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Author Topic: SDDS Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 07-15-2003 03:26 PM                        The two tracks are offset by 17 frames. The picture side (P track) contains C - LC - L - LSr plus 2 backup tracks, the SW channel from the other side and a mono sum of RC - R - RSr. The soundtrack side (S track) contains RC - R - RSr - SW plus 2 backup tracks, the C channel and the mono sum of LC - L - LSr.  |  IP: Logged John Walsh Film God Posts: 2490 From: Connecticut, USA, Earth, Milky Way Registered: Oct 1999 posted 07-15-2003 05:56 PM                     Joe wrote: I often wonder if the space used for the SDDS backup track would have been better utilized as extra error-correction data, reducing the chance of dropouts in the first place.---- It would have been better utilized by adding an SR-D track....  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 07-16-2003 12:33 AM                        quote: It would have been better utilized by adding an SR-D track. Actually, most prints already have an SR*D track. The data blocks are usually found between the perforations on the side of the film next to the analog optical soundtrack.  |  IP: Logged Larry Zuverink Film Handler Posts: 98 From: Caledonia, MI, USA Registered: Nov 2002 posted 07-16-2003 09:58 AM                     Trust me, If the problems are repairable by us we take care of them. One of the main problems we have is the APR-6 board going bad. This is $1500 to send in and have repaired. We just don't see it being worth the cost for a fading format that again is in houses that have two other digital formats.  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 07-16-2003 10:12 AM                    The way the backup tracks are configured makes a drop to SDDS' backup sound really strange. Imagine one side of the room booming along, and the other half all of a sudden sound like a low bit rate mono mp3 file. And then about a second later, if the film is still bad, it drops again this time to the next format, so the effect goes away. It would be nice to configure it to drop completely if it loses either side.  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 07-16-2003 10:28 AM                        The backup channels contain a mono sum of the other side, but you do not hear a significant drop in sound level. If either of the sides switches to DCM (Digital Concealment Mode, as it is called), the output level is matched to the average level of the other channels. Only trained ears can hear a DCM. But: if a DFP is configured for 8 channels, and the movie only carries 6, the DCM will also feed sound to the LE or RE (whichever side is affected) channel which is idle otherwise. Since there is no sound on the respective channel in normal playback mode, the DCM side will actually sound a little bit louder. If DCMs occur frequently, there will be a very slight pumping effect noticeable on the affected side. You can tell a track is going through a series of DCMs if you have a 6-channel movie but the level display flashes on the LE or RE channel from time to time. Instead of configuring it to drop out completely, the way to go is to switch the unit into 6-channel mode. Then the DCMs become almost unnoticeable.  |  IP: Logged David Stambaugh Film God Posts: 4021 From: Eugene, Oregon Registered: Jan 2002 posted 07-16-2003 12:05 PM                        The last film I saw in SDDS that I can recall having a dropout problem was "Star Wars Ep II" at the end of reel 1. It dropped out several times. I think there was a thread here about possible lab printing problems with it. Anyway, the dropouts were *very* noticeable. Several customers reported it to the manager, which in itself is very rare. I don't know if it was dropping to DCM or analog though...  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 07-16-2003 02:50 PM                     quote: Instead of configuring it to drop out completely, the way to go is to switch the unit into 6-channel mode. Then the DCMs become almost unnoticeable. To clarify, then the volume differences become almost unnoticeable...but the lower quality DCM signal is ALWAYS heard. Now people with hearing loss probably can't hear it since it mostly affects the highest frequencies, but it's there and it's annoying. I would take plain old SR any day over an SDDS track that is DCMing, even infrequently. That's why a couple of years ago on this forum I was desperately trying to figure out a modification to the SDDS system so that if it went into DCM it would just fallback to SR.  