[rtcweb] Add, remove, add, remove, add, remove a media stream (lines in SDP)

[Iñaki Baz Castillo <[e-mail]>]

Hi, a stream in an SDP cannot be removed but just "disabled" (by
setting its port to 0). In the same media session a participant could
add a video stream and "disable" it later multiple times.

Let's assume a media session initiated with just an audio stream:

1) A participant adds a video stream and the remote accepts it. This
involves a new media section in the SDP.
2) Later the same participant removes the video stream which means
setting its port to 0 in the SDP.
3) Later he adds video again.
4) ...and so on.

AFAIK there are two choices for step 2 and 3:

a) Releasing video resources and the UDP socket so when video is
enabled again a new line should be added to the SDP and new resources
(ICE, UDP socket) required.

b) Not releasing all the resources (keep the UDP socket but stop
sending/receiving data on it), and re-enabling it when video is added
again, so the same SDP line would be reused by setting its port to the
previous value.


Choice a) means more and more lines in the SDP for each video
activation. Option b) means not releasing resources after disabling a
media stream.

If I'm not wrong in the above text, which would be the WebRTC approach
for this topic?

Thanks a lot.

-- 
Iñaki Baz Castillo
<[e-mail]>