Re: [mediacapture-image] Ignore PTZ request if no PTZ camera (#246)

What exactly should be ignored?

If a web site calls `navigator.mediaDevices.getUserMedia({video: {pan: {}}})` and there are no PTZ cameras, the permission request will be `{name: "camera", panTiltZoom: false}` (instead of `{name: "camera", panTiltZoom: true}`) and what should happen then? Should the `pan: {}` part be completely ignored (an empty ConstrainDoubleRange value implies no constraints per the spec)?
At the moment Chrome implements the permission ignorance part but throws an OvercontstrainedError which does not make sense.

What if a web site calls `navigator.mediaDevices.getUserMedia({video: {pan: {ideal: 0}}})` and there are no PTZ cameras? Should be `pan: {ideal: 0}` part be completely ignored or should the [fitness distance](https://w3c.github.io/mediacapture-main/#dfn-fitness-distance) be 0 because a pan constraint does not apply to non-PTZ cameras? This choice has no effect to the selected device but affects how this should be specified in the spec. Or should the [fitness distance](https://w3c.github.io/mediacapture-main/#dfn-fitness-distance) be positive infinity because there is no actual pan setting? This would cause all non-PTZ cameras to be ignored and an OverconstrainedError to be thrown.

What if a web site calls `navigator.mediaDevices.getUserMedia({video: {pan: {exact: 0}}})`, `navigator.mediaDevices.getUserMedia({video: {pan: {max: 0}}})` or `navigator.mediaDevices.getUserMedia({video: {pan: {min: 0}}})` and there are no PTZ cameras? Should be `pan: {exact: 0}` et al parts be completely ignored or should the [fitness distance](https://w3c.github.io/mediacapture-main/#dfn-fitness-distance) be positive infinity because the settings dictionary's (missing) value for the constraint does not satisfy the constraint?

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Received on Monday, 31 August 2020 12:22:09 UTC