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/*
* MR97310A decoder
*
* Copyright (C) 2004-2009 Theodore Kilgore <kilgota@auburn.edu>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin Street - Suite 500,
* Boston, MA 02111-1307, USA.
*/
#include <unistd.h>
#include "libv4lconvert-priv.h"
#include "libv4lsyscall-priv.h"
#define CLIP(x) ((x) < 0 ? 0 : ((x) > 0xff) ? 0xff : (x))
#define MIN_CLOCKDIV_CID V4L2_CID_PRIVATE_BASE
/* FIXME not threadsafe */
static int decoder_initialized;
static struct {
unsigned char is_abs;
unsigned char len;
signed char val;
} table[256];
static void init_mr97310a_decoder(void)
{
int i;
int is_abs, val, len;
for (i = 0; i < 256; ++i) {
is_abs = 0;
val = 0;
len = 0;
if ((i & 0x80) == 0) {
/* code 0 */
val = 0;
len = 1;
} else if ((i & 0xe0) == 0xc0) {
/* code 110 */
val = -3;
len = 3;
} else if ((i & 0xe0) == 0xa0) {
/* code 101 */
val = 3;
len = 3;
} else if ((i & 0xf0) == 0x80) {
/* code 1000 */
val = 8;
len = 4;
} else if ((i & 0xf0) == 0x90) {
/* code 1001 */
val = -8;
len = 4;
} else if ((i & 0xf0) == 0xf0) {
/* code 1111 */
val = -20;
len = 4;
} else if ((i & 0xf8) == 0xe0) {
/* code 11100 */
val = 20;
len = 5;
} else if ((i & 0xf8) == 0xe8) {
/* code 11101xxxxx */
is_abs = 1;
val = 0; /* value is calculated later */
len = 5;
}
table[i].is_abs = is_abs;
table[i].val = val;
table[i].len = len;
}
decoder_initialized = 1;
}
static inline unsigned char get_byte(const unsigned char *inp,
unsigned int bitpos)
{
const unsigned char *addr;
addr = inp + (bitpos >> 3);
return (addr[0] << (bitpos & 7)) | (addr[1] >> (8 - (bitpos & 7)));
}
int v4lconvert_decode_mr97310a(struct v4lconvert_data *data,
const unsigned char *inp, int src_size,
unsigned char *outp, int width, int height)
{
int row, col;
int val;
int bitpos;
unsigned char code;
unsigned char lp, tp, tlp, trp;
struct v4l2_control min_clockdiv = { .id = MIN_CLOCKDIV_CID };
if (!decoder_initialized)
init_mr97310a_decoder();
/* remove the header */
inp += 12;
bitpos = 0;
/* main decoding loop */
for (row = 0; row < height; ++row) {
col = 0;
/* first two pixels in first two rows are stored as raw 8-bit */
if (row < 2) {
code = get_byte(inp, bitpos);
bitpos += 8;
*outp++ = code;
code = get_byte(inp, bitpos);
bitpos += 8;
*outp++ = code;
col += 2;
}
while (col < width) {
/* get bitcode */
code = get_byte(inp, bitpos);
/* update bit position */
bitpos += table[code].len;
/* calculate pixel value */
if (table[code].is_abs) {
/* get 5 more bits and use them as absolute value */
code = get_byte(inp, bitpos);
val = (code & 0xf8);
bitpos += 5;
} else {
/* value is relative to top or left pixel */
val = table[code].val;
lp = outp[-2];
if (row > 1) {
tlp = outp[-2 * width - 2];
tp = outp[-2 * width];
trp = outp[-2 * width + 2];
}
if (row < 2) {
/* top row: relative to left pixel */
val += lp;
} else if (col < 2) {
/* left column: relative to top pixel */
/* initial estimate */
val += (tp + trp) / 2;
} else if (col > width - 3) {
/* left column: relative to top pixel */
val += (tp + lp + tlp + 1) / 3;
/* main area: weighted average of tlp, trp,
* lp, and tp */
} else {
tlp >>= 1;
trp >>= 1;
/* initial estimate for predictor */
val += (lp + tp + tlp + trp + 1) / 3;
}
}
/* store pixel */
*outp++ = CLIP(val);
++col;
}
/* src_size - 12 because of 12 byte footer */
if (((bitpos - 1) / 8) >= (src_size - 12)) {
data->frames_dropped++;
if (data->frames_dropped == 3) {
/* Tell the driver to go slower as
the compression engine is not able to
compress the image enough, we may
fail to do this because older
drivers don't support this */
SYS_IOCTL(data->fd, VIDIOC_G_CTRL,
&min_clockdiv);
min_clockdiv.value++;
SYS_IOCTL(data->fd, VIDIOC_S_CTRL,
&min_clockdiv);
/* We return success here, because if we
return failure for too many frames in a row
libv4l2 will return an error to the
application and some applications abort
on the first error received. */
data->frames_dropped = 0;
return 0;
}
V4LCONVERT_ERR("incomplete mr97310a frame\n");
return -1;
}
}
data->frames_dropped = 0;
return 0;
}
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