Re: [sipcore] About Join and Replaces Headers: //Replaces header's extension

["Worley, Dale R (Dale)" <[e-mail]>]

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From: [e-mail] [[e-mail]]

X -------------------- Y
      voice/video

//Y send voice/video session to X. As Y does not know X support HD video, so he send the call from a normal UE.

moving to (2):

  X -------------------- Y
  |       voice
  |
  +--------------------- Z
        HD video

//Then, X tell Y that his UE support HD video and want to establish the HD video stream. Please note that, X tell Y by voice, while not by any signalling.

//Then, Y use a new equipment(Z) to transfer the video stream from the orignal session. The voice stream is still between X and Y.
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(BTW, you are using the same symbols for the *users* and the *UAs* here, and that creates confusion.)

If user Y (using UA Z) sends an INVITE-with-Replaces to X, then the original dialog (between UAs X and Y) *must* be terminated by X when it accepts the INVITE-with-Replaces.

What UA Z should do is send an INVITE-with-Join to X (offering only video), and then UA Y should do a re-INVITE to remove its video stream from its dialog with X (leaving the audio stream).  At that point, X is "mixing" two dialogs, but each media stream (audio and video) is used by only one leg of the conference, so X doesn't need to do any actual mixing processing.

Dale