Edit comment LC-3023 for Web Real-Time Communications Working Group

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Comment LC-3023

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[Free text description]Document as a wholeMedia Capture and Streams Abstract Status of This Document 1. Introduction 2. Conformance 3. Terminology queue a task fires a simple event event handlers event handler event types source Constraints RTCPeerConnection 4. MediaStream API 4.1 Introduction 4.2 MediaStream MediaStream() When the constructor is invoked track set consumer active inactive 4.2.1 Constructors MediaStream 4.2.2 Attributes active of type boolean, readonly id of type DOMString, readonly id onactive of type EventHandler, onaddtrack of type EventHandler, oninactive of type EventHandler, onremovetrack of type EventHandler, 4.2.3 Methods addTrack() clone getAudioTracks() getTrackById() getTracks() getVideoTracks() removeTrack() 4.3 MediaStreamTrack 4.3.1 Life-cycle and Media Flow Life-cycle detached ended Media Flow Muted Enabled/disabled 4.3.2 Tracks and Constraints 4.3.3 Interface Definition 4.3.3.1 Attributes enabled of type boolean, MediaStreamTrack.enabled MediaStreamTrack.id MediaStreamTrack.kind MediaStreamTrack.label MediaStreamTrack.muted onended of type EventHandler, onmute of type EventHandler, onoverconstrained of type EventHandler, onunmute of type EventHandler, readonly readyState remote 4.3.3.2 Methods applyConstraints MediaStreamTrack.clone() getCapabilities getConstraints getSettings stop enum MediaStreamTrackState { "live", "ended" }; 4.3.4 Track Source Types enum SourceTypeEnum { "camera", "microphone" }; 4.3.5 MediaTrackSupportedConstraints 4.3.5.1 Dictionary MediaTrackSupportedConstraints Members aspectRatio of type boolean deviceId of type boolean echoCancellation of type boolean facingMode of type boolean frameRate of type boolean groupId of type boolean height of type boolean sampleRate of type boolean sampleSize of type boolean volume of type boolean width of type boolean 4.3.6 MediaTrackCapabilities 4.3.6.1 Dictionary MediaTrackCapabilities Members aspectRatio of type (double or DoubleRange) deviceId of type DOMString echoCancellation of type sequence<boolean> facingMode of type DOMString frameRate of type (double or DoubleRange) groupId of type DOMString height of type (long or LongRange) sampleRate of type (long or LongRange) sampleSize of type (long or LongRange) volume of type (double or DoubleRange) width of type (long or LongRange) 4.3.7 MediaTrackConstraints 4.3.7.1 Dictionary MediaTrackConstraints Members advanced of type sequence<MediaTrackConstraintSet> 4.3.7.2 Dictionary MediaTrackConstraintSet Members aspectRatio of type ConstrainDouble deviceId of type ConstrainDOMString echoCancellation of type ConstrainBoolean facingMode of type ConstrainDOMString frameRate of type ConstrainDouble groupId of type ConstrainDOMString height of type ConstrainLong sampleRate of type ConstrainLong sampleSize of type ConstrainLong volume of type ConstrainDouble width of type ConstrainLong 4.3.8 MediaTrackSettings 4.3.8.1 Dictionary MediaTrackSettings Members aspectRatio of type double deviceId of type DOMString echoCancellation of type boolean facingMode of type DOMString frameRate of type double groupId of type DOMString height of type long sampleRate of type long sampleSize of type long volume of type double width of type long 4.4 MediaStreamTrackEvent 4.4.1 Constructors MediaStreamTrackEvent 4.4.2 Attributes track 4.4.3 Dictionary MediaStreamTrackEventInit Members 5. The model: sources, sinks, constraints, and settings 6. MediaStreams as Media Elements 6.1 Direct Assignment to Media Elements 6.1.1 Attributes srcObject of type MediaStream, , nullable 6.2 Loading and Playing a MediaStream in a Media Element 6.3 Media Element Attributes when Playing a MediaStream 7. Error Handling 7.1 MediaStreamError All errors defined in this specificati... 7.1 MediaStreamError 7.1.1 Attributes constraintName of type DOMString, readonly , nullable message of type DOMString, readonly , nullable name of type DOMString, readonly 7.1.2 Constructors MediaStreamErrorEvent 7.1.3 Attributes 7.1.4 Dictionary MediaStreamErrorEventInit Members 7.2 Error names NotSupportedError PermissionDeniedError ConstraintNotSatisfiedError OverconstrainedError NotFoundError AbortError SourceUnavailableError 8. Event summary active inactive addtrack removetrack mute unmute overconstrained ended devicechange 9. Enumerating Local Media Devices 9.1 NavigatorUserMedia 9.1.1 Attributes mediaDevices of type MediaDevices, readonly 9.2 MediaDevices 9.2.1 Attributes ondevicechange of type EventHandler, 9.2.2 Methods enumerateDevices() 9.2.3 Access control model 9.3 Device Info 9.3.1 Attributes deviceId of type DOMString, readonly groupId of type DOMString, readonly kind of type MediaDeviceKind, readonly label of type DOMString, readonly enum MediaDeviceKind { "audioinput", "audiooutput",... videoinput 10. Obtaining local multimedia content 10.1 NavigatorUserMedia Interface Extensions Note The defi... 10.1 NavigatorUserMedia Interface Extensions Note partial interface NavigatorUserMedia { void getUserMedia... 10.1.1 Methods getUserMedia() 10.2 MediaDevices Interface Extensions 10.2.1 Methods getSupportedConstraints getUserMedia getUserMedia() 10.3 MediaStreamConstraints 10.3.1 Dictionary MediaStreamConstraints Members audio of type (boolean or MediaTrackConstraints), defaulting... video of type (boolean or MediaTrackConstraints), defaulting... 10.4 NavigatorUserMediaSuccessCallback 10.4.1 Callback NavigatorUserMediaSuccessCallback Parameters 10.5 NavigatorUserMediaErrorCallback 10.5.1 Callback NavigatorUserMediaErrorCallback Parameters 10.6 Implementation Suggestions Best Practice 1: Resource reservation Best Practice 2: Stored Permissions Best Practice 3: Handling multiple devices 11. Constrainable Pattern 11.1 Interface Definition 11.1.1 Attributes 11.1.2 Methods applyConstraints() settings dictionary fitness distance SelectSettings getCapabilities() getConstraints getSettings() 11.2 The Property Registry 11.2.1 Dictionary DoubleRange Members 11.2.2 Dictionary ConstrainDoubleRange Members 11.2.3 Dictionary LongRange Members 11.2.4 Dictionary ConstrainLongRange Members 11.2.5 Dictionary ConstrainBooleanParameters Members 11.2.6 Dictionary ConstrainDOMStringParameters Members 11.3 Capabilities Capabilities is a dictionary containing o... 11.3 Capabilities 11.4 Settings 11.5 Constraints and ConstraintSet 11.5.1 Dictionary Constraints Members 12. Examples 13. Privacy and Security Considerations 14. IANA Registrations 14.1 Track Constrainable Property Registrations sourceType deviceId groupId width height frameRate aspectRatio facingMode enum VideoFacingModeEnum { "user", "environment",... volume ConstrainDouble The volume or volume range, as a mul... sampleRate ConstrainLong The sample rate in samples per sec... sampleSize ConstrainLong The linear sample size in bits. Th... echoCancellation boolean When one or more audio streams is... 15. Change Log B. References B.1 Normative references [WEBIDL] B.2 Informative references
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Status:

