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e0d49e2d3a
The original implementation of pac_find_sof() does not always find the Start Of Frame (SOF) marker. Replace it with a state machine based design. Acked-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Marton Nemeth <nm127@freemail.hu> Signed-off-by: Jean-Francois Moine <moinejf@free.fr> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
137 lines
3.6 KiB
C
137 lines
3.6 KiB
C
/*
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* Pixart PAC207BCA / PAC73xx common functions
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*
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* Copyright (C) 2008 Hans de Goede <j.w.r.degoede@hhs.nl>
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* Copyright (C) 2005 Thomas Kaiser thomas@kaiser-linux.li
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* Copyleft (C) 2005 Michel Xhaard mxhaard@magic.fr
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*
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* V4L2 by Jean-Francois Moine <http://moinejf.free.fr>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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*/
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/* We calculate the autogain at the end of the transfer of a frame, at this
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moment a frame with the old settings is being transmitted, and a frame is
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being captured with the old settings. So if we adjust the autogain we must
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ignore atleast the 2 next frames for the new settings to come into effect
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before doing any other adjustments */
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#define PAC_AUTOGAIN_IGNORE_FRAMES 3
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static const unsigned char pac_sof_marker[5] =
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{ 0xff, 0xff, 0x00, 0xff, 0x96 };
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/*
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The following state machine finds the SOF marker sequence
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0xff, 0xff, 0x00, 0xff, 0x96 in a byte stream.
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+----------+
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| 0: START |<---------------\
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+----------+<-\ |
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| \---/otherwise |
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v 0xff |
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+----------+ otherwise |
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| 1 |--------------->*
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| | ^
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+----------+ |
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| |
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v 0xff |
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+----------+<-\0xff |
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/->| |--/ |
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| | 2 |--------------->*
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| | | otherwise ^
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| +----------+ |
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| | |
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| v 0x00 |
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| +----------+ |
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| | 3 | |
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| | |--------------->*
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| +----------+ otherwise ^
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| | |
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0xff | v 0xff |
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| +----------+ |
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\--| 4 | |
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| |----------------/
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+----------+ otherwise
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v 0x96
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+----------+
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| FOUND |
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+----------+
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*/
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static unsigned char *pac_find_sof(struct gspca_dev *gspca_dev,
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unsigned char *m, int len)
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{
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struct sd *sd = (struct sd *) gspca_dev;
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int i;
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/* Search for the SOF marker (fixed part) in the header */
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for (i = 0; i < len; i++) {
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switch (sd->sof_read) {
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case 0:
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if (m[i] == 0xff)
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sd->sof_read = 1;
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break;
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case 1:
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if (m[i] == 0xff)
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sd->sof_read = 2;
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else
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sd->sof_read = 0;
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break;
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case 2:
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switch (m[i]) {
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case 0x00:
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sd->sof_read = 3;
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break;
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case 0xff:
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/* stay in this state */
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break;
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default:
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sd->sof_read = 0;
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}
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break;
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case 3:
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if (m[i] == 0xff)
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sd->sof_read = 4;
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else
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sd->sof_read = 0;
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break;
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case 4:
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switch (m[i]) {
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case 0x96:
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/* Pattern found */
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PDEBUG(D_FRAM,
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"SOF found, bytes to analyze: %u."
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" Frame starts at byte #%u",
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len, i + 1);
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sd->sof_read = 0;
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return m + i + 1;
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break;
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case 0xff:
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sd->sof_read = 2;
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break;
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default:
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sd->sof_read = 0;
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}
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break;
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default:
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sd->sof_read = 0;
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}
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}
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return NULL;
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}
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