Re: [mediacapture-image] Add pan and tilt constraints

> I'm not sure whether W3C APIs should be tailored for particular brand or type of device.

I'm not trying to tailor it to a particular brand or type of device, I was simply using a popular consumer brand as a way to gauge how common the roll control is in the wild.

> I think it is not related to arcseconds or degrees, it is generic rounding problem.

It's a generic problem with floats, but the conversion from arcseconds to degrees is what causes it to be more prevalent than it would be for other controls. Most other controls are integers, or have a couple decimal places. The conversion from arcseconds to degrees (dividing by 3600) leads to repeating decimals like the one in my example, which are likely to run into the rounding issue.

So while not specific to arcseconds, by their nature you're more likely to run into repeating decimals due to the conversion.

I won't put up too much of a fight here, I just think a spec should do its best to protect users from sharp edges if possible.

> @dsanders11 my personal opinion is that pan, tilt and roll are niche features and not directly related to photo / video capture capabilities. Those are the features of camera accesoires: motorized heads, 3-axis gimbals, conference webcam or security IP cams chassis. Looks like UVC and Windows APIs have those features for some legacy reasons, I'm not sure whether new specs should replicate same pattern.

I disagree with this assessment. They are not features limited to those listed camera accessories, they are features supported by many off the shelf webcams, of various brands, just not as common on cameras in tiny packages like phones or tablets. Roll is the more niche feature, which is why this PR is only for pan and tilt to begin with.

If you Google search [`"bmControls" pantilt`](https://www.google.com/search?q="bmControls"+pantilt) you can see some of the various webcams that support pan and tilt thanks to people posting the output of `lsusb` online. Webcams I've identified that support pan and tilt (but not roll) in about 5 minutes of looking:

* [vendorId: Acer (probably builtin laptop webcam)](https://mail.gnome.org/archives/ekiga-list/2015-April/msg00013.html)
* [HP Webcam HD 5210](http://buttersideup.com/files/hp-5210-lsusb.txt)
* [vendorId: Lenovo (probably builtin laptop webcam)](http://webcache.googleusercontent.com/search?q=cache:6uL8U1VpjSwJ:www.os2world.com/forum/index.php%3Faction%3Ddlattach%3Btopic%3D196.0%3Battach%3D228+&cd=7&hl=en&ct=clnk&gl=us)
* [Dell Inspiron 1520 builtin webcam](https://forums.virtualbox.org/viewtopic.php?f=2&t=3740)
* [Microsoft LifeCam HD-3000](https://6xq.net/webcam-firmware/hd3000_lsusb.txt)
* A dozen different models of Logitech webcams

I believe there to be broad support for pan and tilt among laptop integrated webcams and external USB webcams, without any sort of accessory required.

@dsanders11 my personal opinion is that pan, tilt and roll are niche features and not directly related to photo / video capture capabilities.

Pan and tilt, especially when paired with zoom, have good applicability for use with face tracking, eye tracking, and other such use cases.

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Received on Friday, 16 June 2017 17:30:02 UTC