Add Intel Perceptual Computing SDK based depth video capture for Windows

Add Intel Perceptual Computing SDK based depth video capture for Windows

Intel Perceptual Computing SDK [1] supports to obtain depth images
from depth cameras. Each pixel in depth image is a 16bits integer
value which indicates the distance from an object to the camera's
XY plane.

When depth camera is available, VideoCaptureDevicePXCWin adds a
extra "depth" camera after the "normal" ones which are backed by
VideoCaptureDeviceWin or VideoCaptureDeviceMFWin.

The depth value is encoded in Y plane (8bits) in YV12 image format.
The 16bits to 8bits conversion is based on tone mapping [2] which
aligns with the depth encoding for Tango smartphone's depth camera
in VideoCaptureTango.java.

Currently, this feature is behind "enable-depth-camera" flag.

Tested via [3], click on GetDevices, then open "depth" camera.

[1] https://software.intel.com/en-us/node/391067
[2] http://en.wikipedia.org/wiki/Tone_mapping
[3] https://src.chromium.org/svn/trunk/src/chrome/test/data/webrtc/manual/peerconnection.html

BUG=369849

[mcasas, 2014-05-07 11:49:21]

drive-by from the Issue description:

This looks to me like a good idea but we shouldn't need to add the headers and
library to Chromium just for this. 

If you want to land this, which I encourage you to, the idea would be to do
something similar to AVFoundation library for Mac:
- prepare a pcx_glue.{h,cc}
- in it, load the library via dylib [1], check that it goes fine etc
- add all the pcx symbols you need as glue symbols, implemented as "forwarders"
[2] (ignore the mac-specific syntax in this reference).


[1]
https://code.google.com/p/chromium/codesearch#chromium/src/media/video/captur...

[2]
https://code.google.com/p/chromium/codesearch#chromium/src/media/video/captur...

[nhu, 2014-05-08 06:59:47]

@mcasas, thanks for the suggestion. I will try the pxc_glue solution. 

In AVFoundation glue, some codes are from AVFoundation headers, right? If true,
I also need to copy some codes (symbols, structure/class definitions) from
PCSDK's headers into the PXC library glue. I am going to check with Intel PCSDK
team whether there are any license concerns.

[mcasas, 2014-05-08 14:00:07]

On 2014/05/08 06:59:47, nhu wrote:
> @mcasas, thanks for the suggestion. I will try the pxc_glue solution. 
> 
> In AVFoundation glue, some codes are from AVFoundation headers, right? If
true,
> I also need to copy some codes (symbols, structure/class definitions) from
> PCSDK's headers into the PXC library glue. I am going to check with Intel
PCSDK
> team whether there are any license concerns.

Every class coming out of AVFoundation, f.e. AVCaptureDevice, is 
wrapped with a Chrome version, i.e. CrAVCaptureDevice, which 
forwards to it [1].
The structures are indeed copied quoting where
they stem from [2].

[1]
https://code.google.com/p/chromium/codesearch#chromium/src/media/video/captur...
[2]
https://code.google.com/p/chromium/codesearch#chromium/src/media/video/captur...