Secure Reliable Transport in Premiere Pro

How does SRT work?

SRT, a video streaming protocol based on User Datagram Protocol (UDP), enables users to stream video and audio packets of information from Premiere Pro to different viewers. As the viewer receives them, there is acknowledgment information about the reliability of the stream exchanged between Premiere Pro and the viewer.

The SRT stream always operates at the same video stream parameters as the Transit Output (Frame Size, Frame Rate, Sample Rate, Mix track Channelization, etc.)

What makes SRT secure and reliable?

SRT has optional Advanced Encryption Standard (AES) Encryption, so the video and audio stream is secure. This makes SRT more secure than some other network streaming protocols.

The data sent from Premiere Pro is broken up into discrete packets of information and transmitted sequentially to the viewing client application. If there is any data loss (due to network congestion or poor network performance), the viewing client can request that packet be sent again  - maintaining the continuity of the stream.

SRT is better able to send video data without interruptions on poor or slow networks. A certain amount of latency is always added to the SRT stream, allowing time for the two SRT endpoints to receive, acknowledge, and then resend packets of data lost over the network.

The end result of the packet verification system is less video and audio loss when transmitting over the network, at the expense of some level of latency between the sender and the receiver.

How to enable the SRT stream

Enable the SRT stream in Premiere Pro by doing the following: 

What modes can I use with SRT?

The SRT protocol involves a handshake between Premiere Pro and the viewing client. Once a valid handshake has been established, the video will be sent from Premiere Pro to the viewing client. A valid SRT connection can be made using three distinct modes:

How are the streaming modes connected?

Different modes are selected based on various factors. Here's how they all work together:

Listener and Caller Mode

Listener and Caller modes work together when making SRT streaming connections. To make a connection with these modes, there must always be one Caller and one Listener. These modes work together as a connection pair.
The Caller will initiate the handshake to a Listener, and establish the SRT connection, regardless of the direction of the video signal.

Premiere Pro can operate as either a Caller or a Listener, even though Premiere Pro can only stream video and audio out (Premiere cannot receive or ingest an SRT video stream). The Mode is just for the establishment of the stream, not for the direction of the content stream. Video will always be sent from Premiere Pro to the viewer. Once the SRT connection is made, the modes are no longer relevant. 

Modes are selected depending on network configuration, Viewer configuration, or other streaming configurations, such as connection Premiere Pro to a dedicated SRT ingest server.

Multiple Premiere Pro workstations are being connected to a central SRT Routing server. A possibly efficient way to manage such a configuration is to place the Premiere Pro workstations into Listener Mode and set the SRT server to Caller Mode so adjustments can be made to the centralized SRT Server.

Conversely, if a set of Premiere Pro workstations are not regularly set to connect to a central SRT server, the server could be set to Listener Mode to receive any connection from a Premiere workstation without having the IP address for each central SRT server. These streams can be identified by the Stream ID parameter to the server.

Rendezvous Mode

It's a peer-to-peer method of SRT handshake that is generally used for simpler, non-IT-managed networks. If Premiere Pro is in Rendezvous Mode, the viewing client must also be in the same mode.

Typically, no intervention is needed from your IT administrator to traverse a firewall in Rendezvous Mode. The firewalls automatically route the UDP data to the correct endpoint. Both endpoints send handshake packets or data on the same port.

How to save a group of SRT settings?

Add the ability to save a group of SRT settings for easy recall.

Modes

• Listener Mode: Set Premiere into Listener Mode and use it in connection with Caller Mode for a viewing client. In Listener Mode, the viewing client will initiate the SRT handshake.
• Caller Mode: Sets Premiere into Caller Mode and use it in connection with Listener Mode for a viewing client. In Caller Mode, Premiere Pro will initiate the SRT handshake.
• Rendezvous Mode: Set Premiere Pro into Rendezvous Mode and use it in connection with other viewing clients in the same mode. In Rendezvous Mode either premiere Pro or the viewing client can initiate the SRT handshake.

Stream ID

An ID can be added to identify an SRT over the network. Only available in Caller Mode.

Address

The IP address that will be used for the SRT handshake connection. In the Caller Mode, it will be the IP address of the machine or computer hosting the viewing client. In Rendezvous Mode, it will be the IP address of the other machine or computer also in Rendezvous Mode with the viewing client.

Port

The port used for the SRT handshake and stream.

Passphrase

The passphrase is used to validate an encrypted SRT stream. It must be between 10 and 79 characters long.

Latency

Additional latency added to the stream is measured in milliseconds. Increasing this value will potentially allow more packets to be resent in the SRT stream, making the stream more robust. This also will add more delay to the stream. If both endpoints have differing values for the latency setting, the higher of the two values will be chosen. The latency setting is from 0 ms (none) to 1000 ms (1 second).

Quality Settings

Quality settings of the SRT stream can be used to manage the network bandwidth of the stream. Set to a lower quality setting to use less bandwidth. Higher settings will have higher quality at a higher bandwidth cost.

Streaming Indicator

When a valid SRT connection is made, and a stream is sent from Premiere Pro, the Streaming Indicator will be seen in either the Program Monitor or the Source Monitor. This is a quick visual indicator that the SRT streams are being sent to a viewing client.

Related resources

• SRT deployment guide
• SRT alliance deployment guide
• Editing workflows for feature films

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