Film-Tech Forum ARCHIVE: SDI cables.

This is topic SDI cables. 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=001597

Posted by Stephen Furley (Member # 1277) on 08-13-2013, 03:58 PM:

Can SDI cables be used for analogue component and composite video?

Posted by Pete Naples (Member # 761) on 08-13-2013, 04:21 PM:

Short answer - yes.

Posted by Bruce Hansen (Member # 281) on 08-13-2013, 06:50 PM:

I second that answer, yes you can. SDI cabeling is better at handeling high freqs, and has better shielding than good old RG-59.

Posted by Gialoc Do (Member # 7787) on 08-13-2013, 09:03 PM:

Posted by Stephen Furley (Member # 1277) on 08-14-2013, 04:14 AM:

Thanks for the replies. Not using SDI at the moment, but almost certainly will need it at some point, so will buy SDI type cable now.

It seems to be either white, or a light blue, similar colour to the aqua sheath on om-3 multi-mode fibre. Is there any difference between the two colours?

Posted by Scott Norwood (Member # 30) on 08-14-2013, 12:24 PM:

Purple seems to be common for HD-SDI runs in installations (at least on this side of the pond), but the color of the cable insulation doesn't matter. Belden 1694A comes in a number of colors, as does the Canare equivalent.

Everyone who has posted here probably knows this, but I will mention it anyway: when running cable for component analog video, the cable runs for a given signal all need to be the same length. Same for Y/C (S-video).

Also, for whatever it's worth, SDI cable works fine for AES audio.

Posted by Bruce Hansen (Member # 281) on 08-14-2013, 04:51 PM:

Most cabeling today is avbl in the ten colors of the "color code" (same as resister color code, except that black = 10 in cable color code and 0 in resister color code.

Brown = 1
Red = 2
Orange = 3
Yellow = 4
Green = 5
Blue = 6
Violet = 7
Gray = 8
White = 9
Black = 10

I see a lot of people using 1694A type cable for short runs. This is silly. 1694 is big, stiff, heavy, expensive, and hard to work with. For short runs use 1855A (or Gepco VDM-230). It will transprot HD-SDI up to 200 feet. 1505A (RG-59 size)(or Gepco VPM-2000) is good up to 300 feet. 1694A is good up to 340 feet. DO NOT distort the cable dimentions with tight bends or tight tie raps, or walking on it or running things over it. This can cause the cable at that point to change impeadence, and that will cause problems due to the short wavelengths involved. To be safe, derate the distances a little, that I gave you above.

Just to be clear 1505A is NOT the same thing as the old RG-59 type cable 8241. But 1505A is the same size as RG-59.

Posted by Steve Guttag (Member # 268) on 08-14-2013, 09:54 PM:

We use 1694A for most all 75-Ohm coax needs (even short runs)...why? Because we are not going to tool up for every cable on the planet. Some of our SDI runs are long, some aren't. We have two spools on hand at all times (Red and Green). The difference in cost of the various types at a 15' run just doesn't justify adding another spool (or 2) of the smaller cable. Whereas it is a "fixed" installation, the size/stiffness just isn't an issue either.

It is all getting to be pretty moot in DCinema though as almost everything is on IMBs which negate the need for SDI in cinema (unless you have broadcast sources like HDCAM...and we do). Conventional analog video is also almost dead.

Posted by Stephen Furley (Member # 1277) on 08-16-2013, 02:33 AM:

Steve,

I've never seen the newer systems with IMBs; I've been out of projection for over three years now. How do the data get into these systems id they don't use SDI? What exactly is a IMB anyway?

Posted by Sam D. Chavez (Member # 1841) on 08-16-2013, 09:41 AM:

IMB stands for internal media block. This means the encryption/decryption function takes place inside the projector chassis instead of inside the external server. So in this arrangement the server just holds and manages the content and sends the data on Ethernet cables to the IMB.

There are now IMS's on the market; Internal media server or some other similar name. Same functions as IMB but in addition there is storage to hold the "print" is held in the IMS. This allows for lower cost external storage devices to be used so ultimately this will enable lower cost D Cinema.

Problem is, most cinemas have already converted using the technology available at the time.

Maybe next time.

Posted by Brad Miller (Member # 2) on 08-16-2013, 07:40 PM:

I'm still not sold on the idea of putting the hard drives on the IMB and the placing that in a projector.

Posted by Sam D. Chavez (Member # 1841) on 08-16-2013, 08:28 PM:

I don't disagree with Brad but it seems to be moving in that direction.

Maybe when there are solid state drives at a lower price point it might not be as much an issue regards heat and vibration.

Posted by Brad Miller (Member # 2) on 08-16-2013, 09:27 PM:

It will be an issue of storage space though for a long time. It's just not a good idea.

Posted by Steve Guttag (Member # 268) on 08-17-2013, 12:13 AM:

They also need to get these IMS/IMBs to the point where one can just shut the projector down without having to FIRST shut the server down. At least one brand's IMB system doesn't care if the projector with the IMB is shut off and the server itself is kept running.