Bluefish444 latency & NVIDIA GPUDirect

please may I ask whether is NVIDIA GPUDirect supported with Bluefish444 I/O cards? I am looking for lowest possible video I/O latency, but I wasn’t able to find documentation on GPUDirect working with Bluefish444 in TD.

So far my experience with Blackmagic cards was far from ideal in terms of latency. AJA performed better than Blackmagic, but I am quite curious how fast might Bluefish444 be…
(In my tests total input + output delay was around 8 frames on Blackmagic Quad 2 and around 5 frames on AJA Corvid 88.)
Bluefish444 prices seem quite high, but their products (especially KRONOS K8) look very nice. Please what do you think about their I/O cards - are they worth the money? Have anyone tested their latency with TD? Thanks.


Our BlueFish support does not currently support GPUDirect, so AJA is the way to go for that currently. We are investigating upgrading the bluefish SDK and adding support for the KRONOS K8 card though.

Hi @malcolm, thank you very much for information - that would be great. While browsing Bluefish website I noticed AMD’s version of GPUDirect - called AMD DirectGMA. It looks quite interesting as it completely eliminates copying buffer to system memory. It allows Bluefish card to directly write into portion of GPU memory and also allows GPU to write directly into the memory of Bluefish card. I guess that could provide even faster transfers between cards - especially considering the fact that new AMD Radeon Pro GPUs use PCIe 4.0. May I ask what do you think about that? Is there a chance TD would support this technology in conjunction with Bluefish cards? Thanks.

I am attaching some pictures and citations.

With conventional approach, video data is copied three times in the system memory, while with Nvidia GPUDirect the data copy performed only twice (frame grabber to system memory and system memory to GPU memory).

AMD DirectGMA provides high-speed Peer-to-Peer DMA transfers between the memories of 2 GPUs or between the memories of the GPU and the FPGA. DirectGMA for Video is optimized for the likely best performance in order to exchange data between frame grabbers and GPUs with direct video streaming from Frame grabber to GPU, totally avoiding data copies to/from system memory.

Key Features of Nvidia GPUDirect

  • Accelerated communication with video I/O devices
    • Avoid unnecessary system memory copies and CPU overhead by copying data directly to/from pinned host memory
  • Synchronised transfers between GPUs and Bluefish444 hardware
    • Allow devices to work together without artificial wait-states to ensure completion

Key Features of AMD DirectGMA

Hey, this currently isn’t on our task list. Sorry

Oh, I see, all right. Please may I also ask what do you think about Bluefish cards in general? Have you done by any chance some internal tests comparing AJA and Bluefish in terms of I/O latency? I am looking for solution that would have maximum of 3 to 4 frames of total input + output delay (1080i50). However it seems to be impossible to get such a fast transfer with cards I have tested so far. I was hoping Bluefish might be better at this, but I have never had a chance to test their hardware. Thanks.

I am also very interested in this topic. I already worked with AJA und Blackmagic cards and while latency with TD was good, I found the drivers for them were buggy and in some cases even crashy.
I would gladly invest in more expensive cards like Datapath or Deltacast, but I am not sure how they compare latency-wise with AJA/BM in TD?

Deltacast support is something some clients have asked me about as well. We’re looking at assembling some money to fund the dev hours, if other people want to pool towards this as well that would be nice :slight_smile:

some major Mediaserver vendors recently have moved from bluefish to deltacast because bluefish wasn’t meeting production timetables.

Deltacast is a current OEM favourite. It’s the stock card delivered in hardware from Christie/Coolux, Avstumfl/Pixera, disguise/d3 and MA/VPU. Their FLEX architecture looks pretty neat. From what I know they are not available for consumer/low-volume sales.