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Author Topic: Dolby Digital vs. DTS Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 12-29-2003 04:36 PM                     Are you missing a ton of frames at the reel changes maybe?  |  IP: Logged Antonio Marcheselli Phenomenal Film Handler Posts: 1260 From: Florence, Italy Registered: Mar 2000 posted 12-29-2003 04:38 PM                        What do you mean?  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 12-29-2003 04:59 PM                     Exactly what I said. Are you missing a bunch of frames where you make your splice? Being in Italy, I am guessing you pretty much only get used prints that have many frames lost at the leaders, meaning when that splice comes up, the audio is "jumping" over those missed frames since they do not exist to play it, and what you are hearing is nothing more than a jump in the sound. DTS has a cross-fade implemented on their splices, so that is why I feel it may not be as obvious.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-29-2003 05:07 PM                     Note I said the the latest DA-20's buffer 4 seconds of audio. I'm not totally sure about the older units, CP500's and such. But it does not seem to methat they buffered more than a second or two at most. I may be wrong though and perhaps Steve G. might want to chime on on this. I do know that DTS has always buffered 4 seconds of audio. But DTS also USED TO HAVE lots of time code read and tracking related problems as well making the buffered audio usless. Those problems have obviously been cured though as reading a second or two of DTS time code allows the DTS to keep on outputing audio for 4 seconds no matter what....even if you shut down your projector. The last DA-20's that I installed did exactly the same thing with the 4 seconds of buffered audio.....shut down the machine and the audio keeps playing from the buffer. With SRD if you have a high error rate print or as Brad said, if your penthouse is out of alignment then a splice going through will be obvious. Mark  |  IP: Logged Antonio Marcheselli Phenomenal Film Handler Posts: 1260 From: Florence, Italy Registered: Mar 2000 posted 12-29-2003 05:40 PM                        Brad I live in Italy, not on Mars! We have our labs (Technicolor, Deluxe and Cinecittà plus many little others) that prints hundreds of copies each week. Since I work for a multiplex (Warner Village Cinemas) I always receive brand new copy of print! However I do not mean the jump on sound caused by chopped frames but an instantly hesitation on sound when splice pass. I have to say that in the past with my CP500 and older prints the splices were more audible! Mark Do you mean that on DD prints future data is printed at the end of reel to compensate the splices? Bye A  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 12-29-2003 06:36 PM                     Sorry Antonio, I don't know the distribution specifics outside of the US, just that an awful lot of US prints get sent to the rest of the world, frequently with laser scribed captions. If you have brand new prints and you hear a dropout of any sort, your reader is not set up properly or your splices are something nasty.  |  IP: Logged Antonio Marcheselli Phenomenal Film Handler Posts: 1260 From: Florence, Italy Registered: Mar 2000 posted 12-29-2003 06:49 PM                        No, in Italy we have ALL dubbed prints. Brad/Mark I agree that with CP650 and new readers (my situation) the splices can barely heard. Perhaps I'm the only one in the audience that can hear them (it depends on the prints) but they're there! Bye A  |  IP: Logged Max Biela Film Handler Posts: 89 From: Dortmund, Germany Registered: Sep 2003 posted 12-30-2003 03:58 AM                     No brad, we are sometimes getting prints that are brand new and have a high error rate. "Finding Nemo" had an Error rate of 6-7 in the first week! And no, its not our Reader, the Ice cream Commercial (running for nearly a year now) tracks 3, some new trailers even 2! We are not the only cinema that is having problems with SRD.. We don't get DTS-Disks either - because of piracy Max  |  IP: Logged Alan Haigh Film Handler Posts: 45 From: Watford, UK Registered: Jul 2003 posted 12-30-2003 04:44 AM                    One thing no one has mentioned is the effect of the source material on the listening test. SRD is very cleverly "tuned" to the average soundtrack, with average cinema loudspeakers in the average cinema. It's when it's taken out of this environment, such as, say with classical music in a rich acoustic, or with good hi-fi speakers, or in a small listening room, that differences are more noticeable. Here the "numbers" of the data rate win out. It is miraculous just how good SRD sounds at 320kB/s or whatever it is, the "algorithm" person is a true genius, who has ears and uses them! However, we CAN do better!  |  IP: Logged Kevin Wale Expert Film Handler Posts: 167 From: Guymon, OK USA Registered: Aug 2003 posted 12-30-2003 09:30 AM                     I've never heard a drop in sound at the exact same time I see the splice. It's always after or before. The DTS reader is usually on top of the projector so if DTS was going to drop out, it would likely be before the splice is seen since the splice will pass through the DTS reader berore it passes through the film gate. Dolby is often on top or bottom but either way, there would be a noticable delay between seeing and hearing the splice. Lab splices are that way. I often find them by hearing them 'pop' through the optical. Watch it again and it's seen before heard. I haven't seen very many DD presentations but I wouldn't use a tendancy to drop out as a very harsh judge because DTS has it's own drop out tendancies. If Brad can keep them from dropping out, it would seem to me that drop outs are for the most part either impropperly set up