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Date: Sun, 30 Aug 2009 08:22:46 +0200
From: =?ISO-8859-2?Q?N=E9meth_M=E1rton?= <nm127@freemail.hu>
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To: Michel Xhaard <mxhaard@users.sourceforge.net>
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	=?ISO-8859-2?Q?N=E9me?= =?ISO-8859-2?Q?th_M=E1rton?=
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Subject: gspca_sunplus: problem with brightness control
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Hi,

I am using a "Trust 610 LCD Powerc@m Zoom" device in webcam mode
(USB ID=06d6:0031). I am running Linux 2.6.31-rc7 updated with the
http://linuxtv.org/hg/v4l-dvb repository at version 12564:6f58a5d8c7c6.

When I start watching to the webcam picture and change the brightness
value then I get the following result. The possible brigthness values
are between 0 and 255.

for i in $(seq 0 255); do echo $i; v4lctl bright $i; done

0: average image
 |
 | lighter images
 v
127: the most light image
 |
 | "jump" in brightness
 v
128: the most dark image
 |
 | lighter images
 v
255: average image

It seems to me that the values 128...255 are really negative numbers, so
the possible range should be between -128...127 (two's complement representation)
in case of this webcam.

Note that the contrast and color controls does not have any jump in
the range 0...255.

Regards,

	Márton Németh