Film-Tech Forum ARCHIVE: 4k - HD-SDI/Cinelink/IMB issues

This is topic 4k - HD-SDI/Cinelink/IMB issues 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=000743

Posted by Carsten Kurz (Member # 5396) on 02-14-2011, 05:37 PM:

Seems that with the advent of 4k DLP, the usual Twin-HD-SDI connection with Cinelink encryption is becoming outdated, because it lacks the necessary throughput for 4k.

For SONY 4k, this is not an issue, since SONYs come with their own Server/MediaBlock with proprietary 4k connections.

Aside from integrated media blocks - has anyone seen solutions for 4k playout servers for the new 4k DLP machines? Which connections are common? Are there any standards for 4k transmission yet?

- Carsten

Posted by Tom Bert (Member # 5719) on 02-15-2011, 01:55 AM:

PCIe seems to be used most today. Other -open- standards are emerging

Posted by Carsten Kurz (Member # 5396) on 02-17-2011, 09:16 AM:

I noticed that some series-II projectors have 4 HD-SDI inputs. Don't know wether they can be used together for 4k input after these machines have been upgraded to 4k. So far it seems that an IMB currently is the only option for 4k, with a dedicated PCI-e interface or something similiar.

- Carsten

Posted by Steve Guttag (Member # 268) on 02-17-2011, 11:04 AM:

NEC has four BNC inputs BUT they are used as two dual-links, not as 4 3G inputs. Remember for 4K using 292 inputs you would need 8, not 4. If they are 3G inputs then 4 would be sufficient.

The extra HDSDI inputs are handy for those that do rentals as well as broadcast grade videos so that one can leave the DCinema ports alone and plug the HDCAM in to the extra set.

-Steve

Posted by Dave Macaulay (Member # 813) on 02-19-2011, 12:30 AM:

There's an awareness that a 7m maximum length PCIe cable isn't for everyone. A multiple coax interconnect for 4K is in development. Whether this is a server-IMB connection to act much like the PCIe cable or an encrypted video link like the dual SDI between server and projector for 2K, I don't know.

Posted by Steve Guttag (Member # 268) on 02-19-2011, 07:20 AM:

The Dolby sponsored Open platform just uses the Cat 5e/Cat 6 cable as the transmission medium. Those using the PCIe cable are a proprietary format such that the IMB and server must be of the same brand...versus the Open platform...where you could have a Dolby server and a USL IMB.

It is not defined what the cabling method is in the DCI spec so it would not surprise me if the methods change as the whole IMB thing develops a bit.

-Steve

Posted by Carsten Kurz (Member # 5396) on 02-21-2011, 11:29 AM:

Here are two Doremi products dealing with 4k/IMB interfacing:

An IMB, and dedicated Player/server to connect to it.

http://www.doremicinema.com/PDF/ShowIMB3-10.pdf

- Carsten

Posted by Dave Macaulay (Member # 813) on 02-21-2011, 01:05 PM:

That Doremi brochure illustrates what the problem is. If you want your server located away from the projector - this is getting popular with the "boothless" cinema designs appearing lately - you can't use this IMB/server system. The server to projector connection is via a PCIe cable. The maximum length of a PCIe cable is seven metres. The SDI coax cables do have some maximum acceptable length but I've used many 50 foot cables with no problems. I tried 100' using two 50' cables with a BNC coupler joining them and this worked fine too.

Posted by Carsten Kurz (Member # 5396) on 02-21-2011, 03:09 PM:

Yep. It seems straightforward at first to just rip out the MediaBlock/Dolphin board from a Doremi server, slot it into the Projector and connect it through a PCIe bus extension cable.

But then PCI-e cable lenghts are limited, as you say, you still need more or less a full flegded server with a dedicated projector connection in close proximity to the projector. So, maybe from a manufacturers point of view, you gain some business with an integraded IMB deal with the projector manufacturer and subsequent server sale.

The client earns little - with the exception of 4k capability, and that's probably the only reason currently to use this IMB, because so far real 4k Playback on non-Sony systems would need 2 or 4 synced 2k servers.

That whole interface issue looks strange to me - after all, using an IMB this way means that you transfer encrypted DCP data to the IMB - that is, not only encrypted, but obviously still J2K encoded.

Which means, even in 4k, only 250MBit + audio + overhead is necessary to transfer to the IMB. Compared to nearly ten times as much with 2k/24fps/12Bit HD-SDI uncompressed over Cinelink.

So what's the big fuzz about this IMB interfacing? Why is PCIe necessary if it has this cable lenght limitations? Really seems just like a snapshot by Doremi so they could be first on the market with their 'out here, in there!' approach.

- Carsten

Posted by Carsten Kurz (Member # 5396) on 02-21-2011, 05:33 PM:

BTW - http://investor.dolby.com/releasedetail.cfm?ReleaseID=515948

'DCOSA' Open Standard initiative for IMB - server connections lead by Dolby, USL, MikroM, XDC.

www.dcosa.org

http://www.dcosa.org/files/DCOSA_Technical_Overview.pdf

- Carsten