Re: UserMediaSettings

I probably would have supported this API had it been proposed a year ago but at  this point I don’t see any advantage of it and I’m not seeing much consensus to change to it.  


On Feb 21, 2014, at 5:13 AM, Jan-Ivar Bruaroey <jib@mozilla.com> wrote:

> (Hopefully fixes messed-up indentation)
> 
> Constraints went general at every turn. What if we went the other way?
> 
> Roc's MediaRecorder proposal http://lists.w3.org/Archives/Public/public-media-capture/2014Feb/0001.html was dismissed for not being compatible with constraints in gUM, so it seems there's no way around addressing gUM.
> 
> Here's how to solve gUM with dictionaries, while keeping functional parity.
> 
> The goal is to learn from constraints yet rid the spec of them entirely, as nothing less will simplify.
> 
> dictionary UserMediaSettings {
>    boolean video;
>    boolean audio;
>    DOMString peerIdentity;
>    long width;
>    long height;
>    double aspectRatio;
>    double frameRate;
>    VideoFacingModeEnum facingMode;
>    double volume;
>    unsigned long sampleRate;
>    unsigned long sampleSize;
>    boolean echoCancelation;
> 
>    // Dictionary may be extended through gUM-specific IANA registry.
> };
> 
> dictionary Request {
> {
>    DOMString require; // explained below
>    DOMString prefer;  // explained below
> };
> 
> dictionary UserMediaSettingsRequest : Request {
> {
>    boolean video;
>    boolean audio;
>    DOMString peerIdentity;
>    (unsigned long or UnsignedLongRequest) width;
>    (unsigned long or UnsignedLongRequest) height;
>    (double or DoubleRequest) aspectRatio;
>    (double or DoubleRequest) frameRate;
>    (VideoFacingModeEnum or sequence<VideoFacingModeEnum>) facingMode;
>    (double or DoubleRequest) volume;
>    (unsigned long or UnsignedLongRequest) sampleRate;
>    (unsigned long or UnsignedLongRequest) sampleSize;
>    boolean echoCancelation;
> 
>    // Dictionary may be extended through gUM-specific IANA registry.
> };
> 
> dictionary UnsignedLongRequest {
>    unsigned long min;
>    unsigned long max;
>    unsigned long ideal;
> };
> 
> Clients may list the names of keys they require. Example:
> 
>  var request =
>  {
>    require: "width, height",
>    width: { min: 640, ideal: 1280 },
>    height: { min: 480, ideal: 768 },
>    aspectRatio: 16/9,
>    frameRate: 60,
>    facingMode: "user",
>  };
>  navigator.getUserMedia(request, success, failure);
> 
> If they do, getUserMedia will fail if required keys are either missing, unknown or unsatisfied.
> 
> There is no order by default, instead sources are ranked by how many settings they satisfy, with the UA breaking a tie for the default choice (which end-users may ultimately override).
> 
> Clients who prefer an order may do this:
> 
>  var request =
>  {
>    require: "width, height",
>    prefer: "aspectRatio",
>    width: { min: 640, ideal: 1280 },
>    height: { min: 480, ideal: 768 },
>    aspectRatio: 16/9,
>    frameRate: 60,
>    facingMode: "user",
>  };
>  navigator.getUserMedia(request, success, failure);
> 
> which will pick a 16:9 environment-facing 75Hz camera over a user-facing 60hz 4:3 camera, without requiring 16:9.
> 
> getUserMedia will not fail if preferred keys are missing, unknown or unsatisfied.
> 
> MediaStreamTrack re-absorbs the affected functionality:
> 
> interface MediaStreamTrack : EventTarget {
> 
>    UserMediaSettingsRequest getInherentCapabilities ();
>    UserMediaSettings        snapshotCurrentSettings ();
>    void                     applySettings (UserMediaSettingsRequest settings,
>                                            VoidFunction successCallback,
> ConstraintErrorCallback errorCallback);
>                attribute EventHandler onconflict;
> 
>    readonly    attribute DOMString             kind;
>    readonly    attribute DOMString             id;
>    readonly    attribute DOMString             label;
>                attribute boolean enabled;
>    readonly    attribute boolean               muted;
>                attribute EventHandler onmute;
>                attribute EventHandler onunmute;
>    readonly    attribute boolean _readonly;
>    readonly    attribute boolean remote;
>    readonly    attribute MediaStreamTrackState readyState;
>                attribute EventHandler onstarted;
>                attribute EventHandler onended;
>    MediaStreamTrack clone ();
>    void             stop ();
> };
> 
> More than just renaming, there is no universal constraint concept, no Constrainable interface, no object-based constraint object, and no co-mingled domain-spanning data definitions outside of WebIDL.
> 
> Things are well defined in context using standard WebIDL.
> 
> MediaRecorder may borrow what little it needs or invent its own API.
> 
> .: Jan-Ivar :.
> 
> 
>

Received on Friday, 21 February 2014 09:39:05 UTC