NDI to SDI output with Caspar


#1

Hello,

I want to use Caspar with NDI in studio environment, in order to avoid DeckLink cards in a server. The goal is better mobility and easier maintenance. I know I can also use DeckLink Studio mini:
https://www.blackmagicdesign.com/products/hyperdeckstudiomini
but it imposes using Thunderbolt which in turn causes it’s own set of demands on a setup, and makes it less universal.

However, when I searched for the device which can decode two channel key + source NDI stream to two SDI outputs turns out there is no such device on the market. Next option, I guess, is to route key and source to two separate channels with some gymnastics to two single channel NDI decoders, but these decoders are hard to find, I see two options:
https://www.bird-dog.tv/studio-ndi-details/
https://www.magewell.com/products/pro-convert-aio-rx

Both devices are US$ 690 per piece, so it’s a bit expensive to experiment without knowing if someone did this before. Have some of you guys tried these setups? How are your experiences using pure Caspar software server setup with NDI and external devices in studio/OB environments?


#2

In my, limited, experience, I would always prefer a Decklink card over any gymnastics with NDI. It‘s much more stable and uses less resources. What is the reason that you want to avoid Decklinks?


#3

Why I would like to avoid DeckLink card in production server:

  • more rack units occupied if proper cooling is implemented, reducing mobility of the unit if needed to be transported to OB or different setup. Worked with raiser cards and custom hardware setups many times before, do not particularly like them.

  • need for proper driver to be re-installed or updated in case of system reinstallation due to some catastrophic failure

  • adding one additional point of failure inside of server, instead of having dedicaded NDI converter device outside of server. Also complicating troubleshooting for someone not knowledgeable with DeckLink specifics

I’m not saying anything of this is critical, but modern processors can easily generate two NDI streams. There are NDI implementations even for ARM devices, so modern Intel processor is just fine with this task, and it’s sitting not much employed n our Caspar boxes anyway, all the work done by the graphics card.


#4

I would like to comment on your points. Just to help you find the right solution, not to tell you, that I know better :smile: OK: A little bit…

I see. That is true for the most cards. I don’t like riser cards also. But now there is that new Duo 2 Mini, that fits upright in a 2 RU case (low profile slot) and give you two fill and key or one fill and key, an input and a preview.

You also need to reinstall NDI drivers etc. I would try with a hard disc imaging tool, like Acronis True Image or the like.

Also agree. But you add a lot of external boxes with cables and power adapters etc. to the NDI setup.

I talked to the Bird-Dog guys at IBC two years ago, when they first popped up, that we need a proper NDI output box with fill and key. But I think they never catchd, what I was talking about. I personally don’t like the “External_Separate_Key” setting in Caspar, as I am newer sure, if the two outputs REALLY are in sync and stay in sync for a longer time. So a box that could do NDI fill and key output would be a fine thing, also because it uses less network-bandwidth to send a fill / key, than to send two full signals. But without such a box I think it‘s a bit a hacky solution.


#5

Thanks, didn’t know Duo 2 Mini fits in 2 RU, it’s a good improvement over Extreme card. And I understood that key & fill are tested to be perfectly in sync.

While I followed your link on DeckLink site, there was also this little miracle there:
https://www.blackmagicdesign.com/products/decklink/techspecs/W-DLK-35

It even has a reference in. I wonder if these two other connectors can be configured to be two outputs, and are they in sync?


#6

FYI I have plenty of 1U Supermicro servers with low profile quadro cards and decklink extremes/duos/quadros in OB trucks for Caspar.


#7

@hreinnbeck
Hijacking the thread to ask what LP quadro cards are you using and what’s the performances like? Eg: how many channels, resolution, etc

Thanks!!


#8

IIRC It’s mostly Quadro 2000’s. They all run 1080i50 - never done more than 4 channels, no performance issues. Will double check after the weekend.


#9

I did not figured out, if the two BNC’s are one input and one output (the 3rd is the reference) or if they can be used as two outputs (or two inputs) as the connectors on the Duo 2 and Quad 2. It only says that it can record and playback simultaneously, what let me expect it to be fixed to one input and one output.


#10

My little experience after one year testing ndi in a little studio.
We are producing some news programs.

Pros that i found:

  1. Motherboards without free pci ports. You can use ndi yet.
  2. More than a signal over one ethernet connection. In my opinion no more than 4 maybe 5 signals. The bottleneck is the gigabit interface.
  3. Bidirectional interconnection over one ethernet cable
  4. Simple signal monitoring with NDI monitor.
  5. Versatile distribution using A GOOD Giga ethernet switch is cheaper than the same size hd-sdi matrix.
  6. It not so easy BUT it is possible to route ndi signal in a MAN network. I was testing that now.
  7. The cost for a complete infrastructure is lower than hd-sdi.

The cons:

  1. The delay exist, in each connection and you must consider that. May be really a few frames but …
    think about it, this problem is accumulative.
  2. Really ndi consumes more cpu resources than a hd-sdi video board.
  3. The ethernet cabling MUST BE EXCELLENT. Bad cables or conectors produces frame rate errors.
  4. It is not a good idea to use the ndi network for other use than ndi. If you can, use a separate switch.
    Thank you.

#11

And i forgot to mention. Ndi for arm devices is like the unicorn for me. I can’t find a practical application. Please link information if you know about it.
Thank you again.


#12

Thanks macbab for first-hand experience.

Practical application for ARM NDI device would be a simple external monitoring outlet on HDMI interface of modern Raspberry Pi, which should be powerful enough for decode. We know that software exists and works on better mobile phones, but no one has the source code as far as I know.


#13

Mainly, as @itod states, ARM can help to receive NDI signals on HDMI monitors.
NDI hardware decoders are just beggining to appear (as http://www.magewell.com/products/pro-convert-for-ndi-to-hdmi) they’re reliable but expensive compared to a SFF PC or a ARM box.
I’m using NDI on my productions since 2015, do not hesitate to ask for help on that topic.