In this blog we demonstrate the difference between NDI®|HX and the HDMI output of our AV-CM70-NDI camera, available in black and white. We’ve taken a single camera, connected the HDMI to a Black Magic Decklink capture card, and connected the LAN port of the camera to a Netgear switch for the NDI® stream. The PC used to record this is connected to the same switch and runs VMIX as the recording software to be able to put both the HDMI from the capture card and the NDI®|HX stream next to each other for comparison.
The laptop used to display the test signal is running at 120fps (its display can run at 144 fps) and is running a test screen at 120fps, showing 120 squares. It loops through all squares each second. 1 square equals 1/120th of a second, which is roughly 8.33ms per square. You can pause the video at any time and see the exact amount of squares the NDI®|HX is behind the HDMI capture. As you’ll see, this is always around 4 squares, so 4 x 8.33ms = 33,32ms or 0.033s of latency compared to an HDMI capture.
This only shows the offset between an HDMI capture card and the NDI®|HX stream in VMIX. Independent tests have shown that the AV-CM70-NDI is capable of delivering video with an end-to-end latency of about 83ms in total compared to ‘live’. This also brings to light an interesting fact; HDMI, or SDI for that matter, is not without latency itself. There’s latency in the camera, the signal needs to be processed internally, there’s latency on the capture card, the signal needs to be converted there as well and there is latency on the display used. This last bit of latency is known as input lag and varies widely between high-end PC screens (from 2ms) to lower-end TV’s (even as high as 80ms). Latency-free video does not exist in our world.
CM70-NDI – Endless possibilities
The CM70-NDI includes a rich feature set known from the CM70 series and has the ability to deliver outstanding quality even under low light conditions. The combination of a high-quality PTZ camera with a protocol that improves every live production give the CM70-NDI endless possibilities.
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