Supplementary Information

GRIDSHOT® provides SRT output connections from its playout service. Secure Reliable Protocol (SRT) is a point to point connection between a server and client. In order to receive the channel, a SRT socket connection must be established (1) and data transferred (2).

Step 1: Establish SRT connection

There are two roles within SRT when a connection is established between two parties.

  • Listener:     Server waiting for incoming connections
  • Caller:         Initiates connection to the listener

1.1 GRIDSHOT® takes on the Listener role and the customer takes on the Caller role. We authenticate the customer with IP whitelisting and an optional hash in the SRT streamid header.

1.2 GRIDSHOT® provides the SRT endpoint listener IP address and port, and stream decryption passphrase to the customer, which it can use to initiate the SRT connection request to our playout server. This will also provide the customer the opportunity to whitelist our IP address in their firewall if applicable. Incoming and outgoing UDP packets to our IP address should be allowed.

1.3 The customer provides their static IP address / range (class C) used to initiate the SRT connection, which GRIDSHOT® can whitelist as part of the authentication process.

1.4 The customer shall make sure that their SRT client software is at least version 1.4.1 or we may reject the connection attempt to ensure proper compatibility between the Listener and Caller.

Step 2: Receiving TV channel stream through SRT

Once the customer has been successfully authenticated by GRIDSHOT®, a connection is established. At this phase there are two roles within SRT.

  • Sender:        Server actively sending SRT packets
  • Receiver:     Client application receiving the SRT packets from the Sender

2.1 GRIDSHOT® takes on the Sender role and the customer takes on the Receiver role.

2.2 SRT packet rate control is managed by GRIDSHOT®.

2.3 While SRT is built to be as reliable as possible over unreliable networks. Many factors like latency, jitter and bandwidth which are outside of anyone’s control may degrade the signal quality.

2.4 As part of improving the SRT connection stability, GRIDSHOT® may be required to conduct latency testing with the customer.

2.5 If the customer enters the wrong decryption key provided by GRIDSHOT®, it won’t receive an SRT stream and the connection will be terminated.


Our SRT implementation are tested and verified by engineers from multiple companies and products:

  • Appendix 1: FFmpeg (minimal required version 4.0)


FFmpeg version 4.0 onwards has support for the SRT protocol. This implementation is based on the same library as our playout solution. The following command shows how to set up a connection with SRT.

ffmpeg -i 'srt://[PLAYOUT IP]:[PORT]?mode=caller&passphrase=[PASSPHRASE]&transtype=live'

Contact and support

Should there be any technical issues or questions regarding the application of SRT setup please contact theFrontDoor at

Please note that SRT delivery travels over the open internet and is therefore 100% dependent on the availability of the open internet. As the open internet is outside our control no guarantees on service levels can be given. For a fully redundant GRIDSHOT® playout on location GRIDSHOT® guarantees a 99,99 % service level.