Question / Help Streaming Question (4K)

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P4rD0nM3

New Member
What I Have and what I'll do:

1x - 4K monitor
1x - Capture card that can capture 4K

1. I'll play at 2160p (4K) and output it to my capture card at 4K.
2. I'll use 'Video Capture Device' in OBS and then have a custom base resolution of 1920x1080 so I can still stream at around 4500kbits.

Question:

Will OBS use my CPU to do the custom resolution converstion (2160p -> 1080p)?
 
Krazy

Krazy

Town drunk
I would leave your base resolution in OBS at the 4k resolution and then use the downscaling options in settings>video.

Also, is this capture card for a single PC setup? As in, are you using the same PC to do the encoding that you are gaming on?
 
Krazy

Krazy

Town drunk
That would be the best solution, and one that will actually eliminate the impact of streaming from your gaming rig. OBS is already as efficient as you can get with capturing, adding in a capture card messes with that efficiency since it isn't pulling data directly from the GPU anymore. And you still have to encode using the CPU on your gaming rig.

That is a sick good capture card, definitely try to use it to its fullest!
 
M

Muf

Forum Moderator
If you're using a Datapath card then you can use its internal scaling engine to deliver pre-scaled 1080p to OBS, saving on bus bandwidth and lightening your GPU load. You can also use my plugin to get the data straight from the capture card to the GPU, without having to go through system memory, but I suppose you already know that.
 
P

P4rD0nM3

New Member
Muf yep, I just wanted to make sure that I can use Datapath's internal scaling so I don't have to use my GPU. And of course! I'll be using your plugin.

Also from Datapath themselves:

Yes you can scale on the card but the maximum pixel rate through the scaler is 200 MP/s, so at that size you will some drop frames.
This may or may not be a problem for the customer depending on what he is doing.
Roughly speaking, for input mode of 4096x2160x30 (253 MP/s) you'd expect around 200/253 = 0.8 * 30fps = 23 fps at the output.
Also the reality will be slightly less than that as we have to include the frame processing overhead for NIOS, SGT's etc.
Click to expand...
 
Boildown

Boildown

Active Member
Isn't the VisionDVI-DL better than the VisionHD4 for what we do with OBS? I'd rather have one dual-link DVI than two single-link DVI connections. I'm not convinced the VisionHD4 can keep up at any but very slow framerates based on the specs.
 
M

Muf

Forum Moderator
P4rD0nM3 said:
Muf yep, I just wanted to make sure that I can use Datapath's internal scaling so I don't have to use my GPU. And of course! I'll be using your plugin.

Also from Datapath themselves:

Yes you can scale on the card but the maximum pixel rate through the scaler is 200 MP/s, so at that size you will some drop frames.
This may or may not be a problem for the customer depending on what he is doing.
Roughly speaking, for input mode of 4096x2160x30 (253 MP/s) you'd expect around 200/253 = 0.8 * 30fps = 23 fps at the output.
Also the reality will be slightly less than that as we have to include the frame processing overhead for NIOS, SGT's etc.
Click to expand...
Click to expand...

Interesting. Looks like you're damned if you do, damned if you don't:
As mentioned before, the scaling engine is limited to 200MP/s, and 2160p30 is 253MP/s.
Direct card-to-card transfer (DMA) is currently limited to aligned RGB32, which means 1012MB/s for 2160p30. Datapath cards have a maximum throughput of 800MB/s (VisionHD4), 650MB/s (VisionDVI-DL), or 480MB/s (legacy VisionRGB-E cards).

OBS2 (also known as the "redux") should make it possible to transfer in RGB24 (759MB/s) or YUV422 (506MB/s). That way you can bypass the FPGA scaling engine and use the GPU for scaling.
 
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