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Re: How to know if a given track or media stream is being transmitted

From: Iñaki Baz Castillo <ibc@aliax.net>
Date: Fri, 14 Jun 2013 21:07:06 +0200
Message-ID: <CALiegfmZMEeR=d+AUR5VGEMKVQeEg7Va0dWJra=k2jQrBDEaMw@mail.gmail.com>
To: José Luis Millán <jmillan@aliax.net>
Cc: "public-webrtc@w3.org" <public-webrtc@w3.org>
This is the typicall scenario in which a peer wants to add video to a
only-audio session, and also wants to know whether it is in fact
sending its local video to the peer, and whether the remote peer is
receiving it or not.

For example, all the people expect that, when using Skype, if we see
our own local video that means that we are sending it to the remote
peer. Otherwise the application hides our local video and switches off
the webcam.

Due to SDP extra-flexibility there are multiple ways to indicate that
video is not being received:

- The peer answers an SDP with m=video line with port 0.
- The peer answers an SDP with m=video line active but a=recvonly.
- May be another way due to the addition of "track" concept.

Is there a reliable API for detecting all those cases?

Thanks a lot.

2013/6/14 José Luis Millán <jmillan@aliax.net>:
> Hi,
>
> I wonder if the following scenarios are considered in the WebRTC API.
>
> Alice and Bob have a peerConnection each. Both have a mediaStream loaded in
> their peerConnection. The mediaStream in Alice's peerConnection has one
> audio track and zero video tracks, Bob's has one audio and one video track.
>
> Alice sends a SDP offer to Bob. She wants to establish an audio media
> session. Bob receives the offer and answers Alice. Both SDPs have an audio
> only media description.
>
> After a while Bob decides to share his video with Alice. He looks at his
> peerConnection and he notices he actually has a video track, but he doesn't
> know whether he is already sending that video to Alice or not.
>
> How does Bob know if he is sending his video to Alice by looking at his
> peerConnection?
>
> Another scenario is the one where Carol offers Alice a SDP offer containing
> audio and video media description and Alice only accepts the audio, she is
> not willing to receive any video from Carol.
>
> How does Carol know she is not sharing her video?
>
> Same for entire mediaStreams in a peerConnection.
>
> I can't figure out how to achieve it. Have this been considered?
>
> Regards,
>
> --
> José Luis Millán



-- 
Iñaki Baz Castillo
<ibc@aliax.net>
Received on Friday, 14 June 2013 19:07:54 UTC

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