[Telepathy] Just what is stream directionality?

[Simon McVittie]

On Fri, 13 Mar 2009 at 22:11:35 +0000, Sjoerd Simons wrote:
> On Fri, Mar 13, 2009 at 05:51:54PM +0000, Simon McVittie wrote:
> > How Gabble implements it
> > ========================
> > ...
> > If a call to RequestStreamDirection enables receiving, we tell the remote
> > contact to send us media, and blindly assume that they will do so (the
> > StreamDirectionChanged signal immediately indicates that we expect to receive)
> 
> You never have any guarantee that the remote side will actually send though.
> You can argue whether it makes sense to request the remote side to start
> sending immediately  (apart from when the call is initiating), as it should
> always be something the user on the other side decides not their peer.

Sorry, I couldn't parse that. When you say "you can argue", what are the two
(or more?) points of view that one could argue in favour of?

> If they'll be sending us media, you'll receive media. The senders property in
> jingle as at best informational.

Well, this is StreamedMedia, not MediaSignalling - it's all informational
anyway. AIUI, StreamedMedia is just for telling the UI what status indicators
and controls to display, and having the UI feed control input back to the
channel?

In a sense, distinguishing between pending-remote-send and receiving is futile
anyway, since UIs aren't likely to present them differently (or are they?
answers on a postcard). OTOH, perhaps distinguishing between pending-local-send
and sending is important so the UI knows whether it needs to solicit user
input (a la MSN: "Simon has asked you to enable video. (OK | cancel)"),
although AIUI none of our current UIs do that.

> In case there would be an affirmative message, it would just be for debugging.
> You always have to listen for incoming traffic as their media will probably
> arrive on your side faster then the message through the signalling.. If you get
> the message before the media, you know something might be wrong or maybe you
> just need to wait a little bit... Also know as not very usefull.

Right, so you need to be listening for media whenever the receive state is
either RECEIVE or PENDING_REMOTE_SEND? That's fine. Also, this isn't
MediaSignalling anyway.

    S