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Diffstat (limited to 'v4l2-apps/libv4l/libv4lconvert/mr97310a.c')
| -rw-r--r-- | v4l2-apps/libv4l/libv4lconvert/mr97310a.c | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/v4l2-apps/libv4l/libv4lconvert/mr97310a.c b/v4l2-apps/libv4l/libv4lconvert/mr97310a.c new file mode 100644 index 000000000..b5dbea7e6 --- /dev/null +++ b/v4l2-apps/libv4l/libv4lconvert/mr97310a.c @@ -0,0 +1,169 @@ +/* + * MR97310A decoder + * + * Copyright (C) 2004 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., 59 Temple Place - Suite 330, + * Boston, MA 02111-1307, USA. + */ + +#include "libv4lconvert-priv.h" + +#define CLIP(x) ((x)<0?0:((x)>0xff)?0xff:(x)) + +/* FIXME not threadsafe */ +static int decoder_initialized = 0; + +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 = +7; + len = 4; + } else if ((i & 0xf0) == 0x90) { + /* code 1001 */ + val = -7; + len = 4; + } else if ((i & 0xf0) == 0xf0) { + /* code 1111 */ + val = -15; + len = 4; + } else if ((i & 0xf8) == 0xe0) { + /* code 11100 */ + val = +15; + 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))); +} + +void v4lconvert_decode_mr97310a(const unsigned char *inp, unsigned char *outp, + int width, int height) +{ + int row, col; + int val; + int bitpos; + unsigned char code; + unsigned char lp, tp, tlp, trp; + + if (!decoder_initialized) + init_mr97310a_decoder(); + + 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 += (2*tp + 2*trp + 1)/4; + } else if (col > width - 3) { + /* left column: relative to top pixel */ + val += (2*tp + 2*tlp + 1)/4; + /* main area: average of left and top pixel */ + } else { + /* initial estimate for predictor */ + val += (2*lp + tp + trp + 1)/4; + } + } + /* store pixel */ + *outp++ = CLIP(val); + ++col; + } + } + + return; +} |