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NDI vs Capture card: which is more cpu heavy?
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andreypetr  
#1 Posted : Monday, December 7, 2020 11:04:00 PM(UTC)
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Hello. I have relatively average PC for vMX. And was wondering what capture method will have lowest impact on my system for FullHD/60 video. Does anyone have any experience comparing NDI and capture card in terms of CPU usage?
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zenvideo  
#2 Posted : Tuesday, December 8, 2020 12:56:00 AM(UTC)
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If you use a capture card that transfers uncompressed video then the CPU will probably have less to do in getting that video into the system than if it has to decompress the video (as is the case with NDI).
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mavik  
#3 Posted : Tuesday, December 8, 2020 6:50:12 AM(UTC)
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A PC is a sequential system. With videoprocessing the data is high and the time is short.
Generally I agree with zenvideo. A capture card tends to be more efficient in terms of CPU cycles.
PCI Express 3.0's 8 GT/s bit rate effectively delivers 985 MB/s per lane. FHD SDI signal we are talking of 3G/s. So you can do the math.
Decoding is more intense than encoding.

There is an alternative to sequential processing. Parallel processing. This is done with FPGA's these days. To see what is possible take a look at the 1U Ross Carbonite Ultra. A PC will never ever get to this pure processing capabilities.

With NDI you need to focus on the network as well. Not only the video side.

For simplicity take a hardware switcher and live with it's price/value/speed options. Second option for you would be HDMI/SDI capture card with video wires. Third option would be NDI. If you have good knowledge in networks that option would open a lot of possibilities as well.
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mark2020  
#4 Posted : Saturday, February 13, 2021 9:45:39 AM(UTC)
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Originally Posted by: andreypetr Go to Quoted Post
Hello. I have relatively average PC for vMX. And was wondering what capture method will have lowest impact on my system for FullHD/60 video. Does anyone have any experience comparing NDI and capture card in terms of CPU usage?


I've done a rough comparison with hardware capture, and it pushes my CPU a little more than NDI. But...that's one camera at a time, practically speaking.

If you want to have multiple cameras (especially remote based), it's worth looking into a cheap-ish second computer sending NDI to your main computer. You can program shortcuts (and/or use something like Companion) to show 1, 2, 3 or 4+ up on screen with one NDI input, so less overhead than several capture devices or added software overhead on your main computer.
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