Dual Link HD-SDI

[Rafael Amador]

I found this note as well:

"Note that the data layout in dual link is designed so that the primary link can be fed into a single-link interface, and still produce usable (though somewhat degraded) video.

The secondary link generally contains things like additional LSBs (in 12-bit formats), non-cosited samples in 4:4:4 sampled video (so that the primary link is still valid 4:2:2), and alpha or data channels. If the second link of a 1080P dual link configuration is absent, the first link still contains a valid 1080i signal."
If what I pasted in the other post is true, probably that note is about 444 RGB, while this one is about 444 YUV. 422 RGB it doesn't exist.
rafael

[Aaron Newsome]

I stand corrected. I configure my camera for 4:4:4 dual link HD-SDI output. I took the dual-link SDI on my camera and used HD-SDI (1) - synced just fine and recorded it just fine. I then connected to the HD-SDI (2) and it also recorded just fine and synced just fine.

This leads me to think that two boxes could in fact be used to record a dual link signal. Now if it could be done in full 10 or 12 bits, that would be remarkable indeed.

Matter of fact, if there were a way to combine the two images, and sync the two XDR together, I think I'd buy another one. Yeah, I would.

[Jeff DePonte]

Aaron,

Couldn't an AJA Kona board handle the combining of the two legs? It would mean that you would have to play the video out in real time, capturing through the Kona as if it were being fed by a VTR.

I'm getting ready to dump my first generation Kona 2, but I see that Kona 3 still boasts Dual Link capability. Leads me to the question: how many folks with Kona boards ever actually used Dual Link input?

I've also begun wondering about the nanoFlash's potential as a DDR, and whether or not it might (with some work, of course) be controllable by RS-422 protocol.

Interesting, fun stuff to consider...

Jeff

[Aaron Newsome]

Interesting points Jeff. If I had a Kona card, I'd be using dual link input everyday since may camera has dual link output. Not sure how many people use it though.

I was thinking more of a software method to combine the two seperate recordings of single link from a dual link source. Playing them back on the XDR or Nano doesn't provide me with any comfort level at all. These boxes have been proven to have severe playback problems. Maybe once they are made to be reliable playback boxes, this would work.

This has me even more curious now though. In order to test it, I'd need another XDR, a way to sync them up for recording and locked playback, a PC, a kona card, a RAID. I guess I'd need a lot of stuff.

I really would like to know if it would work though. At a price of around $8500 for two XDRs, it would be the lowest priced portable 4:4:4 recorder that I know of.

To be really useful though, the RS-422 port would need to be active, another feature that I'm not counting on anytime soon.

[Rafael Amador]

As I see the things, it would be a possibility of recording 1080p60/50 YUV 422.
No 444 RGB or YUV.
In 1080p60/50 YUV 422 its seems that each SDI output a 1080p30/25 stream. One the odd frames the other the even frames.
If you are able to record those two streams (Intraframe recording) combine the would be really easy with AE.
You don't need two NANOs to test if this is feasible.
Try one SDI at the time. See if you are able to record anything.
rafael

[Douglas Call]

Originally Posted by Aaron Newsome

Hi Jeff, I also have a dual link SDI camera and I'm pretty sure that the Nano will not sync to a leg of a dual link output. I can test this tomorrow to be sure.

I noticed you said you have a dual-link SDI (SMPTE 372M) compatible camera, what kind of camera is it. I have been trying to find a link to all the professional camcorders that support SMPTE 372M or SMPTE 424M with zero luck.

[Dan Keaton]

Dear Douglas,

Arron has a Thomson Viper.

[Aaron Newsome]

Dan is correct, it is a Thomson Viper. Since my original post, I did in fact purchase a 4:4:4 recorder and I now use that recorder when I record 4:4:4 dual link, and I use my Convergent Design recorder when I want to record 8bit 4:2:2.

You'd be surprised how often 8bit 4:2:2 is really all you need, although it's nice to have the option to do either.

[Mark Job]

Originally Posted by Aaron Newsome

Dan is correct, it is a Thomson Viper. Since my original post, I did in fact purchase a 4:4:4 recorder and I now use that recorder when I record 4:4:4 dual link, and I use my Convergent Design recorder when I want to record 8bit 4:2:2.

