Latency is very low now...

[alatteri]

Hi UG community.

I wanted to show how low the latency is with the latest version of UG. I've recently done a fresh install of Ubuntu 22.04 Server on our encoder and receiver.

The encoder is an AsrockRack 1U2LW-X470 with DeckLink 4K Pro using x265 with default settings.
The receiver is an Intel Nuc12i7 with UltraStudio Mini4K.

The encoder sends a single stream to a cloud LXC container running Hd-Rum (UG Reflector). The reflector then splits the stream and sends it to the receiver(s). This allows us to reduce office internet bandwidth to a single stream, and burdens the heavier bandwidth onto the cloud if there are multiple receivers. All streams are SRT wrapped for resiliency.

[DeckLink In--> UG Encoder --> SRT Transmit]--> (cloud) [SRT Receive--> HD-RUM (reflector)--> SRT Transmit]--> (receiver)[SRT Receive--> UG Receiver--> DeckLink Out]

Input is 2K SDI 12bit RGB444@24fps. Inherent latency from the SRT wraps was around a total of 80ms, and even still, look at the image below. The bottom is the monitor on the SDI source machine, and the top is the output of the receiver, only 8 frames, about 328ms difference. In this example, the encoder is connected to our 1gig fiber internet link, and the receiver is connected to our 250mb residential coaxial internet backup. Very similar to the performance someone would get at home for their receiver. Stream data load varies between ~10mb-30mb/s dependent on video content.

In this scenario, the SRT wraps add about 2-3 frames of latency. As the RTT of the receiver increases, so will the delay. I currently use a 3x multiple of RTT when calculating the SRT latency setting. I've never had good success with UG FEC and x265. Although it has been about 2 years since I last tried with x265, it worked great with x264 though. SRT also has the ability to do its own FEC, and I've never been able to get that working properly either.