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V4L/DVB (8870): gspca: Fix dark room problem with sonixb. 

When using the sonixb driver in a dark room and given that the autoexposure
algorithm starts with a setting most suitable for daylight, the picture
produced by the cam may actually be 100% black leading to a avg_lum value of 0,
so an avg_lum value of 0 does not always signal an exposure settings change
(which it normally does). This patch adds a check for the really black image
case and stops dropping all frames as invalid in this case.

Signed-off-by: Hans de Goede <j.w.r.degoede@hhs.nl>
Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Hans de Goede 2008-09-04 16:22:56 -03:00 committed by Mauro Carvalho Chehab
parent a94a508691
commit bf2a2202f7
1 changed files with 12 additions and 2 deletions
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14
drivers/media/video/gspca/sonixb.c
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@ -52,6 +52,7 @@ MODULE_LICENSE("GPL");
struct sd {
struct gspca_dev gspca_dev; /* !! must be the first item */
atomic_t avg_lum;
int prev_avg_lum;
unsigned char gain;
unsigned char exposure;
@ -1022,10 +1023,19 @@ static void sd_pkt_scan(struct gspca_dev *gspca_dev,
} else {
lum = data[i + 8] + (data[i + 9] << 8);
}
if (lum == 0) {
/* When exposure changes midway a frame we
get a lum of 0 in this case drop 2 frames
as the frames directly after an exposure
change have an unstable image. Sometimes lum
*really* is 0 (cam used in low light with
low exposure setting), so do not drop frames
if the previous lum was 0 too. */
if (lum == 0 && sd->prev_avg_lum != 0) {
lum = -1;
sd->frames_to_drop = 2;
}
sd->prev_avg_lum = 0;
} else
sd->prev_avg_lum = lum;
atomic_set(&sd->avg_lum, lum);
if (sd->frames_to_drop) {