open proposal pending resolved_yes resolved_no resolved_partial other assigned to Nobody Aboba, Bernard Alvestrand, Harald Bateman, Adrian Bergkvist, Adam Berkovitz, Joe Boström, Henrik Brandstetter, Taylor Bruaroey, Jan-Ivar Budigere Ramakrishna, Karthik Budkiewicz, Arnaud Burnett, Daniel Caddoux, Romain Carlson, Eric Casas-sanchez, Miguel Cazeaux, Stephane Chen, Qiang Chen, Soares CHIANG, MENG-JUE Choi, Soo-Hyun Cohen, Mark DADAS, Mohammed Dixit, Shwetank Druta, Dan Eriksson, Göran fablet, youenn Froehlich, Michael Garcia, Gustavo Gombos, Laszlo Gouaillard, Alexandre Griffin, Keith Guduru, Kiran Håkansson, Stefan Hancke, Philipp Hato, Jumpei Hazaël-Massieux, Dominique Hiron, Aurélien Hofman, Mathieu Huang, Xiaolu Huang, Zixia Hutton, Andrew Jägenstedt, Philip Jansson, Christoffer Jennings, Cullen Jesup, Randell Johnston, Alan Kang, Shin-Gak Kuo, Tzuhao Lacourba, Vivien Lee, Kangchan Lee, WonSuk Loreto, Salvatore Mandyam, Giridhar Manson, Rob Melo de Sales, Leandro Mészáros, Mihály mine, shingo Nakagawa, Koichi Nandakumar, Suhas Noble, Jer O'Connor, Theresa Pradhan, Manas Rescorla, Eric Roach, Adam Romascanu, Dan Sato, Toshimitsu Schulte, Lennart Schwartz, Ben SHIM, HyukHoon Sim, Sherwin Singer, David Singh, Varun Smith, Michael[tm] Soref, Josh Stojiljkovic, Aleksandar Sun, Shijun Terriberry, Timothy Thatcher, Peter Thomson, Martin Uberti, Justin Urdaneta, Guido Uysaler, Emircan Velayutham, Senthil Venisse, Emmanuel Yasskin, Jeffrey zhou, yubo Zhu, Jianjun

Type: substantive editorial typo question general comment undefined

Resolution status:

Response drafted Resolution implemented Reply sent to commenter

Response status:

No response from Commenter yet Commenter approved disposition Commenter objected to disposition
Commenter's response (URI):

Comment: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.

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WG Notes: This seems to have high complexity, but also value for many use cases. Is it possible to find extension points in the proposal so that these things can be added later without breaking the model?

Resolution: After discussions in the TF and with the commenter, two changes have been implemented: - Add a channel count for input devices (https://github.com/w3c/mediacapture-main/pull/210) - Add capability to discover input device capabilities via enumerateDevices (https://github.com/w3c/mediacapture-main/pull/211) Regarding output devices and capabilities, this is more in scope for the Audio Output Devices API document (https://github.com/w3c/mediacapture-output) and should be brought as comment to that document or alternatively as a proposed new document outlining a suitable API.

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