The DFP-3000 is merely an SDDS player, which also gives me extra inputs on top of what the CP200 offers for things such as a 5.1 DVD, CDS digital sound, mag dubber, or just whatever comes along.

Bear in mind this is not a commercial theater here.

Not so fast with your "designed poorly" crack. With Dolby and SDDS, there has to be processing of the incoming video data to convert it to a contiguious bit stream that then gets processed into audio.

Sure, one way would be to have two identical "front ends" to give each projector it's own video processor and digital decoder and then merely switch the output of the digital processor so the projector plays. This scheme would not need motor relays. However, it would require twice the processing and cost nearly twice as much.

However, the bulk of these installations are going to be for single-projector. Do you expect every purchaser of SDDS or SRD to have to pay a substantial cost increase to have the 2nd projector capability? With the analog optical soundtrack, the increase in cost to support a 2nd projector is very minimal but this is not the case, for the moment at least, for a digtal front end.

So the "cheat" is to share the video and digital processing between the two projectors. Using the motor relays, the video processor "knows" when to start looking at the incoming projector. In this manner, both Dolby and Sony can offer a common unit that can handle either 2 projectors or 1 that doesn't cost significantly more than just making one that handles a single projector.

So the design is not "poor" as you term it but in actuality, "cleaver" and effective. Sony did a better job on theirs in that one can select the changeover delay to suit the installtion and/or operator. Dolby keeps track of when the operator actually selects the incoming projector to get a good match as well. I'd swear that the DA-10 did a better job of this than the DA-20 or CP-500 though.

Now, if you don't want to "cheat," you are certainly welcome to purchase two DA-20s and merely switch their outputs to avoid that nasty motor relay issue.

As to DTS, I'm pretty sure you could switch the TC signals on the fly (either with a relay or with an appropriate MUX) and have decent changeovers. The DTS does a 30msec crossfade when it detects a splice, the same would apply on such a reader switch.

Steve

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"Old projectionists never die, they just changeover!"

I don't object to the idea of needing a relay. I do object to the idea of the customer having to supply it. In my mind, if needed, the relay should be located inside the processor (perhaps on an optional daughtercard or something). This is my personal opinion as to how systems should be designed, and I can understand if you don't agree. Fundamentally it comes down to how "plug and play" a system should be, versus requiring custom hardware, equipment, knowledge, etc.

So to answer you directly: "No," I don't expect 1-projector systems to pay a substantial cost. I think a relay is not a substantial cost .

As for DTS, I thought it was a 300ms crossfade, not a 30ms. But since 300ms is 7 frames, and 1 frame is 42ms, perhaps you are right. Still, when I hear the fade audibly, it sure seems like more than 30ms. Not that I'm the hallmark of human audio perception or anything.

--jhawk

Dolby should supply the relay eh? For who's projector? Does yours have 120V or 230V? Is it single phase or 3-phase? AC or DC (yes some have used DC motors so they can have variable speed). 50Hz or 60Hz? Does your projector use pulse start (like the AA-2 and other european projectors) or continious? Just where do you hook it in?

Now to the installation...so lets say the entire world worked on 120VAC 60Hz single phase motors. After all, we are Americans and are arrogant about such things . So now what? You need to run a 120 volt line from each projector to the sound processor. You have a high-voltage line to deal with all of the way back to the soundrack (2-projector booths don't often use consoles for their sound systems and by definition, one definately doesn't have the processor in the rack). What are the lazy technicians gonna do? Well there is that solar cell line that runs at mic level that goes from essentially the same places so you have this prolonged parallel run with the cell. One or both of those runs are bound to have a changeover command with them as well. If you are lucky the back emf spike from the motor turning on won't cause a false trigger on the changeover line. I guess Dolby and Sony should provide a capacitor for that too huh?

And speaking of changeover command lines, all these years everyone has required the installers to provide their own changeover command, typically by a latching relay (P&B KB series typcially)...the slackers, no wonder they thought they could get away with those motor relays! But you called em on it John!

Ok, the above is a bit over the top but it goes to illustrate that your arguement has little to no merit. This is PROFESSIONAL equipment and the installer is expected, quite reasonably, to provide the unique interfaces specific to the equipment that is being matched up. This is, of course within reason. Dolby provided a reasonable interface that will allow an easy interface with common parts in most installations (I'm sure there is some projector out there that can be shown to make it difficult).

Heck for single projector users (again, the vast majority), Dolby DOES provide a wire link so it is "ready out of the box."

Running two low voltage, low current DC lines to each projector via an interface relay, is the best solution to the problem thus far.

Now if you want to pick on Dolby's design on the whole motor start relay issue go for the easy one....WHY did Dolby decide that both motor relays and the changeover common wire(s) should SHARE a single pin on a 9-pin D-sub? 3-4 wires on a d-sub pin (pin-5 to be specific) is a bit much! To then proceed to not define pins 6, 7 and 8 adds insult to injury! Making this mistake on the DA-10 is one thing, to perpetuate it to the DA-20 and all later processors is inexcusable.

Steve

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"Old projectionists never die, they just changeover!"

However, I have the basement readers. IIRC Dolby Digital is 26 frames ahead of picture. I'm reading it at roughly the analog position or about 20 frames ahead of picture. I do kinda wonder if the relay-induced digital C/O really serves any purpose since in my opinion 7.75 seconds after motor start (minus the offset) is too long and the manual one will only be about 1/6 second too late anyway.

It has been 2033 days since the last post.

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