Decklink Quad 2 and VMIX, various questions and troubles

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Alexander Kinov

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Decklink Quad 2 and VMIX, various questions and troubles

PostWed May 23, 2018 7:06 am

Hi all, I just installed new video system, but some of the components arrived too late and I didn't have enough time for testing and fixing troubles before the first event. Some minor problems and questions appeared and I'll be thankful for any advises.

First: the system. All components are brand new and all the software is licensed.
- Canon xf205 cameras
- All cameras are connected with the same cables
- They all go to the same converters: BMD SDI to HDMI micro converter (I use them for reclocking just in case). The SDI out of these converters go to the Decklink Quad 2 card with the same cables. All inputs of the card are set the same way.
- The HDMI outs of the converters go to ATEM switcher, which is used like a backup device, in case something goes wrong with the computer (but everything was fine)
- Computer system: MotherBoard ASUS PRIME Z370-A, CPU Intel Core i7-8700K, Memory 16GB DDR4 2400, mSATA SSD drives, NVIDIA Quadro P600 2GB Graphics (for monitors). The system is mounted in big box, suitable for rack, with enough power supply and cooling fans.
- OS Windows 10 pro

Now the questions:

1. X2 mode or X4 mode on the PCIe slot? The Board is chosen by qualified computer engineer according to Quad 2 system requirements. I have 2 PCIe slots, suitable for the Quad 2 card. I think these slots are the same, and I didn't really have time to check when assembling the system. Also, the default mode for the slots was X2. Speaking honestly I'm not really familiar with these modes, and I couldn't find useful information about which mode is good for Decklink Quad 2. However, while installing software and drivers I had to reboot few times. Sometimes the system couldn't find the Quad 2 card. Then I tried to set the slot (from BIOS) to X4 mode and I didn't experience problems so far. Is this correct? Anything else I should try/do ?

2. During the first event I noticed damaged sound from one of the cameras. Not sure how to explain it on english, but I'll try. The sound is not distorted (like the level was too high). It sounds more like there are constant drops in the audio stream. Like the signal goes on and off constantly but it happens really fast. As I said before, all cameras are the same, with same settings and same connection to the computer. I tried to reset the camera input with that camera in VMIX. It worked for a while, then the sound broke again. There was no way to try fix this during the event, so I just disabled the sound from that camera. However, this was sports event and we were using highlight repeater (in VMIX). We didn't notice any troubles with the video from that camera, but later we were checking the recorded footage from every camera and the one from this camera was with that damaged sound. I don't think the computer system is too slow - we were using much slower system before (with normal non-SSD disk drives, less memory, slower CPU) and there was no problem. The difference is that our new system has more memory and faster CPU and drives. But this time we use Windows 10, the older system uses Windows 7. One of the guys who worked wits us, said that Win 10 runs too many useless process that may slow down down the system. But checking the task manager it didn't look like the system is overloaded. And even if it was, why there is problem only with one of the cameras?

3. System freezed for a second few times. How to explain that...it looked like all cameras freezed for a moment and there was some small flicker in the video screen (feeded by one of the Quad 2 outputs). Note: the video screen was connected through SDIfiber converter-fiber cable-fiberSDI converter to avoid any ground loops and electrial problems. However, I checked the recording later and I didn't notice any drops/flickers in the recorded video. So I have no idea what was that.
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David Hutchinson

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Re: Decklink Quad 2 and VMIX, various questions and troubles

PostWed May 23, 2018 8:13 pm

I use vmix all the time (and love it) but i only use it to serve up videos and webpages to my ATEM. I would never use a computer based mixer for all the reasons you mention above. Computers are inherintly unreliable.

I know this doesn't answer your questions but my advice is swap your system around. Make VMIX the backup. You'll sleep much better I promise you.
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Dave Del Vecchio

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Re: Decklink Quad 2 and VMIX, various questions and troubles

PostThu May 24, 2018 2:08 am

1. X2 mode or X4 mode on the PCIe slot?


When referring to PCI express slots, X2, X4, X8, etc. usually refers to the number of PCIe lanes that are available to that slot. The number of PCIe lanes determines the maximum total data bandwidth available between a card in the slot and the processor or other parts of the system.

Usually a PCIe slot has a maximum number of lanes it supports and the motherboard chipset also has a maximum number of total PCIe lanes distributed across all the peripherals in the system (this includes the expansion slots as well as things like drive controllers, USB controllers, etc. that are built into the motherboard).

Some motherboards will allow you to divide the available of PCIe lanes in different ways between the different slots in the system. So if your chipset supported 16 total PCIe lanes, you could run two slots at x8, or one slot at x8 and two slots at x4, for example (what kinds of configuration are supported vary by chipset and motherboard manufacturer).

According to the technical specifications for the DeckLink Quad 2, it has an 8 lane PCIe 2.0 interface with the computer:
https://www.blackmagicdesign.com/produc ... s/W-DLK-30

So ideally you would install the card in a PCIe x8 slot, if possible. Whether you would hit the PCIe bandwidth limit if using the card in an x4 or x2 slot probably depends on how many of the SDI ports you are using simultaneously.

Each PCIe 2.0 lane has a bandwidth of about 500MB/s or 4 Gb/s. So with an x2 slot, you'd have about 8 Gb/s total bandwidth. A 3G SDI input uses about 3 Gb/s, so if you tried to use three 3G SDI inputs simultaneously in a x2 slot you could easily hit the bandwidth limit.

I'm not exactly sure what happens if you exceed the PCIe bandwidth with a DeckLink card, but I imagine the result is not good.
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Alexander Kinov

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Re: Decklink Quad 2 and VMIX, various questions and troubles

PostFri May 25, 2018 10:43 am

David Hutchinson wrote:I use vmix all the time (and love it) but i only use it to serve up videos and webpages to my ATEM. I would never use a computer based mixer for all the reasons you mention above. Computers are inherintly unreliable.

I know this doesn't answer your questions but my advice is swap your system around. Make VMIX the backup. You'll sleep much better I promise you.

I completely agree - I prefer the old fashioned way of working with real hardware and using PC for additional tasks and backup. But me and my workmate couldn't find better way - we had to find easy and relatively cheap way to add titles and highlight repeater to our production, so we did it with PC, Quad2 and vmix. Problem is - we have to provide 2 or 3 different video signals with different sets of highlights and titles. No way to do that with the switcher only (ATEM TVs HD or ATEM 1m/e 4k)
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Alexander Kinov

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Re: Decklink Quad 2 and VMIX, various questions and troubles

PostSat May 26, 2018 8:48 pm

Dave Del Vecchio wrote:When referring to PCI express slots, X2, X4, X8, etc. usually refers...

Thanks, reading your post, I think I may have done something wrong. I'll check when I go back to work and will post again.

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