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/*
* Pixart PAC207BCA / PAC73xx common functions
*
* Copyright (C) 2008 Hans de Goede <j.w.r.degoede@hhs.nl>
* Copyright (C) 2005 Thomas Kaiser thomas@kaiser-linux.li
* Copyleft (C) 2005 Michel Xhaard mxhaard@magic.fr
*
* V4L2 by Jean-Francois Moine <http://moinejf.free.fr>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
/* We calculate the autogain at the end of the transfer of a frame, at this
moment a frame with the old settings is being transmitted, and a frame is
being captured with the old settings. So if we adjust the autogain we must
ignore atleast the 2 next frames for the new settings to come into effect
before doing any other adjustments */
#define PAC_AUTOGAIN_IGNORE_FRAMES 3
static const unsigned char pac_sof_marker[5] =
{ 0xff, 0xff, 0x00, 0xff, 0x96 };
/*
The following state machine finds the SOF marker sequence
0xff, 0xff, 0x00, 0xff, 0x96 in a byte stream.
+----------+
| 0: START |<---------------\
+----------+<-\ |
| \---/otherwise |
v 0xff |
+----------+ otherwise |
| 1 |--------------->*
| | ^
+----------+ |
| |
v 0xff |
+----------+<-\0xff |
/->| |--/ |
| | 2 |--------------->*
| | | otherwise ^
| +----------+ |
| | |
| v 0x00 |
| +----------+ |
| | 3 | |
| | |--------------->*
| +----------+ otherwise ^
| | |
0xff | v 0xff |
| +----------+ |
\--| 4 | |
| |----------------/
+----------+ otherwise
|
v 0x96
+----------+
| FOUND |
+----------+
*/
static unsigned char *pac_find_sof(struct gspca_dev *gspca_dev,
unsigned char *m, int len)
{
struct sd *sd = (struct sd *) gspca_dev;
int i;
/* Search for the SOF marker (fixed part) in the header */
for (i = 0; i < len; i++) {
switch (sd->sof_read) {
case 0:
if (m[i] == 0xff)
sd->sof_read = 1;
break;
case 1:
if (m[i] == 0xff)
sd->sof_read = 2;
else
sd->sof_read = 0;
break;
case 2:
switch (m[i]) {
case 0x00:
sd->sof_read = 3;
break;
case 0xff:
/* stay in this state */
break;
default:
sd->sof_read = 0;
}
break;
case 3:
if (m[i] == 0xff)
sd->sof_read = 4;
else
sd->sof_read = 0;
break;
case 4:
switch (m[i]) {
case 0x96:
/* Pattern found */
PDEBUG(D_FRAM,
"SOF found, bytes to analyze: %u."
" Frame starts at byte #%u",
len, i + 1);
sd->sof_read = 0;
return m + i + 1;
break;
case 0xff:
sd->sof_read = 2;
break;
default:
sd->sof_read = 0;
}
break;
default:
sd->sof_read = 0;
}
}
return NULL;
}
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