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Problem using more than 5 live HD-SDI inputs
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Joined: 6/16/2015(UTC) Posts: 193   Location: Milton Keynes, UK Thanks: 10 times
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Hi
I original posted in the General Discussion about this issue, but thought I would restart the thread in here as I still haven't found a practical resolution, and presuming my windows 7, drivers, and software are roughly the same as everybody elses, must be a hardware compatibility issue.
The situation is that I have 8 HD-SDI inputs provided by 2 x Decklink Quad Cards. I can enable up to 5 inputs as 1080i 59.94hz. Render times stay down at 2-3ms. As soon as I turn on the 6th Camera, render times jump up to 30 even the odd peek at 50ms way too slow to sustain output at 59.94fps.
Now my guess is this is more a PCIe bus bandwidth issue, as I have had 100's of inputs (stills, movies, etc..) all compositing with multi-views, and downstream overlays, scaling etc with no unexpected drops in render speed.
I am using and ASUS X99 motherboard with a 40 lane i7 CPU. The X99 motherboard has a set of lane doubler chips, that allows the CPU's to process twice as many PCIe lanes as they were designed for (i.e a 28 lane becomes a 56 lane CPU and a 40 lane CPU becomes an 80 land CPU. I'm sure there are some downsides to this strategy (for example twice as many PCIe lanes at the expense of them running at half the speed - but not sure).
What this means is my X99 motherboard has 7 full size PCIe slots (x16) and may be used as such. I am only using a total of three cards in the slots 1 x NVIDIA GFX960 (an x16 card) and the two DeckLink cards (both x4 cards). The NVIDIA Card always sits in slot 1, and slot 2 is unusable as the NVIDIA card is a dual width card. I have tried the Decklink cards in different slot combinations, ( 3&4, 3%5, 4&5 etc.) nothing made any difference. As soon as we enable the 6th SDI input, it falls over.
I have seen people claim 12 inputs of SDI on 3 x DeckLink cards on a decent platform. The X99 boards are pretty powerful motherboards, and should deal with the most demanding of tasks, so a bit confused why this may be. Somebody has suggested the architecture of the 'lane doubling chips' causes problems with the capture of video. Does anybody know any more on this?
A big thank you to anybody who can help me shed some light on this issue.
Keith
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I would bet that issiue is in RAM...its just not fast enought! I came to same issiue with 2-4 inputs...after adding more RAM (dual channel) and OC...i got more than 200% boost....its not about PCI-e lines...
I dont know how many times image go into/out the ram but you stressing BW at least 10x2Gb/s..but i assume that preview+PGM+mini screens+processing woudl add few GBs ..DDR3 1600 has only 12GB/s
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Rank: Advanced Member
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Joined: 6/16/2015(UTC) Posts: 193 Location: Milton Keynes, UK Thanks: 10 times
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I hadn't considered DRAM, but I am already using 16GB DDR4 Quad Channel running at 1086.4Mhz Not sure what I can do to make DRAM access faster, or do you consider it maybe quantity - i.e need more DRAM? I guess I should look to see if there is any paging going on when i enable the 6th Camera.
Any other thoughts?
Keith
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Joined: 1/13/2010(UTC) Posts: 5,161 Location: Gold Coast, Australia Was thanked: 4166 time(s) in 1497 post(s)
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Hi Keith,
For reference our vMix GO system has standard DDR3 memory an X79 motherboard and a Nvidia 750TI graphics card
and runs 8x HD-SDI camera inputs great!
Memory shouldn't be an issue, 8x 1080p30 signals need only 1GB/sec of bandwidth
If you see a high render time in vMix after adding that extra camera, it could be graphics related
but it seems like it could just be a motherboard compatibility issue with Blackmagic cards. (We use AJA cards in our own systems
without issue)
To test this you could try adding the cameras in a different order, perhaps trying four from the second card
then the extra two inputs from the other, or mixing it around a bit with 3 on one and 3 on the other.
Regards,
Martin
vMix
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 3 users thanked admin for this useful post.
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Rank: Advanced Member
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Joined: 6/16/2015(UTC) Posts: 193 Location: Milton Keynes, UK Thanks: 10 times
Was thanked: 53 time(s) in 27 post(s)
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Thanks Martin
I will try that. It does seem odd, as everything says I should have the performance.
Keith
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Rank: Advanced Member
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Joined: 6/16/2015(UTC) Posts: 193 Location: Milton Keynes, UK Thanks: 10 times
Was thanked: 53 time(s) in 27 post(s)
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Amazing
Instead of adding cameras 1 thru 8, I added them 5,6,7,8,1,2,3,4 and no issues. I then moved the inputs around so they were in the correct order, and still stable.
Why would this happen? I cant think logically why adding inputs in a different order would cause such a symptom?
FPS:60/61 Render Time 2ms CPU: 2%
Thanks for the suggestion Martin.
Best Regards
Keith
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Rank: Advanced Member
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Joined: 6/16/2015(UTC) Posts: 193 Location: Milton Keynes, UK Thanks: 10 times
Was thanked: 53 time(s) in 27 post(s)
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Checked the system tonight, and found we were back up to 50ms + render time. Removed one live input, and render times back to 2ms. It doesn't matter which input I remove on either card, as soon as I get down to 6 cameras all is OK. So I am one live input better off than I was yesterday - now if only I can reach seven I will be happy.
Any more suggestions, why 1,2,3,4,5,6 cameras will gine me a render time of 2ms, but 7 kicks it to 50+ ms.
Just upgraded to 16, but still the same problem.
All the Best
Keith
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I have had the exact problem, Keith. I`ve tried several different mainboards, changed graphics card, changed RAM, tried differen PCIe-slots etc. And I`ve not managed to resolve the issue.. The weird thing is that my older computer (P9X79-mainboard with i7-3930k) works like a charm with dual Decklink Quads. I`ve tried rebuilding similar systems (P9X79 and i7-4930k), but it fails. Sometimes the computers goes black and I have to do a reset to get it working again. It seems, like Martin mentioned, that it is a mainboard issue. Could you try to open vMix with 5 inputs, enable external output AND open FMLE 3.2? When I do that, the newer machines freezes. Every time. If someone manages to resolve this, that would be amazing. kgoodyer wrote:Checked the system tonight, and found we were back up to 50ms + render time. Removed one live input, and render times back to 2ms. It doesn't matter which input I remove on either card, as soon as I get down to 6 cameras all is OK. So I am one live input better off than I was yesterday - now if only I can reach seven I will be happy.
Any more suggestions, why 1,2,3,4,5,6 cameras will gine me a render time of 2ms, but 7 kicks it to 50+ ms.
Just upgraded to 16, but still the same problem.
All the Best
Keith
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