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[webrtc-pc] Receive a track multiple times

From: Miguel París via GitHub <sysbot+gh@w3.org>
Date: Tue, 29 Nov 2016 17:19:27 +0000
To: public-webrtc@w3.org
Message-ID: <issues.opened-192344906-1480439963-sysbot+gh@w3.org>
mparis has just created a new issue for 
https://github.com/w3c/webrtc-pc:

== Receive a track multiple times ==
Hello,
while implementing we are dealing with the case of receiving the same 
track twice.
There are typically 2 cases:

### Receive a track previously removed
As explained in [1]:
> When the other peer stops sending a track in this manner, an ended 
event is fired at the MediaStreamTrack object.

The problem is that when the track is ended, it cannot be reused again
 [2].
So how should we manage the case of receiving again a track that has 
been set as ended?

### Receive the same track multiple times
The same track can be sent multiple times using addTransceiver[3].
How the receiver side should deal with this case?
A priori, we could have different MediaStreamTrack objects with the 
same ID and performing multiple onTrack events, but the ID should be 
unique, so this is not a proper solution.

## Solution proposal
As solution, I think that we must not allow sending a track more than 
once through addTransceiver in the same way addTrack is doing [4]:

>If an RTCRtpSender for track already exists in senders, throw an 
InvalidAccessError exception and abort these steps. 

And in the case that a receiver get this situation, it should reject 
the m-line associated.
In the case that the user wants send the same media multiple times, 
she should clone the track to generate a new ID.

What do you think about that?

Best!!

## Refs
[1] https://www.w3.org/TR/webrtc/#dom-rtcpeerconnection-addtransceiver
[2] 
https://www.w3.org/TR/mediacapture-streams/#idl-def-MediaStreamTrackState.ended
[3] https://www.w3.org/TR/webrtc/#dom-rtcpeerconnection-addtransceiver
[4] https://www.w3.org/TR/webrtc/#dom-rtcpeerconnection-addtrack

Please view or discuss this issue at 
https://github.com/w3c/webrtc-pc/issues/954 using your GitHub account
Received on Tuesday, 29 November 2016 17:19:36 UTC

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