About streaming using SRT

Secure Reliable Transport (SRT) is an open-source streaming protocol that offers quality, low-latency streaming to CDNs and other SRT enabled decoders across unreliable Internet connections using User Datagram Protocol (UDP) transport and additional error checking. Low-latency SRT is particularly good for real-time, two-way communications between a remote guest and a local on-site host.

You can configure Pearl-2 as an SRT source encoder and stream video using SRT. You can also configure Pearl-2 as an SRT decoder and ingest SRT streams as video inputs.

Up to six of the video inputs configured for Pearl-2 can come from SRT sources (or one 4K SRT input) and Pearl-2 can stream up to six SRT streams.

Before content is streamed between the SRT source and destination, a communication link must be established between them for SRT control and recovery packets. Any firewalls blocking the path must be traversed.

SRT streaming modes and firewalls

Streaming through firewalls can be a challenge. With SRT you get easy firewall traversal with little to no IT involvement.

SRT offers three modes to simplify the process: Rendezvous, Caller, and Listener.

  • Rendezvous mode is the easiest to setup and usually doesn't need any intervention from your IT administrator for the SRT stream from the source to traverse the firewall to the destination. The SRT source and destination devices must use the same SRT port value, see Set up an SRT stream using rendezvous mode.
  • Caller and Listener modes work together to establish the SRT connection between your source and destination devices when traversing the firewall is difficult. In this case, your IT network administrator must configure the network to allow traffic that comes in on the port configured for SRT streaming and forward the traffic to the destination device, see Set up an SRT stream using caller and listener modes.

The device you set as the Caller (or Listener) is arbitrary, as long as one device is a Listener and the other is a Caller.

SRT latency controls and AES stream encryption

SRT includes latency controls to adjust for poor network quality while maintaining an acceptable amount of delay. Pearl-2 provides statistics to determine the amount of packet loss. Using the Admin panel, you can increase or decrease the amount of latency applied to the stream to help mitigate any Quality of Service (QoS) issues. The default latency values are 125 ms for an SRT stream and 80 ms for an SRT input, see Adjust latency and view the SRT stream status.

For greater security, you can set the SRT stream to 128 bits, 192 bits, or 256 bits AES encryption. Encryption settings must be set to the same values on both the SRT encoder sending the stream and the SRT decoder that's receiving the stream, see Set AES encryption and a passphrase for SRT.