PDA

View Full Version : split SDI?



Jake Wilganowski
10-03-2014, 06:34 PM
Has anyone ran a simple sdi "T" splitter out of the epic's sdi port with success and no noticeable signal degradation?

Alexandros Tsoupras
10-05-2014, 12:19 AM
I have use it. No problem at all.

Björn Benckert
10-05-2014, 02:35 AM
A T-splitter will for sure cause problem if the cables are long. It' might work for having two SDI things rigged on camera. But much better to use such items that has a loop trough or built in splitter, or just get onr of these no active splitters: http://www.belden.com/blog/broadcastav/Splitting-Digital-Video.cfm

Gunleik Groven
10-05-2014, 02:45 AM
T-splitters to director/client monitors can indeed cause issues. Björn is right!

Remo Fritzsche
10-05-2014, 02:50 AM
I'm using a T-splitter all the time. A very short cable goes to my Alphatron EVF, and a 20m cable to the director's monitor. Never had any issues. This setup has been verified with the BMCC though.

Jake Wilganowski
10-05-2014, 10:32 AM
Ok thanks everyone. One side would be going to my action products SDI wireless transmitter module and the other would go to my camera monitor. The problem I'm trying to solve is when I pull the Anton Baur battery off it kills the SDI loop through on the Action Products unit, so If I get a splitter I can have a redvolt in the sidehandle and keep my monitor feed and camera powered on as I change out Anton bricks

Björn Benckert
10-05-2014, 10:58 AM
I'm using a T-splitter all the time. A very short cable goes to my Alphatron EVF, and a 20m cable to the director's monitor. Never had any issues. This setup has been verified with the BMCC though.

I think then you are lucky with those two cables as the issues are caused of the wave length of the video signal and the difference in cable length. If you are out of luck the video signal might get out of phase and partly bounce of from one device and disturb the other. In HD video world that works and all is good normally, but then all of a sudden you get no signal. Some times it's enough to get a bend on the cable or such to get out of wave length and lose the signal. So I would not, even if it works now and has worked all the time before, be depending on such setup as like everything else it stops working only when you really need it....

My example, On a shoot I was having a video feed from the Milo to a T connector, where one cable went to my monitor and looped trough to directors screen. The other half of the split went to the video bay... On the rigging day all works without any issues, on the rehearsal day it works without any issues. On the shooting day.... ofcourse we loose signal just when we are about to shoot... then it comes back, then we loose it again ,then we swap cable and it comes back... then we loose it again... then I dig around in my cases and find a SDI splitter and problem is solved. So basically if there is video issues... then T connectors are the first thing to take out of the equation. Even A T- connector with nothing on one of the ends is a bad thing, I been told that then you need to put on a small resistor on the empty end to make it work as a good straight connector.

Black magic are selling BNC splitters so I think it's if they say it's no problem splitting with just a T connector then thats a bit mad...

Here is the better explanation copied from the Belden web page:

" While you might get by with a BNC 'T', this would cause a mismatch on the two splits and could result in some reflected signals.
By the time you are talking about HD video, the quarter wavelength is just slightly above one inch, so everything is critical. The only way you can split this signal, without really horrible reflections and return loss, is with an impedance-specific splitter. A lot of engineers might tell you this can only be done with an active device (i.e. an HD-SDI distribution amplifier), but that's not true anymore. There are passive HD splitters out there."

Gunleik Groven
10-05-2014, 11:10 AM
Björns experience closely reflects mine...

Björn Benckert
10-05-2014, 11:19 AM
Björns experience closely reflects mine...

He,he... Me on the Pre prod meeting. -"Why would we need a video assist? we got so much time and I can set that stuff up easily, even long before we shoot...." And then while shooting in the middle of nowhere I learned about splitting HD video.. lol.