Decklink Duo2 hardware compatibility

The Duo2 seems to be quite a popular decklink card lately due to its flexibility. I have had some mixed experience with how well the card works in various machines and am wondering if anyone else has experience similar behaviour

I ask because when I tried to use one in a i5-2500k machine, if I was to output more than 2 channels of 1080i50 via Caspar, they would all stutter, even if most of the channels had no active layers. Interestingly if I tried to output 4x1080p60 through some other software it appeared to be able to cope.
I have had another case of this with a i5-4690k, where it also cannot cope with more than 2 channels without stuttering.
Finally, I can use the card fully in a i7-7800x up to 4x1080p60.

I am wondering if its the machines I have tried are too old or did the i7-7800x work only because the card is connected to cpu pcie lanes?
Does anyone have some more sample data for any other cpu generations that will clarify what the problem is here?

What are your disk utilization like? Also check gpu, memory, and cpu utilization. If anything has near 100% then you have a hardware bottleneck other then the card. I have found reading more then two high bitrate files from a spinning drive will cause 100% active time at low actual read bit rates. Even my NVME drive has slower throughput under multiple sequential reads…

And these were all on the same driver?
I remember a thread talking about a driver update for the duo 2 fixing some things.

I know @Jesper runs these cards as well, maybe he can share the driver version he’s running them on?

@zcybercomputing I don’t think that some of those could be the issue, as for the 2500k I could get the stuttering by playing go1080p25 on a single channel, then remove a channel and restart caspar and it would then be smooth. I believe cpu usage was fine, this was something I tested over a year ago though so cant be too specific. I shall try to retest as soon as I can get back to that machine.

@mint No, these 3 machines were all used at different times, but the 2500k was attempted a couple of times most recently being I think about a year ago and that would have been with the latest firmware at the time.

The 4690 isn’t running Caspar, but in the software it is running it can cope with outputting to multiple screens, but as soon as more than 2 of the decklink outputs are used instead it stutters

You haven’t mentioned GPU’s. I’ve seen these problems GPU bound and with 2.1.x you can try:

<accelerator>auto [cpu|gpu|auto]</accelerator>

I’d guess the other software you are testing doesn’t use the GPU.

@hreinnbeck The other software on the 4690 uses the gpu more heavily than caspar, I suspect it might be gpu based right up until it interfaces with the decklink but I dont know for certain as its all closed source.
Ill try that on the 2500k later on, im curious as to if that will have any effect

Ultimately, I don’t need a fix for this issue. It would be nice to be able to use it properly in the 4690, but not essential. I am mostly wondering what the cause is and whether I can expect a 7700/8700 to be able to cope or if it is just my machines

The archery machines run 7700 with Duo2 flawlesly.

@Julusian have you tried different cards in the same machines? Might be faulty cards, do you think?

The archery machines run 7700 with Duo2 flawlesly.

And that is with 4 seperate channels not just 2 f+k?

I only have the one card available to me, so its been the same one tried in all 3 machines.

2 f+k afaik

Ive done some more testing on this now. It turns out that the 2500k is just too weak to drive more than 2 or 3 channels of caspar anyway, looking to be limited by cpu, so that machine can essentially be ignored.
I tried with a 6700T (I always forget I have access to this machine) and it is able to do 4x1080i50 smoothly.

I don’t know what this means for the 4690, but I shall do the same tests on it when I can get access to it to figure out if it can work.
But that does answer my question proving that the card is usable with recent i7s, not just the extreme series.

When you want to run multiple channels like that, core count will start to matter much more then clock speed. Assuming you have enough PCIe lanes and are CPU bound, the CPU’s with fewer cores will have a limitation with the number of channels they can run at a time. I don’t think it has anything to do with the extreme series. Doesn’t that just mean they have an unlocked multiplier and a few other extra features? That won’t make up for the fewer cores an i5 has compared to an i7.

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