This is topic Toslink connection through DMA-8 in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.


To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=16;t=000501

---

Posted by Kyle Butler (Member # 5601) on 02-03-2010, 08:48 PM:
 
We have second run shows coming up this summer. and chances are, we'll only have one lonely 35mm projector left.

Details are limited at the moment, but as far as it seems, our
booker will handle the licensing to play blu rays/dvd's etc.
However, no solution as to what kind of setup will be used has been discussed.

has anybody tryed to use the optical input on the dma8?
What kind of results did you get?
I could always use the external 6 channel, but that would be another piece of equipment to deal with.

and has anybody found any decent SDI input switchers that have worked?

it works just fine with an HDMI to Dual SDI scaler straight into the projector, but it would be a hell of a lot more convenient to not have to make disconnections nearly everyday.

all of our digitals are 2500s's by the way.
Ive seen similar posts like this, but none for NEC.

Thanks!
 

---

Posted by Sam D. Chavez (Member # 1841) on 02-03-2010, 10:26 PM:
 
I've used the Toslink several times and it works great with no hum issues that may pop up with the coax input.

As to using HD SDI switchers, I don't think you can maintain Cinelink encryption using a switcher, at least not an active one. You can always use a passive patch bay.
 

---

Posted by Stephen Furley (Member # 1277) on 02-04-2010, 01:59 AM:
 
I've used it several times from my laptop for normal two-channel PCM and once with Dolby Digital; works fine. Unlike more conventional fibres it's only intended for short distances; avoid very long cables, the one I was using was only three metres. Use decent quality cable and avoid very tight bends in it. If possible, use a single length of fibre, avoid passive couplers and cheap repeaters and fibre/co-ax converters. If you have a long distance, greater than say ten metres, try to move the equipment closer together, if you can't do that consider using co-ax, and if you have to convert between the two use a decent converter.

The Toslink interface carries data in the S/Pdif format, which is exactly the same as he co-axial one. As far as the audio data are concerned it's also the same format as AES, it's only some of the metadata that differ between AES and S/Pdif, though S/Pdif doesn't have to support the highest sample rates, but often does on later equipment.

The AES3id inputs on the DMA8+ (Digital 2 and 3) will also accept co-axial S/Pdif connections via a simple phono-BNC plug adapter. The 75 Ohm impedance is correct, and they will accept the S/Pdif format matadata. The Voltage is lower than for AES3id, but on short runs this won't be a problem, so you can connect players with either optical or co-ax outputs to the DMA8+; I've done both.

I've used DVD with a NEC projector, NC800c, but that was with analogue component output via a Christie Cine IPM 2k to the DVI input on the projector; again, worked fine. I've no experience of Blu-ray, nor of connecting via SDI. For my laptop I used a DVI connection to the Cine IPM; again worked fine, and with 1080p material the results were surprisingly good, not far short of true digital cinema material, though this was with a very small screen. I ran a few trailers this way hen we didn't have a 35mm copy.
 

---

Posted by Steve Guttag (Member # 268) on 02-04-2010, 08:47 AM:
 
Cinelink should not be affected by an SDI switcher. There are many brands for that but they are going to be expensive since SDI is a broadcast medium. Popular brands are Evertz, Harris (Leitch)...and now Extron has gotten into the market.

The Barco ACS2048 is a good addition to any DCinema system to add A/V inputs to a DCinem projector using the DCinema's DVI input(s).

And yes, the Toslink on the DMA8 works just fine.

Steve
 

---

Posted by Sam D. Chavez (Member # 1841) on 02-04-2010, 09:27 AM:
 
I went through this HD SDI issue last year while doing this Academy of Science project.

We were told by Paul Zoesky and Stuart Bowling of Dolby that you cannot use an active switcher without breaking the cinelink etc.

We ended up using a passive patch bay. I have not actually tried using an active switch. I believe this is prohibited by the DCI spec's.

Think about it though, would it not be cool to be able to have a HD-SDI switcher that routes the cables from each server to your choice of projectors in a multiplex. You would not have to move the content and be able to switch screens in an instant.

But you can't.
 

---

Posted by Carsten Kurz (Member # 5396) on 02-04-2010, 04:53 PM:
 
There are certainly differences between active SDI switchers. Some 'passive' ones might only use coax-relays. Some may simply replace coax relays by electronic switching, but will not touch the signal at all, so both will be transparent to CineLink Encryption.
Other, more advanced switchers might actually fool around with the data in the signal. Or they will not only switch, but distribute the signal to multiple sources, which will break Cinelink as well I guess.

- Carsten
 

---

Posted by Steve Guttag (Member # 268) on 02-05-2010, 09:59 AM:
 
I'd be more than amazed if an active SDI switcher broke the Cinelink. The switcher is nothing more than a repeater and clocks data in, clocks it out...the signal is unchanged. Now if the SDI like is somehow being used in a bi-directional manner (not SMPTE compliant) that would be the only way an active switcher would have issues. However...the issue I could see is that you have to have the server also communicating with the right projector on the Ethernet side to keep the link. So...just switching the video (SDI) would not be sufficient, the Ethernet and subsequent MAC/IP addresses must also match.

My desire to have the SDI ports on a switcher is to allow the SDI ports to be used by either DCP OR a local HD VTR (HDCAM SR).

Next time the opportunity presents itself, I'll definitely give it a test.

I wonder if they gave you a REASON the link would be broken. It was kinda like the 50-foot thing on the SDI cables...I always wondered WHY they needed that...I know the potential result were SDI errors but a properly designed system that follows SMPTE standards should not require a minimum length.

Steve
 

---

Posted by Sam D. Chavez (Member # 1841) on 02-05-2010, 08:43 PM:
 
It's all mere speculation until you try it. Steve is being logical and sometimes it's not about that.

Funny, no one has tried the active switcher yet.

BTW, I would never have believed the 50 Ft. cable myth until it happened to me with cables made by Lonny no less, speaking of mythical.

We were getting high TI error rates in the log and I finally went in and changed to 50 Ft. cables to go all of 2 Ft. as the crow flies and the problem went away.
 

---

Posted by Brad Miller (Member # 2) on 02-06-2010, 12:02 AM:
 
Geez Sam, just stop using high quality Lonny cables and go buy some short cheap crappy cables from Radio Shack.
 

---

Posted by Steve Guttag (Member # 268) on 02-06-2010, 02:35 AM:
 
On the cable thing...I've done shorter than 50-foot...no problems (DSP100/DSS100 connected to a CP2000-SB).

On the active switcher thing...I've had DCinema going through an active switcher (Leitch and/or Miranda) without issue...I'm trying to recall doing that with anything in recent memory where the current encryption methods are used...I don't think so...all temp setup have been direct and theatre set ups are direct...it would be in one of my "fancy" rooms that a switcher could come into play.

Steve
 

---

Posted by Stephen Furley (Member # 1277) on 02-06-2010, 03:45 AM:
 

quote: Sam D. Chavez

---

BTW, I would never have believed the 50 Ft. cable myth until it happened to me with cables made by Lonny no less, speaking of mythical.

---