method to get which stream was opened

[dvdsk]

For context see: #662 (comment)

maybe a method on OutputStream would work?

[PetrGlad]

There are 3 options:

1. Return as another value when opening the stream ((info, stream-handle)). This would force users to ignore info part, and it again looks like the older version of the API...
2. Just write this info to logs (through tracing).
3. Keep the information in the stream handle, and let users to read it.

Yes, the latter seems to give users most choices, and does not interfere if they do not care.
I think we'll need to show not only actual device name, but also the actual stream format. So there is possibility for sources to adjust if they can (#646).