The MediaTrackSupportedConstraints
dictionary establishes the list of constrainable properties recognized by the user agent or browser in its implementation of the MediaStreamTrack
object. An object conforming to MediaTrackSupportedConstraints
is returned by MediaDevices.getSupportedConstraints()
.
Because of the way interface definitions in WebIDL work, if a constraint is requested but not supported, no error will occur. Instead, the specified constraints will be applied, with any unrecognized constraints stripped from the request. That can lead to confusing and hard to debug errors, so be sure to use getSupportedConstraints()
to retrieve this information before attempting to establish constraints if you need to know the difference between silently ignoring a constraint and a constraint being accepted.
An actual constraint set is described using an object based on the MediaTrackConstraints
dictionary.
To learn more about how constraints work, see Capabilities, constraints, and settings.
Some combination—but not necessarily all—of the following properties will exist on the object.
autoGainControl
-
A Boolean whose value is true
if the autoGainControl
constraint is supported in the current environment.
width
-
A Boolean value whose value is true
if the width
constraint is supported in the current environment.
height
-
A Boolean value whose value is true
if the height
constraint is supported in the current environment.
aspectRatio
-
A Boolean value whose value is true
if the aspectRatio
constraint is supported in the current environment.
frameRate
-
A Boolean value whose value is true
if the frameRate
constraint is supported in the current environment.
facingMode
-
A Boolean value whose value is true
if the facingMode
constraint is supported in the current environment.
resizeMode
-
A Boolean value whose value is true
if the resizeMode
constraint is supported in the current environment.
-
volume
Deprecated Non-standard
-
A Boolean value whose value is true
if the volume
constraint is supported in the current environment.
sampleRate
-
A Boolean value whose value is true
if the sampleRate
constraint is supported in the current environment.
sampleSize
-
A Boolean value whose value is true
if the sampleSize
constraint is supported in the current environment.
echoCancellation
-
A Boolean value whose value is true
if the echoCancellation
constraint is supported in the current environment.
latency
-
A Boolean value whose value is true
if the latency
constraint is supported in the current environment.
noiseSuppression
-
A Boolean whose value is true
if the noiseSuppression
constraint is supported in the current environment.
channelCount
-
A Boolean value whose value is true
if the channelCount
constraint is supported in the current environment.
deviceId
-
A Boolean value whose value is true
if the deviceId
constraint is supported in the current environment.
groupId
-
A Boolean value whose value is true
if the groupId
constraint is supported in the current environment.
For tracks containing video sources from the user's screen contents, the following additional properties are may be included in addition to those available for video tracks.
displaySurface
-
A Boolean value which is true
if the displaySurface
constraint is supported in the current environment.
logicalSurface
-
A Boolean value which is true
if the logicalSurface
constraint is supported in the current environment.