Hardware solution for synched playback of two DVDs on two monitors?

November 27, 2007 11:32 AM

I need to play two separate DVDs at the same time on two separate monitors. The output must be synched precisely as the two signals will work as a single "show" on two adjacent monitors. I need a reliable and idiot-proof way to do this.

This is going to be used at a trade show, so this must be durable. Also, since I will not be there to personally supervise, it needs to be as simple as possible to operate. Non-technical people will run the thing. The show is about 7 minutes, and I would like it to run on a continuous loop.

Is there some kind of dual-DVD deck that will do this? I prefer not to run this from a PC.

Thanks!

posted by Mister_A to technology (19 comments total)

Are you talking about computer monitors with DVI inputs? If so, you could just get any DVD player that has HDMI output, run an HDMI->DVI cable out of it, and use a DVI splitter to split it to the two monitors.

Are you on some kind of budget? DVI splitters are kind of expensive.
posted by ckolderup at 11:54 AM on November 27, 2007

ckolderup: The OP wants to show two different DVDs at the same time, but synced up.

Have you considered just buying two identical cheap DVD players and using one remote to control both of them? They will have the same IR codes, so if they are close together they will both respond to one button press on the remote. As long as you can just press "Play" to start both DVDs, it should be pretty easy to keep them in sync.
posted by burnmp3s at 12:02 PM on November 27, 2007

I have TWO DVDs that function as ONE integrated show on TWO monitors, but ONLY if they are precisely in sync. I don't want to show the same thing on two monitors, I want to show two different things, precisely synced, on two different monitors.
posted by Mister_A at 12:06 PM on November 27, 2007

If you're looking for as simple as possible, burnmp3s probably has the best idea. I used to work at a video store that used a similar setup for duplication, and it was about as close to idiot-proof as you can get.

As for making it loop: you can do that when you burn the DVDs.
posted by box at 12:08 PM on November 27, 2007

Yea, that's a possibility, burnmp3s, but I can imagine something going wrong there pretty easily. If the video is off by even a couple of frames, it's going to be a problem.
posted by Mister_A at 12:08 PM on November 27, 2007

One other thing: what kind of standard of precision do you need? If a couple thousandths of a second one way or the other don't matter, then you won't have to worry about, say, the differing disc-spin-up times between your two identical drives.

If, however, you're looking for NASA-levels of precision, then the question suddenly becomes a lot more complicated.
posted by box at 12:10 PM on November 27, 2007

DVDs are 30 fps, right? So if the sync is off by, say, 1/10 of a second, that's a couple frames right there.

Another follow-up question: how much money do you have available to throw at this problem?
posted by box at 12:13 PM on November 27, 2007

I worked on a similar project back in the day.

What you need:
Two (2) Pioneer DVD-V7400 Industrial DVD Video Players
One (1) BCD VC-16b RS-232C DVD controller

Your rental house/VAR will be able to provide you with the proper cables to connect the players to the controller.

Very important: make sure the discs are authored with no First Play PGC commands and no buttons locked out. Of course, the two programs need to be exactly the same length.
posted by infinitewindow at 12:14 PM on November 27, 2007

Agreed with box that it's the syncing that will kill this idea fast.

I'm not sure that it's even physically possible to ensure that two identical DVD players play with the type of automation you want...if "even a couple of frames" matters, wacky voltage to the player could cause the motor in one of them to spin up slightly slower, thus throwing it off. There's just no way to make this completely bulletproof.

The only completely foolproof idea I have is a radical departure: digitize both videos, put them side by side in a single video in a widescreen format using editing software, save the resulting video as quicktime or avi. Then run the thing off a cheap computer with dual monitor support, stretching the video across both. Might take some playing to get the look right, but you'd be guaranteed that the sync would be perfect (since you did it while editing). The two monitors could be separated, getting the desired (I think) effect.
posted by griffey at 12:21 PM on November 27, 2007

infinitewindow, I think is very much like what I need. The decks, for sure, will fit the bill.

