- From: <bugzilla@jessica.w3.org>
- Date: Mon, 25 Aug 2014 10:33:22 +0000
- To: public-media-capture@w3.org
https://www.w3.org/Bugs/Public/show_bug.cgi?id=26654
Bug ID: 26654
Summary: WebIDL types needed in Constrainable application
Product: WebRTC Working Group
Version: unspecified
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P2
Component: Media Capture and Streams
Assignee: public-media-capture@w3.org
Reporter: harald@alvestrand.no
CC: public-media-capture@w3.org
>From Jan-Ivar, pointing out several issues with the Constrainable pattern as
applied to MediaTrack:
The spec still leaves several types to be inferred by the implementer around
constraints:
1. In [1]:
> partial interface MediaDevices {
> static Dictionary getSupportedConstraints (DOMString kind);
"Dictionary" is not defined. To implement this, we'd need something like:
dictionary SupportedMediaTrackConstraintSet {
boolean width;
boolean height;
boolean aspectRatio;
boolean frameRate;
boolean facingMode;
boolean volume;
boolean sampleRate;
boolean sampleSize;
boolean echoCancelation;
boolean sourceId;
boolean groupId;
// basically a boolean rehash of MediaTrackConstraintSet
};
static SupportedMediaTrackConstraintSet getSupportedConstraints (DOMString
kind);
or simply:
static MediaTrackConstraintSet getSupportedConstraints (DOMString kind);
since UAs can return non-zero values in MediaTrackConstraintSet just fine!
2. In [2]:
> interface MediaStreamTrack : EventTarget {
> ...
> Capabilities getCapabilities ();
> MediaTrackConstraints getConstraints ();
> Settings getSettings ();
Capabilities and Settings are not defined in this use of the Constrainable
pattern. To implement this, we'd need something like:
dictionary MediaTrackSettingSet {
long width;
long height;
double aspectRatio;
double frameRate;
VideoFacingMode facingMode;
double volume;
long sampleRate;
long sampleSize;
boolean echoCancelation;
DOMString sourceId;
DOMString groupId;
// basically a bare-value rehash of MediaTrackConstraintSet
};
interface MediaStreamTrack : EventTarget {
...
MediaTrackConstraintSet getCapabilities ();
MediaTrackConstraints getConstraints ();
MediaTrackSettingSet getSettings ();
or simply:
interface MediaStreamTrack : EventTarget {
...
MediaTrackConstraintSet getCapabilities ();
MediaTrackConstraints getConstraints ();
MediaTrackConstraintSet getSettings ();
since UAs can return bare values in MediaTrackConstraintSet just fine!
3. In the Constrainable Pattern in [3]:
> Capabilities are dictionary containing one or more key-value pairs, where each key must be a constrainable property defined in the registry, and each value must be a subset of the set of values defined for that property in the registry. The exact syntax of the value expression depends on the type of the property but is of type ConstraintValues . The Capabilities dictionary specifies the subset of the constrainable properties and values from the registry that the UA supports.
Typo: "Capabilities are dictionary" -> "Capabilities is a dictionary".
Importantly, all capabilities are in one dictionary.
The type "ConstraintValues" is not defined anywhere. Do we mean "members of
ConstraintSet" here? If so, that makes Capabilities of type ConstraintSet, yet
we're leaving that deduction to the reader. IMHO prose and examples are no
substitute for definitions.
4. In the Constrainable Pattern in [4]:
> A Setting is a dictionary containing one or more key-value pairs. It must contain each key returned in getCapabilities(). There must be a single value for each key and the value must a member of the set defined for that property by capabilities(). The Settings dictionary contains the actual values that the UA has chosen for the object's Capabilities. The exact syntax of the value depends on the type of the property.
Typo: "A Setting is a dictionary" -> "Settings is a dictionary". Importantly,
all settings are in one dictionary.
Typo: "the value must a member" -> "the value must be a member"
We're leaving the reader to deduce that Settings is a bare-values-only subset
of ConstraintSet. IMHO prose and examples are no substitute for definitions.
5. In the Constrainable Pattern in [5]:
> typedef Dictionary ConstraintSet;
"Dictionary" is not defined, and even if it were, it wouldn't have the right
members, so a typedef infers the wrong thing. We could say:
dictionary ConstraintSet { /* members */ };
6. In [6]:
> dictionary MediaTrackConstraintSet {
> ConstrainLong width;
> ConstrainLong height;
> ConstrainDouble aspectRatio;
> ConstrainDouble frameRate;
> ConstrainVideoFacingMode facingMode;
> ConstrainDouble volume;
> ConstrainLong sampleRate;
> ConstrainLong sampleSize;
> boolean echoCancelation;
> ConstrainDOMString sourceId;
> DOMString groupId;
> };
groupId seems to have the wrong type. Why not ConstrainDOMString groupId ?
.: Jan-Ivar :.
[1]
http://dev.w3.org/2011/webrtc/editor/archives/20140817/getusermedia.html#mediadevices-interface-extensions
[2]
http://dev.w3.org/2011/webrtc/editor/archives/20140817/getusermedia.html#media-stream-track-interface-definition
[3]
http://dev.w3.org/2011/webrtc/editor/archives/20140817/getusermedia.html#capabilities
[4]
http://dev.w3.org/2011/webrtc/editor/archives/20140817/getusermedia.html#settings
[5]
http://dev.w3.org/2011/webrtc/editor/archives/20140817/getusermedia.html#constraints
[6]
http://dev.w3.org/2011/webrtc/editor/archives/20140817/getusermedia.html#dictionary-mediatrackconstraints-members
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Received on Monday, 25 August 2014 10:33:23 UTC