IS-04 doesn't distinguish between ST 2110-21 Type A and Type W Receivers

[garethsb]

VSF TR-08 defines two Timing Recovery Modes for Receivers: SYNC and ASYNC. These are based on ST 2110-21 Type W and Type A Receivers.

Using BCP-004-01 Receiver Capabilities, Receivers can indicate which ST 2110-21 Sender Types they support, but both Type W and Type A Receivers would indicate exactly the same thing:

"st2110_21_sender_type": {
  "enum": [
    "2110TPN",
    "2110TPNL",
    "2110TPW"
  ]
}

The difference between Type W and Type A Receivers is whether they can accept streams from Senders with a different timing source (or different TROFF values?).

The timing source of a Sender is indicated via the a=ts-refclk: attribute line in the SDP data, and in the IS-04 Node clocks entry indicated by the Sender clock_name.

However, the timing source associated with a Receiver is not indicated in IS-04.

Do we need to (a) add a Receiver attribute clock_name, and (b) add a Boolean Receiver attribute indicating asynchronous support?

[peterbrightwell]

Architecture Review Group review: place on backlog