From you link to the controller, this concerns me a bit:

Multiple Unit Control: VC-16b

1. Send the Same Commands to All Machines
We can supply an 'octopus' IR Emitter Cable Breakout Box to send the same commands to all machines. This is an inexpensive way to pseudo-sync several inexpensive players. This works well for short video segments because different machines will drift apart over a long time. For long-form videos that must be in exact frame sync, you should use a Pioneer DVD-7400, external 'black burst (CVBS) for sync, and a synchronizer.

My show is about 7 minutes long; do I need this black burst thing? Do you know anything about that? Does this controller not give the "true" sync I want?

Thanks again.
posted by Mister_A at 12:34 PM on November 27, 2007

I think griffey has got the right idea in general - for specifics, I think a dual-head linux box would work well. A very simple script would guarantee that the program kept repeating. Additionally, the cost involved would be fairly low, especially if you went the rental route on the monitors.


On the other hand, if those Pioneer DVD players that infinitewindow mentioned take a clock input, you can rent a clock source, sync both players to the clock source, and as long as the DVDs are the same # of frames, you'll be fine. But for someone who's not used to generating clock, that's a lot.

On preview, if that's how you're going to go, I'd say that you NEED a blackburst generator. My (semi-educated) guess is that you'd have noticable drift over 7 minutes.
posted by god hates math at 12:43 PM on November 27, 2007

griffey's idea is looking better and better...

There will be extensive A/V support on site so I'm feeling a bit better - I don't want my client screwing around with director files on site :)
posted by Mister_A at 1:02 PM on November 27, 2007

Mister_A, I don't think you will have any drift over 7 minutes with those two Pioneer machines—they really are great DVD decks. I don't remember if the RS-232 sync box we used was the same model, so check around or get recommendations from your VAR, rental house and engineers.

My instinct is that you only need black burst (genlock) sync if you intend to mix the two signals in any form, like in a video mixer or switcher. Also, you may need genlock if your programs contain different audio tracks or simultaneous jarring transitions. On the project I worked on (a 3-D loop), sync was vital, so we did use a black burst. Can't hurt!

Before he went live, the client also did a four-hour test of the program, letting it run for four hours while checking the sync every fifteen minutes. I recommend you do the same four-hour test before the show.
posted by infinitewindow at 1:06 PM on November 27, 2007

Not particularly easy without specialist hardware or software - Playing back two physically separate discs in perfect synchronisation is never going to be easy!

My suggested solution requires a PC . You state that it must be reliable and idiot proof - a laptop seems suitable as it can be lugged around with relative ease.

1/ Purchase a laptop with a relatively decent graphics chipset - something like the XPS M1330 from Dell.

2/ Purchase a Matrox DualHead2Go dual monitor interface - this is available in both DVI and VGA variations link.

3/ Use DVD decrypter (link) to rip both DVD's to the hard drive.

4/ Download the 30 day trial of Vegas pro 8 video editor (link) and use it to stitch the two videos side by side together using this tutorial here. You can then export as a single file and playback full screen using your preferred media player of choice.

5/ The Matrox DualHead2Go appears to your laptop as a single (very large) monitor but then splits this into two connections, so there should be no software problems relating to this.
posted by oliverst at 1:16 PM on November 27, 2007

Would it not be easier to change the concept than do all this?
posted by A189Nut at 1:42 PM on November 27, 2007

No, dear nut, the client is in love with the concept.
posted by Mister_A at 2:11 PM on November 27, 2007

I think it might be possible to do what you're talking about using Flash videos, but I'm not enough of an expert to know for sure.
posted by Steven C. Den Beste at 3:39 PM on November 27, 2007

I really like griffey's solution - it sounds almost foolproof. You want identical displays, and in display settings, you should choose stretch desktop, not extend. That way windows treats your two displays like one big monitor, you won't have any overlay problems (hopefully), and you can just full screen the video (a common feature of almost all video playback software).
posted by Chuckles at 9:53 PM on November 27, 2007

FYI: Playing Quicktimes on dual-display-capable machine. Thanks all!
posted by Mister_A at 8:43 AM on December 3, 2007