Blackmagic Forum

Hi folks,
We've got a weird "intermediate" setup as we've upgraded our church video backbone to an ATEM 1 M/E, but still have Canon GL-1 analog cameras. Until we can afford to upgrade the cameras, we use Analog to SDI converters at the camera locations to convert from S-video to SD/SDI. Then we run that over in-wall RG-6 to the video booth (lengths of 50-100', max). There they're converted from 480i to 720p with UpDownCross converters before ending up at the ATEM 1 M/E inputs.

Although the in-wall cabling we have is aluminum RG-6 (don't ask, long story), we do plan to upgrade eventually to fiber after upgrading the cameras, so we tested it for now to see if it would work with SDI (following the "digital either works or it doesn't" idea). Well, it does work for all but the farthest camera, which is probably around the 80-100' mark, but it was kinda weird: it worked on the Composite input setting, but not on the S-Video setting.

So I'm wondering, since allowable distance over SDI is inversely proportional to the resolution carried, and resolution really translates to amount of information carried, is the issue I'm seeing the result of S-video carrying more information than composite? Both are NTSC, but composite is over a single cable, while S-video is over two (luminance and chrominance), so since S-video is two signals, is it actually more information carried and that's why it won't transmit as far as the composite signal in my setup?

Thanks,
Jeff

Regardless of the input signal to the converter - Composite / S Video / Component, the SDI signal will be the same bitrate - 270mb/s for SD. Your problem is more likely that you are using the wrong coax. RG6? Suggests to me at first glance that you are using antenna cable. Using proper SDI cable and connectors is critical at these sort of bit rates. Belden 1505H is an example of SDI cable.

With regards to your fibre plans - why bother. SDI is good up to 300 feet if you use the right cable. Only reason to go fibre is lengths greater than 300 feet or for electrical insulation (to combat earth loop hum).

Pat

Hi Pat,
Thanks for the reply. The fiber plan was indeed for ground loop protection between the camera location power and booth power, as well as to take advantage of the Camera Converter system. The Camera Converters would allow bi-direction video and comms between the camera operators and our video booth, a step up from our current FSR radios with Eartec headphones. Headphones, great; radios, blech.

The RG-6 is in fact aluminum CATV cable...it was supposed to be copper RG-6 for baseband video transmission from our NTSC camera locations back to the video booth. However, the member-electrician who was tasked to put it in showed up and installed it before I submitted my cable specifications and the office didn't know enough to verify with me that we were on the same page. After all, he said he did CCTV installations all the time...didn't mean he knew what he was doing

When we got the ATEM system, we tried it anyway to see if it would work before we replaced all the cable with proper SDI RG-59 in hopes it would get us by until we upgraded to the fiber/Camera Converter setup. We were encouraged in that we'd previously used BMD converters to extend the S-video output of our DV tapedeck to our gym over the same cable for a projector display (S-video to SDI then back to S-video), and that worked great despite being a much longer distance. It was at least twice the length of what's causing me issue now...which is odd.

I suppose I'll have to at least replace this one run with new cabling, if not all of it. Just bugs me that I can't figure out why composite would work but S-video wouldn't. Or why this 80'-ish run doesn't work where another 150' or so run did.

Thanks,
Jeff

Have you checked the cable terminations? One bad crimp and an SDI signal can get very fussy.

kricher wrote:Have you checked the cable terminations? One bad crimp and an SDI signal can get very fussy.

I did on the camera end...well, actually I re-did it recently as when I took the cover off to replace the bulkhead connector, the cable connector came with it
I do plan to recheck the booth ends...it's entirely possible as the folks who put this cable in didn't do the greatest job.

Thanks,
Jeff