The default configuration in TSBPD mode is

• SRTO_MSS = 1500;
• SRTO_PAYLOADSIZE = 1316.

Trying to send a payload exceeding SRTO_PAYLOADSIZE leads to an error returned from srt_sendmsg2(..).
In the live configuration, it is expected that a message must fit into a single SRT data packet.

If SRTO_MSS < SRTO_PAYLOADSIZE, a message will be split into two packets.
For e.g. setting SRTO_MSS = 1300 and sending 1316 bytes long messages would produce two packets per message.

SRT v1.5.1 and prior.