Re: [splices] Answering a Call Using Two Separate Devices proposal

[Peter Musgrave <[e-mail]>]

Hi Rifaat,

Overall I think this works. 

1) Use of INVITE from phone to PC to signal addition of video:

The current mechanism (with an new INVITE to the PC from the phone) seems likely to me to cause the call to ring on the PC - and I think having a call that is already in progress ring a second device as a means of signalling the availability of video will not be the ideal user experience (or perhaps when the device sees an INVITE with video and no audio it knows not to alert the user in the usual way?)

One alternative would be:

When the accept on the PC results in the:
    | REFER Refer-To: urn:sip-action:call:answer    
                  |
message from the PC to the phone does it make sense for the PC to subscribe to the dialog-state of the call at this point? (In fact would it hurt to have the coupled devices always subscribed to each other's dialog state?)

Then when a reINVITE with video is offered the PC will receive a notification and it can offer the user a choice to accept the call there - with some pop-up and beep (or whatever). If the user accepts then it could send a REFER to the phone to make it offer video to the PC. (I first thought of using an INVITE with JOIN from PC to phone - but then the video offer comes from the PC and forces the phone to build a video answer based on the PCs offer - which seems a bad idea). 

2) As an aside, how does lipsync on sending and playout get handled in this configuration? 

Regards, 

Peter Musgrave