> ## Documentation Index
> Fetch the complete documentation index at: https://docs.up.telestream.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Expected properties

> What a source's stream is expected to look like.

The `expected_properties` of a source tell the engine what to expect from the stream before it arrives, so it can be received correctly and a stream that turns out different can be reported.


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