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ACCEPTED: Media streams, media stream tracks and channels

From: Harald Alvestrand <harald@alvestrand.no>
Date: Fri, 09 Dec 2011 13:02:19 +0100
Message-ID: <4EE1F8CB.2000305@alvestrand.no>
To: "public-webrtc@w3.org" <public-webrtc@w3.org>
Resurrecting this thread from last month:

On 11/08/2011 01:15 AM, Harald Alvestrand wrote:
> Discharging a task taken on at the TPAC meeting, some possible words 
> on what a media stream, a media stream track or a channel is....
>
> This is based on the introduction section in section 3.1 of the 
> current API editors' draft.
>
> The|MediaStream 
> <http://dev.w3.org/2011/webrtc/editor/webrtc.html#mediastream>|interface 
> is used to represent streams of media data, typically (but not 
> necessarily) of audio and/or video content, e.g. from a local camera 
> or a remote site. The data from a|MediaStream 
> <http://dev.w3.org/2011/webrtc/editor/webrtc.html#mediastream>|object 
> does not necessarily have a canonical binary form; for example, it 
> could just be "the video currently coming from the user's video 
> camera". This allows user agents to manipulate media streams in 
> whatever fashion is most suitable on the user's platform.
>
> Each|MediaStream 
> <http://dev.w3.org/2011/webrtc/editor/webrtc.html#mediastream>|object 
> can represent zero or more tracks, in particular audio and video 
> tracks. Tracks can contain multiple channels of parallel data; for 
> example a single audio track could have nine channels of audio data to 
> represent a 7.2 surround sound audio track.
>
> <new text below>
>
> All tracks in a MediaStream are presumed to be synchronized at some 
> level. Different MediaStreams may or may not be synchronized.
>
> Each track in a|MediaStream 
> <http://dev.w3.org/2011/webrtc/editor/webrtc.html#mediastream>|object 
> has a corresponding|MediaStreamTrack 
> <http://dev.w3.org/2011/webrtc/editor/webrtc.html#mediastreamtrack>|object.
>
> A MediaStreamTrack represents content comprising one or more channels, 
> where the channels have a defined well known  relationship to each 
> other (such as a stereo or 5.1 audio signal), and may be encoded 
> together for transmission as, for instance, an RTP payload type. One 
> MediaStreamTrack sent to another peer MUST appear as one and only one 
> MediaStreamTrack to the recipient.
>
> A channel is the smallest unit considered in this API specification.
>
> <end new text>
>

I made a couple of text changes to make it clearer following the 
discussion (represented by -> in, added text saying that one track 
@sender = one track @recipient).

At this stage, I'd like to ask our editors to incorporate this text. It 
seems "right enough".

                 Harald
Received on Friday, 9 December 2011 12:03:02 UTC

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