Mqtt statestream payload format

I am subscribing from a mqtt client on a different machine to a mqtt server (broker) running as an integration in HA. I a using mqtt statestream within HA. My client connects, and receives HA events as a json formatted string. All text within the json string is plain text, except for the Payload name/value pair. This appears to be in a different format, as you can see in the example json below:


The Payload comes across as: b2Zm
Does anyone know what formatting is used for Payload?

Never mind, it is base 64 encoded.