Hyperdeck or ultrastudio: processor demands of capture?

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Adam Barnett

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Hyperdeck or ultrastudio: processor demands of capture?

PostTue Apr 26, 2022 5:48 am

Hi folks, total video amateur here. I've spent the pandemic developing a real-time graphics app as an art project, and I'm trying to figure out how I might capture the output. On my M1 Max MacBook Pro, the app runs at 2160p60, but I can't seem to get any decent software captures from the same computer producing the graphics. (Apple's ReplayKit framework is 1080p and stalls intermittently, and telling the app to write each frame with AVAssetWriter drops me to 9 fps). So it looks like I need an external capture option, about which I know nothing.

I've been looking at the Ultrastudio 4K Mini, and the Hyperdeck Studio 4K Pro, as I'd really like to capture the output in 2160p60. The US has some advantages: it's cheaper, and it has analog audio inputs. I can live with bouncing the audio through the HDMI output of my computer if I had to, so that's not a deal-breaker, but the analog ins would be preferable. I'm sure there are other considerations that I'm missing, and I'd love any suggestions about other factors I should take into account. I think the hardware H.265 encoding of the HD might have some value for me, but I expect that I'll be doing some editing together of the captured footage with some camera recordings, so possibly not - it's just something I'll have to experiment with as I go, I think.

But the one thing that's immediately not clear to me after reading the manuals for each, is what the processor demands are like if I'm trying to capture 4K video with the same computer that's generating the graphics, via the ultrastudio. There's a lot of emphasis on disk speed, which I understand, but what's not clear to me is ... if I'm straining this computer's GPU with the ray marcher, would writing the output of the ultrastudio place much additional strain? Or is it really mostly a disk operation? Is the US doing the encoding internally in real-time (albeit not the H.265 capabilities of the HD), and my computer is effectively just a hard drive host when using Blackmagic Media Express? If it's going to strain the CPU or GPU, I may need to go with the Hyperdeck and bite the bullet on increased cost.

Thanks in advance for any thoughts you have to share on this. I know dealing with amateurs is occasionally rather irksome.
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Asgeir Hustad

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Re: Hyperdeck or ultrastudio: processor demands of capture?

PostThu Apr 28, 2022 7:32 am

So the processor / GPU demands of encoding a video stream will depend entirely on your selected codec. If you select a low-compression codec like ProRes, the constraint is mostly disk speed. If you select a high-compression codec like h.264 / h.265, encoding is bound by CPU-performance (or available hardware encoders).

As an example, I used Livestream Studio this last weekend to encode a 1080p-stream, a 720p-stream, a 480p-stream and a 240p-stream simultaneously, as well as record the 1080p-stream to disk. This uses the hardware encoder on the M1 Max Macbook Pro I used, so CPU-usage (with Photoshop, Premiere, ATEM Software Control and Chrome open as well) was somewhere around 11-15%.

However, hardware encoders have limitations software encoders don't. The built-in encoder on the M1 Max is a lot worse than software libx264 for the same bitrate if you have a lot of motion or lighting changes / hard edges. It was ridiculously blocky at 16Mbps target bitrate for some of my recordings, so those I reencoded with software 2-pass export.

If you're not doing anything with the capture in real time on the computer, I'd get an external recorder and save it to a flavor of ProRes. If you need to process the video input live, get the UltraStudio.
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Adam Barnett

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Re: Hyperdeck or ultrastudio: processor demands of capture?

PostThu Apr 28, 2022 4:58 pm

That is super helpful, thank you.

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