equipment, or the operator/s maybe not cleaning things or whatever. Splices are very seldom in the middle of a high volume of sound so I would think that a properly set up system should survive such dropouts virtually unoticed. Recovery time I guess becomes the major issue here, but again if things are set up right, much of the equipment out there performs well in that department(referring to the dolby processors.) Basically, Dolby requires more attention to be payed when building up a print(Isn't that a good thing?) and probably needs things to be cleaned more often and the film taken better care of. From what I have heard, read, and seen the formats all work like the're supposed to. Otherwise there would be no theatres messing with the ones that don't and I've heard of many theatres running DD that don't seem to have dropout issues. I also agree that there is no comparison unless it is in the same room in most cases. The rooms themselves can greatly affect things. Also, things tend to drift. EQ and whatnot need maintained. Temp changes, pressure changes, humidity changes. You can't expect things to hole the same. Therefore you can't really assume the two rooms would be the same. We had a power spike followed by an immediate blackout. The next day the surrounds in two of hte auditoriums were 10 dbs louder than they were and that much louder than the stage speakers. Also, one side was louder than the other. Had to run in analog that day until we could re eq the room. Other houses had other issues. Some were fine. There are just too many variables that can occur(even overnight) to fairly judge things in two different auditoriums.  |  IP: Logged Darryl Spicer Film God Posts: 3250 From: Lexington, KY, USA Registered: Dec 2000 posted 12-30-2003 10:57 AM                    I think there may be some confusion here about the Dolby Digital and buffering. It is impossable for the Dolby units to buffer 4 seconds because there is not way to advance 4 seconds ahead of the soundtrack to buffer the information. However, Information can be buffered but it is only 4 of the individual blocks that are on the film or one frames worth of information. That is the amount of time allowed for a fault to occure. Anything longer it will drop out. The first DTS units, the ones used for Jurrasic Park only had a two second buffer on the timecode board. That was changed when they updated the firmware chip. We had to send that unit in years ago because of dropout issues. They told us that the firmware had to be updated to extend the buffer. This was before they started sending the chips out for field instalations.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-30-2003 12:57 PM                     Daryl, Perhaps then you could explain why the last two DA-20's I installed continue playing back audio for a couple of seconds after the film has stopped moving??? Also keep in mind while you're trying to figure this out that these are on DP-70's and the delay setting is guite large. Mark @ CLACO  |  IP: Logged Darryl Spicer Film God Posts: 3250 From: Lexington, KY, USA Registered: Dec 2000 posted 12-30-2003 01:17 PM                    note a quote that you made: quote: Dolby is also at least this good in their buffering system but you cannot be missing more than 4 consecutive blocks of data, or one full frame for it to not revert to analog. My thinking is that the Dolby Digital track has a delay based upon where the reader is placed. THis delay is probably about 3 seconds on the DP70. That is raw infoprmation that is sent to ram waiting to be processed. However, if their is an error that faults within the four block area it will switch out of digital. With this there is no buffer since there is no oversampeling to correct the error. Note: I am not saying that the DA20 does not sample the information. It just can not go back and sample it again. With DTS the cdrom reads four second ahead on the disc samples the information and puts it in a buffer to play. As that buffer dumps it keeps repeating the process. That is why timecode can be gone for four seconds without dropping out. When the buffer is empty there is no more information. So in a sense there is a buffer but then there really is not one.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-30-2003 02:32 PM                     Darryl, I agree its a data buffer, data goes into memory and the processor continues to process that data till the memory is cleared. I didn't actually mean that it stores 3 or more seconds of actual audio. That would require ungodly amounts of RAM. With that ability it would seem to me that DD would be able to work the same as DTS if they wanted it to. If it missed 4 blocks or more it would keep outputing audio based on how far it was actually being read ahead....till it could read good data again and then simply drop data blocks to go back in sync again. Only if it ran out of buffered memory then it would revert to analog till more good data came by. I've got to wonder why they didn't go that route...makes too much sense. Perhaps thats one patent that Ray doesn't own and can't buy...... Mark @ CLACO  |  IP: Logged Antonio Marcheselli Phenomenal Film Handler Posts: 1260 From: Florence, Italy Registered: Mar 2000 posted 12-30-2003 05:31 PM                        Mark, I don't knwo much on this but... Since DD reader can be installed on top of the projector the processor should have a sound buffer since the sound is read in advance of the projection. I do not know how much space is allowed for installing a dolby reader but my CP650 setup software go up to 512 perforation that are 128 frames that are 5.3 seconds of sound buffer from the analog "time". I think that it would be strange for Dolby to have "future" datas on that little square of white and black pixels!!! Bye A  |  IP: Logged

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