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Re: [mediacapture-image] "Implementation dependent" settings can't be made interoperable

From: Miguel Casas-Sanchez via GitHub <sysbot+gh@w3.org>
Date: Mon, 12 Dec 2016 22:26:39 +0000
To: public-media-capture-logs@w3.org
Message-ID: <issue_comment.created-266573048-1481581597-sysbot+gh@w3.org>
That's what the "Universal Serial Bus Device Class Definition for 
Video Devices Revision 1.5 August 9, 2012" gives us in e.g. its 
Section 4.2.2.3.2 Brightness Control: 
> This is used to specify the brightness. This is a relative value 
where increasing values indicate increasing brightness. The MIN and 
MAX values are sufficient to imply the resolution, so the RES value 
must always be 1. The MIN, MAX and default values are implementation 
dependent. This control must accept the GET_DEF request and return its
 default value.

Those four controls are just pass-through to UVC controls, so I don't 
see how this Spec can impose restrictions on them. FTR I've always 
seen those controls as a 0-255 scale, 128 being the middle value (i.e.
 it behaves as a signed char).  I'll add a comment with this info and 
link to the UVC standard. 

On the plus side, controls provide `max`,`min`, and `default` values, 
which would answer part of your question --  but now e.g. what would 
negative values do.

I wonder how other hardware-dependent Specs would tackle this problem.

-- 
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Received on Monday, 12 December 2016 22:26:45 UTC

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