Expected Behaviour: IS-04 video source/flow initial properties when format is as yet unknown

[matthewdicken]

When a device appears on the network and wants to register video sources/flows/senders, those resources are required to have valid properties e.g: bit_depth, height, width, grain_rate... A device that is configured to follow the input video format could be brought online without a valid input signal connected. It would not know the required values until such a time when a valid input signal is detected, but the NMOS schema requires them.

What is the expected behaviour in this scenario?

[garethsb]

Option 1. Don't create the Flow (and maybe even the Source) before the values are known.
Option 2. Create the Flow and put in default values until the actual values are known.
Option 2a. Create the Flow and put in sentinel values (0 bits, 0 × 0, 0/1 Hz, etc.) until they are known.

All have pros and cons. Which combination of pros and cons would you prefer and why?

[Mantls]

Dynamic Resource Creation/Deletion is the bane of all (well most) control systems.

Create the flow and use default values (something like 0 wherever possible), that would be my advice. It's not pretty but the alternative causes more problems in my experience.

[garethsb]

Control systems like this are dinosaurs. Dynamic systems - with strong identity across service restarts, etc. - are here to stay.

Corollary to option 1 - you can have the Sender always present, but leave it with "flow_id": null until the Flow is available.