Re: Proposal for output device selection

Thanks Chris for the summary, this looks overall right to me. The semantics
expressed in #2 are also useful for indicating relative priority, i.e. that
an incoming voice call should duck audio from a video playback.

We are already dealing with the privacy implications of #3 for the input
scenarios, so adding output isn't creating any new problems.


On Fri, Aug 16, 2013 at 10:09 AM, Chris Wilson <cwilso@google.com> wrote:

> I think there are multiple independent vectors for audio output selection:
>
>    1. Channel/speaker model selection: "I want this to go to the center
>    speaker/this is a 5.1 sound clip".  The Web Audio spec defines this for
>    mono/stereo/4-ch/5-ch layouts:
>    https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/specification.html#ChannelLayouts
>    .
>    2. Semantic role of audio - this is the "background music" vs "game
>    audio" vs "voice call" definition - the "logical channel".  For example,
>    I'd like to have my phone route voice calls to my BT headset, but music
>    playback to the BT car connection, and game sound to the device speakers
>    (so my daughter, playing games on my phone in the back seat, doesn't
>    disrupt my call or stop the music).  Y'know, hypothetically.  :)
>    3. Big ol' pile of channels - the music production case.  I have a
>    minimal version of this on my desk at work - I want to be able to change
>    routings because most of the time I've got a headset on but occasionally
>    want to switch to a different output that's speaker-based to demo something.
>
> I think #1 is solved for Web Audio, and likely (haven't tested) works for
> <audio> (it should, anyway).  #2 is the focus of the mobile-necessary (but
> not inapplicable to desktop!) Mozilla proposal; it's also related to the
> single "default audio device" model in Web Audio today.  #3 is a different
> beast to me, and might (as Rob suggests) have privacy implications to
> expose all devices; however, it's still a requirement for even
> middling-complexity audio scenarios.
>
> Most desktops - for input and output devices, both audio and video (for
> input) define a single "default device", but not a semantic collection of
> devices.  I think semantic roles make sense for #2, but not for #3.
>
>
>
> On Fri, Aug 16, 2013 at 9:49 AM, Justin Uberti <juberti@google.com> wrote:
>
>> Yes, I forgot to spell out how the application would route its output to
>> left/center/right audio devices.
>>
>> Regardless, if this approach is applicable for input devices, I don't see
>> why we would want a different model for output.
>>
>> On Thu, Aug 15, 2013 at 6:58 PM, Robert O'Callahan <robert@ocallahan.org>wrote:
>>
>>> On Fri, Aug 16, 2013 at 11:14 AM, Justin Uberti <juberti@google.com>wrote:
>>>
>>>> Different applications may want to have different UIs to control these
>>>> settings. One application may just want to control a single camera and
>>>> audio device. Another application may want to have multiple cameras all
>>>> used in concert, and allow the left/right/center camera/mic devices to be
>>>> individually selected.
>>>>
>>>
>>> You seem to be talking about input devices. I thought we were talking
>>> about output.
>>>
>>> Rob
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>>
>>
>