "dropout" even a correct term here?)

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Michael Schaffer
"Where is the
Boardwalk Hotel?"

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

posted 07-18-2003 02:56 PM

quote:
Are you talking about the same thing Brad is talking about?

Yes.
It is caused by a very short discontinuity of the data and sounds like a low beep or maybe buzz.

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David Stambaugh
Film God

Posts: 4021
From: Eugene, Oregon
Registered: Jan 2002

posted 07-18-2003 03:48 PM

The SR-D "issue" I'm talking about doesn't only occur at splices. It can be every couple of seconds. It's very noticeable when there's music with, say, a long sustained string note or piano note. I've seen a couple of films where that problem was occurring. Can't recall which films right now. Hasn't happened recently though. There was a long thread about it here, and the group's opinion was this "tick" happens when there's a high error rate and "F" is displayed.

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Christopher Seo
Jedi Master Film Handler

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

posted 07-19-2003 02:13 AM

Wait... so, regarding the SRD, are we talking about block repeats or something else?

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Steve Kraus
Film God

Posts: 4094
From: Chicago, IL, USA
Registered: May 2000

posted 07-19-2003 10:45 PM

He's talking about when you momentarily get an F flash even while the overall error rate is a middling or even fairly good number. I used to have some film motion stability issues with one soundhead (basement reader) that had this problem for awhile. Depending on what's going on on the track at that moment you will hear a little tick. That's the best way to describe it and it's most noticable during music with some sort of sustained note or chord.

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Daryl C. W. O'Shea
Film God

Posts: 3977
From: Midland Ontario Canada (where Panavision & IMAX lenses come from)
Registered: Jun 2002

posted 07-19-2003 11:51 PM

To pull the thread even futher away from SDDS...

I've actually had a few CP-500's start making the same ticking noise all by themselves (while running an SRD track). Rebooting the units make the ticking go away.

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Thomas Procyk
Phenomenal Film Handler

Posts: 1842
From: Royal Palm Beach, FL, USA
Registered: Feb 2002

posted 07-20-2003 02:37 AM

We played a VERY used print of Bringing Down The House last week, and I threaded it through the SDDS reader for the hell of it, but left it in Bypass.

The "Data Present" light stayed lit, but none of the levels moved. I noticed this happen with an old trailer, too. The levels would be bouncing along, (sometimes a blip of LE or RE, which would explain what Michael is saying) and then they would all go dead for a few seconds, but there would still be "Data Present" [Confused]

Also on our unit, the "System OK" light stays on only until it starts reading an SDDS track...

=TMP=

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Michael Schaffer
"Where is the
Boardwalk Hotel?"

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

posted 07-20-2003 04:42 AM

What firmware version do you have? You can check the version number on a DFP-D2000 by opening the front door and looking for the firmware on the mini LCD screen.
I haven`t worked with a 2000 in a long while, but it would make sense to me if the level display stayed down since it displays the output levels after the equalizer and there is no output when you leave it in bypass.

quote:
I've actually had a few CP-500's start making the same ticking noise all by themselves (while running an SRD track). Rebooting the units make the ticking go away.

The CP-500 counts the errors and reverts the unit to analog if there are too many errors or the digital track is gone altogether. Rebooting clears that buffer. I have seen that a few times myself. It seems to be a borderline symptom.
That is why you can run a loop and observe the error rate, but it is still very difficult to actually select digital on the front panel. The splice fills the error memory too quickly. But you can trick it by going to the Dolby level screen. When you come back, the buffer has been cleared and you can select digital and see the level displayed for all channels.

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