Re: Media Capture and Streams Last Call review

Hello Stefan,


Thank you for your recent solicitation of feedback to on the Media Capture
and Streams API, which I passed to the Web Audio Working Group.


The Web Audio WG so far has identified one key item that we would like to
see addressed. The MediaDeviceInfo result from enumerateDevices() (
http://www.w3.org/TR/2015/WD-mediacapture-streams-20150414/#idl-def-MediaDeviceInfo)
lacks information that is typically available in the underlying OS
implementations that we think would be very helpful for implementations:



·         Channel count and configuration (Mono, Stereo, 5.1, 7.1, etc…)

·         Physical Output (Headphone, Speaker, HDMI, …)

·         Latency (this matters a lot for gaming -- it will be very low for
on-board hardware, perhaps quite high for wireless audio bridging like
Apple TV)

·         Output capabilities (bitstream passthrough vs PCM – relevant in
digital media adapter cases (Chromecast, etc))


It is perhaps sufficient from a user interface point of view to have a
string to display, but for a program to be able to either adapt to the user
selection or to guide and default the user selection, the above are pretty
important characteristics, at least in some use cases. Many if not most of
the host OSes that user agents run on expose these sorts of output device
characteristics.


Aside from the difficulty with enumerating devices, there is also perhaps a
need to make it possible for applications to query the set of available
devices with respect to the above charateristics. MediaTrackConstraints and
MediaTrackSettings do not currently  include constraint attributes that map
to items in the above list. And even if they do, arriving at a
practical goodness-of-fit
metric that can be generalized across a spectrum of audio apps may be
difficult.



The same concerns apply to the set of input devices.



Please let us know if this issue makes sense to the group and can be
addressed within the timeframe of the coming run-up to a Last Call WD. We'd
be happy to arrange some sort of inter-WG call to try to make progress on
this together.


Thank you!


Best regards,


Joe Berkovitz

co-chair Web Audio WG


*Noteflight LLC*
Boston, Mass.
phone: +1 978 314 6271
www.noteflight.com
"Your music, everywhere"

On Wed, Apr 15, 2015 at 1:31 AM, Stefan Håkansson LK <
stefan.lk.hakansson@ericsson.com> wrote:

> The WebRTC and Device APIs Working Groups request feedback on the Last
> Call Working Draft of Media Capture and Streams, a JavaScript API that
> enables access to cameras and microphones from Web browsers as well as
> control of the use of the data generated (e.g. rendering what a camera
> captures in a html video element):
> http://www.w3.org/TR/2015/WD-mediacapture-streams-20150414/
>
> The groups have identified the following other W3C Working Groups as
> likely sources of feedback:
>
> - HTML Working Group, especially the HTML Media Task Force, as our API
> extends the HTMLMediaElement interface and defines a new type of media
> input via MediaStream
>
> - WebApps Working Group, especially on the overall usage of Web IDL and
> the definition of error handling
> Audio Working Group, as the Web Audio API builds upon the MediaStream
> interface
>
> - WAI Protocol and Formats Working Group, especially on the impact of
> the user consent dialog and the applicability of the indicators of
> device usage in assistive tools
>
> - Web and TV Interest Group, as the manipulation of media input can be
> relevant to some of their use cases (e.g. glass to glass)
>
> - Web App Security Working Group, especially on our links between
> secured origins and persistent permissions, and our current policy with
> regard to handling access to this "powerful feature"
>
> - Web Security Interest Group, especially on our security considerations
> Privacy Interest Group, as access to camera and microphone has strong
> privacy implications
>
> - Technical Architecture Group, for an overall review of the API,
> especially the introduction of the concept of a IANA registry-based
> constraints system, the use of promises, and our handling of persistent
> permissions
>
> We naturally also welcome feedback from any other reviewers.
>
> The end of last call review for this specification is set to May 15
> 2015; should that deadline prove difficult to meet, please get in touch
> so that we can determine a new deadline for your group.
>
> As indicated in the document, comments should be sent to the
> public-media-capture@w3.org mailing list.
>
> Thanks,
>
> Frederick Hirsch, Device APIs Working Group Chair,
> Harald Alvestrand and Stefan Hakansson, WebRTC Working Group Chairs and
> Media Capture Task Force Chairs
>



-- 
.            .       .    .  . ...Joe

*Joe Berkovitz*
President

*Noteflight LLC*
Boston, Mass.
phone: +1 978 314 6271
www.noteflight.com
"Your music, everywhere"