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Re: [depth] depth value encoding proposal

From: Kostiainen, Anssi <anssi.kostiainen@intel.com>
Date: Tue, 19 Aug 2014 14:58:46 +0000
To: Benjamin Schwartz <bemasc@google.com>
CC: "Hu, Ningxin" <ningxin.hu@intel.com>, "public-media-capture@w3.org" <public-media-capture@w3.org>, Rob Manson <roBman@buildar.com>
Message-ID: <0E3BD87D-FF85-492C-BC7F-8BE68895F7BF@intel.com>
Hi Benjamin,

Thanks for your comments, and sorry for the late reply due to the vacation period.

I noticed the following comments (1) and (2) you’ve made, and would like to check the status, and ask your help to fill in the gaps if any:

(1) "I do not think this kind of arbitrary mapping is appropriate in a W3C standard.  We should arrange for a natural representation instead, with modifications to Canvas and WebGL if necessary.” [1]

To make sure I understood this correctly:

Firstly, you're proposing we patch the CanvasRenderingContext2D and make ImageData.data of type ArrayBufferView instead of Uint8ClampedArray to allow the Uint16Array type, correct? Better suggestions?

Secondly, extend the WebGLRenderingContext along the lines of the LUMINANCE16 extension proposal [2] -- or would you prefer to use the depth component of a GL texture as you previously suggested? Known issues? I’d like to hear your latest thoughts on this and if possible a concrete proposal how you’d prefer this to be spec’d to be practical for developers and logical for implementers.

(2) "I don't think getDepthTracks() should return color-video.  If you want to prototype using depth-to-color mappings, the logical way is to treat the depth channel as a distinct color video camera, accessible by the usual device selection mechanisms.” [3]

This is what the spec currently says re getDepthTracks():


The getDepthTracks() method, when invoked, must return a sequence of MediaStreamTrack objects representing the depth tracks in this stream.

The getDepthTracks() method must return a sequence that represents a snapshot of all the MediaStreamTrack objects in this stream's track set whose kind is equal to "depth". The conversion from the track set to the sequence is user agent defined and the order does not have to be stable between calls.


Do you have a concrete proposal how you’d tighten the prose to clear the confusion?

[Btw. we’ll track open issues for this spec using GH issues [4] to make sure we don’t miss any of the feedback.]



[1] http://lists.w3.org/Archives/Public/public-media-capture/2014Jul/0087.html
[2] https://www.khronos.org/bugzilla/show_bug.cgi?id=407
[3] http://lists.w3.org/Archives/Public/public-media-capture/2014Jul/0091.html
[4] https://github.com/w3c/mediacapture-depth/issues
Received on Tuesday, 19 August 2014 15:01:46 UTC

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