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 07-16-2003 04:50 PM                        You can hear it better of course in scenes with a lot of acoustic action. In quieter scenes with dialog and fewer effects it becomes almost unnoticeable. It is less noticeable to the average ear than analog fallback (even with well aligned optics and the level set). The DCM track is very compressed, but not bandpassed to my knowledge (or is it? I have to look that up).  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 07-16-2003 09:29 PM                    I disagree that DCM is hard to hear. Just like a left and right speaker playing a mono signal create a "phantom center" channel, a mono signal coming from the front right and back right collapses to create a "phantom right" channel somewhere on the right wall of the theater. It sounds like a black hole just opened up and sucked all the sound from the right speakers. Of course, the low bit rate doesn't help much. But I do agree that the less sound there is, the harder it is to hear.  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 07-17-2003 05:15 AM                        Maybe you should consider installing more than one surround speaker, then you will not have this effect. There should be a group of surround speakers creating a diffuse "surrounding" sound rather than a pinpoint source in the corner. The lower bitrate does not affect the audio quality as much as you might think. One reason it has a lower bitrate is that the backup channel has less dynamics as the actual output level of the channel is adjusted to the average level on the other channels. That does not mean that it does not have a wide dynamic range, only that the dynamics control is applied to the channel rather than stored in the audio data. That is where most of the bits are saved.  |  IP: Logged Mark J. Marshall Film God Posts: 3188 From: New Castle, DE, USA Registered: Aug 2002 posted 07-17-2003 09:59 AM                    With all due respect, you're saying that the low bit rate shouldn't affect the sound quality much, and the more surrounds I have, and the less sound there is on the movie soundtrack the harder it is to hear SDDS drop out. I'm saying that in a THX theater, with 20+ surround speakers, I can hear the right side of the theater collapse plain as day, even if the movie is Alex & Emma. Maybe I'm the exception to the rule.  |  IP: Logged Ken Lackner Phenomenal Film Handler Posts: 1907 From: Atlanta, GA, USA Registered: Sep 2001 posted 07-17-2003 11:20 AM                     Brad said: quote: I would take plain old SR any day over an SDDS track that is DCMing, even infrequently. That's why a couple of years ago on this forum I was desperately trying to figure out a modification to the SDDS system so that if it went into DCM it would just fallback to SR. So did you ever figure it out?  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 07-17-2003 02:17 PM                     Ken, no I never found out, but I was told that such a modification was done for the labs so they could verify the quality of their printing. With as quiet as the SDDS camp is and the restructuring of their cinema division, I'm afraid the format won't be around for much longer anyway. Michael, when is the last time you had a hearing test? (I put the smiley there to show you I am not trying to be mean, but seriously have you suffered any hearing loss?)  |  IP: Logged Michael Schaffer "Where is the Boardwalk Hotel?" Posts: 4143 From: Boston, MA Registered: Apr 2002 posted 07-17-2003 05:02 PM                        I think about 3 months or so ago. My hearing is still very healthy physiologically, thank you. It is several times better than you guys` hearing anyway, since I am a trained musician (I should put a smiley here, as I do not mean this insultingly at all, on the other hand, it is simply true. Well, OK ). I hear the DCMs very well and they bother me too, but what I mean is that the DCM is far less noticeable than complete fallback to analog and most people in the audience generally do not hear it. Many do hear analog fallback however. Mark, I believe you that you hear the effect of the DCM switching on and off, but I do not think you hear the difference in sound quality. You may have read that the backup channel is more compressed, but that does not automatically mean it has a noticeably worse quality. Like I said, in this case most of the bits are saved by applying external dynamic steering. Most of the DCMs you don`t hear anyway, because they are very short. You can verify this by running a print and watching the linear error test on the notebook. You will see that there are many very short DCMs you never knew were there. The ones you hear are only the longer ones. Again, the pumping effect you noticed is mostly caused by the LE or RE channel being switched on and off during a 6-channel movie. Configure the unit for 6-channel playback, and the effect will be far less noticeable.  |  IP: Logged

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