W3C home > Mailing lists > Public > public-media-capture@w3.org > March 2013

Re: How do we enable/select tracks for playout?

From: Martin Thomson <martin.thomson@gmail.com>
Date: Wed, 20 Mar 2013 11:32:46 -0700
Message-ID: <CABkgnnWb1vFi5tuxAVQ6zWDPub8+6XufKmtoeJ8_nLPCcwzYfg@mail.gmail.com>
To: Travis Leithead <travis.leithead@microsoft.com>
Cc: Adam Bergkvist <adam.bergkvist@ericsson.com>, Jim Barnett <Jim.Barnett@genesyslab.com>, Harald Alvestrand <harald@alvestrand.no>, "public-media-capture@w3.org" <public-media-capture@w3.org>
On 20 March 2013 10:32, Travis Leithead <travis.leithead@microsoft.com> wrote:
>> > I think this makes sense in a way. The enable/disable is just a switch
>> > on the tracks that turns the "output" on or off, and doesn't
>> > necessarily have anything to do with how the sink chooses which tracks to
>> > render.
>
> This is how I've always assumed that it worked....

That's perfectly fine, though I'm not convinced that it's really
necessary, it seems like we have this flag only because this flag was
there.  Inertia is a dangerous force.  We can get back to that.

>> This alternative is exactly what I want, though "activeVideoTrack" and
>> "activeAudioTrack" might be more appropriate names.  You could
>> automatically populate these attributes with the first track of each type that
>> is added so that simple uses are supported.
>>
>> One other advantage is that "muting" can then be achieved by setting this
>> mutable property to null/undefined.  If something isn't active, then it isn't
>> rendered.
>
> So as I understand, setting enabled=false does not cause the 'muted' event to fire, right? But you're proposing that setting activeVideo/AudioTrack to null/undefined would cause this event to fire? Is 'muted' (the event name) still a good name for the "absence of media content" state?

Let's just say that the muted state is the logical AND of a physical
mute button and a logical mute button (presumably the enabled
attribute).  The muted event might fire as a result of either, though
this might depend on whether it is possible to detect changes in the
physical button state.

I'm suggesting that - for sinks that only consume the active track -
we have a way to select the active track.  Selecting nothing isn't
quite muting, but it can appear as though it was.
Received on Wednesday, 20 March 2013 18:33:13 UTC

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