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Re: Proposal for API for Data

From: Harald Alvestrand <harald@alvestrand.no>
Date: Thu, 15 Mar 2012 17:13:50 +0100
Message-ID: <4F62153E.4040709@alvestrand.no>
To: Cullen Jennings <fluffy@cisco.com>
CC: public-webrtc@w3.org
On 03/15/2012 02:34 PM, Cullen Jennings wrote:
> I had a proposal for the Data API for awhile and have circulated it privately to some folks but I had not sent it to the list because I wanted to keep the focus on the PeerConnection / JSEP stuff for awhile. However, I think I probably need to send this out. I think at the high level there is general agreement we need to be abel to send and receive data much like web sockets does, we need to be abel to create and destroy channels, and we need to be able to mark a channel as reliable or non reliable delivery. The API I'm proposing to do this is very simple.
>
> Interface DataMediaStreamTrack : MediaStreamTrack
> {
>       attribute boolean reliable;
> }
> DataMediaStreamTrack implements WebSocket;
>
>
> This ends up getting the function to send and receive data as well as report errors fromWebSocket. Any library that takes a WebSocket can take a DataMediaStream. It unifies creation of a new stream to be the same as MediaStreams. So in the same way that a new Video track was created, you can add a data track or remove one. It is labeled in same way as the the other tracks and so on. It seems like i works well for data sources that are from the JS app and it also can be used with data sources, such as a sensor or game controller, that may be more controlled by the browser in the same way a microphone or camera is more controlled form the browser. That will allow for better real time performance of devices that produce a data stream instead of an media stream.
>
> I'd like to discuss on one of the call the pros / cons of such an interface but right now I am heads down on the JSEP changes.
At one point I argued something similar....

the biggest worry I have with this approach is that it inherits a lot of 
stuff that doesn't seem to make sense, for instance:

- "mute" functions from the MediaStreamTrack: What does it mean to 
"mute" a data channel?
- track manipulations: what does it mean to add a DataMediaStreamTrack 
to two MediaStreams?
Perhaps nothing, since there still can be only one handler (or handler 
list) for the onmessage() function anyway?
- "url" and "extensions" attributes from the WebSocket API: Do they have 
meaning? Are "extensions" names from the same namespace as for WebSockets?

But I agree that getting the JSEP changes done is more important...

           Harald
Received on Thursday, 15 March 2012 16:14:17 GMT

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