You'd be surprised how often 8bit 4:2:2 is really all you need, although it's nice to have the option to do either.

....Hi Aaron: I'm sure that a Thompson Viper is worthy of at least 10 bit minimum color precision ;-) Although I'm sure the XDR clips look utterly amazing !

[Douglas Call]

Originally Posted by Aaron Newsome

Dan is correct, it is a Thomson Viper. Since my original post, I did in fact purchase a 4:4:4 recorder and I now use that recorder when I record 4:4:4 dual link, and I use my Convergent Design recorder when I want to record 8bit 4:2:2.

Thanks for your guys answers.

I just noticed while looking through the user manual for the Viper the following supported formats:

The following formats can be selected in the Install menu:
1080psf at 23.98Hz
1080psf at 24Hz
1080psf at 25Hz
1080psf at 29.97Hz
1080i at 50Hz
1080i at 59.94Hz
1080i at 59.94Hz - 23
720p at 23.98Hz
720p at 25Hz
720p at 29.97Hz
720p at 50Hz
720p at 59.94Hz

What really surprised me was that even with the dual link data transfer rate the Viper doesn't appear to offer 1080p at 59.94Hz? I must have had the wrong impression about the reason for dual-link SDI to start with. I though it was introduced to be able to support the 1080p 60fps data rate. I'm seeing this isn't stricly true. Obviously the quality you must be getting is really incredible even at 1080i so I guess it's not really a problem. Since it looks like this camera is a Digital Cineman camera your probably shooting at 720p @ 24fps.

One thing I did notice when looking at some specs for SMPTE 424M standard is that it does mention it supports the 1080p @60fps data rate. In addition of course it offeres the dual-link SDI data rate to be transmitted through a single SDI cable at 1080p @ 60fps
http://en.wikipedia.org/wiki/SMPTE_424M


So I guess I'm back to my orginal question which is if any manufacture offers dual-link SDI or 3G-SDI on a camcorder (one piece unit) for 1080p @ 60fps capture?

Note: I guess you'd be generating some pretty big files at almost 3G/s second. Do you archive the big files to LTO-5 and use 16G/b Fiber Channel or 10GbE LANs to move the big files around?

[Mark Job]

Hi Douglas:
The reason for dual HD-SDI is to effectively transmit the 4:4:4 color space signal, which is 50 % greater than standard broadcast wavelengths.

[Douglas Call]

Mark's Response:The reason for dual HD-SDI is to effectively transmit the 4:4:4 color space signal, which is 50 % greater than standard broadcast wavelengths.

Thanks for that bit of information, now it's all starting to makes more sense to me. So conversly when they're talking about the new SMPTE 424M standard supporting 1080p @ 60fps over a single SDI cable that would imply you'd be able to transfer video upto a 4:2:2 color space. Does that sound about right?

If not then now I guess I don't understand what the new SMPTE 424M standard is for :-)

[Mark Job]

Hi Douglas:
3G HD-SDI is simply a 3 Gigabit wide Interface which will allow a 4:4:4 bandwidth video signal to pass through a *Single HD-SDI interface, instead of having to use two (2) HD-SDI sockets to deliver the wider bandwidth video signal. (This would save space and money on a SSDR box [Like Mine] if I ever finish it !). A 3G HD-SDI interface is backwards compatible with standard broadcast HD-SDI 4:2:2 bandwidth signal interface.

[Douglas Call]

Hey Mark,

Here is where I got that info from:

http://www.extron.com/download/files...sdihdmi_ts.pdf

Basically if you scroll down a little once you navigate to the page you'll see under
Mapping Structure One is you get:

1920 x 1080 4:2:2 (Y’C’BC’R) / 10-bit 60, 60/1.001, 50 frame progressive

So I miss assumed that I could shoot 60fps @ 1080p. using the 3G path.

[Mark Job]

Hi Douglas:
You certainly could shoot 1080 p 60 over 3G in 4:4:4 12 bit color space precision, as long as your camera can output this rate. The Sony SRW9000 HDCAM DR camcorder does precisely thus.