libavcodec/mlp.c

   1 /*
   2  * MLP codec common code
   3  * Copyright (c) 2007-2008 Ian Caulfield
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #include <stdint.h>
  23
  24 #include "libavutil/crc.h"
  25 #include "libavutil/intreadwrite.h"
  26 #include "mlp.h"
  27
  28 const uint8_t ff_mlp_huffman_tables[3][18][2] = {
  29     {    /* Huffman table 0, -7 - +10 */
  30         {0x01, 9}, {0x01, 8}, {0x01, 7}, {0x01, 6}, {0x01, 5}, {0x01, 4}, {0x01, 3},
  31         {0x04, 3}, {0x05, 3}, {0x06, 3}, {0x07, 3},
  32         {0x03, 3}, {0x05, 4}, {0x09, 5}, {0x11, 6}, {0x21, 7}, {0x41, 8}, {0x81, 9},
  33     }, { /* Huffman table 1, -7 - +8 */
  34         {0x01, 9}, {0x01, 8}, {0x01, 7}, {0x01, 6}, {0x01, 5}, {0x01, 4}, {0x01, 3},
  35         {0x02, 2}, {0x03, 2},
  36         {0x03, 3}, {0x05, 4}, {0x09, 5}, {0x11, 6}, {0x21, 7}, {0x41, 8}, {0x81, 9},
  37     }, { /* Huffman table 2, -7 - +7 */
  38         {0x01, 9}, {0x01, 8}, {0x01, 7}, {0x01, 6}, {0x01, 5}, {0x01, 4}, {0x01, 3},
  39         {0x01, 1},
  40         {0x03, 3}, {0x05, 4}, {0x09, 5}, {0x11, 6}, {0x21, 7}, {0x41, 8}, {0x81, 9},
  41     }
  42 };
  43
  44 static int crc_init = 0;
  45 static AVCRC crc_63[1024];
  46 static AVCRC crc_1D[1024];
  47 static AVCRC crc_2D[1024];
  48
  49 av_cold void ff_mlp_init_crc(void)
  50 {
  51     if (!crc_init) {
  52         av_crc_init(crc_63, 0,  8,   0x63, sizeof(crc_63));
  53         av_crc_init(crc_1D, 0,  8,   0x1D, sizeof(crc_1D));
  54         av_crc_init(crc_2D, 0, 16, 0x002D, sizeof(crc_2D));
  55         crc_init = 1;
  56     }
  57 }
  58
  59 uint16_t ff_mlp_checksum16(const uint8_t *buf, unsigned int buf_size)
  60 {
  61     uint16_t crc;
  62
  63     crc = av_crc(crc_2D, 0, buf, buf_size - 2);
  64     crc ^= AV_RL16(buf + buf_size - 2);
  65     return crc;
  66 }
  67
  68 uint8_t ff_mlp_checksum8(const uint8_t *buf, unsigned int buf_size)
  69 {
  70     uint8_t checksum = av_crc(crc_63, 0x3c, buf, buf_size - 1); // crc_63[0xa2] == 0x3c
  71     checksum ^= buf[buf_size-1];
  72     return checksum;
  73 }
  74
  75 uint8_t ff_mlp_restart_checksum(const uint8_t *buf, unsigned int bit_size)
  76 {
  77     int i;
  78     int num_bytes = (bit_size + 2) / 8;
  79
  80     int crc = crc_1D[buf[0] & 0x3f];
  81     crc = av_crc(crc_1D, crc, buf + 1, num_bytes - 2);
  82     crc ^= buf[num_bytes - 1];
  83
  84     for (i = 0; i < ((bit_size + 2) & 7); i++) {
  85         crc <<= 1;
  86         if (crc & 0x100)
  87             crc ^= 0x11D;
  88         crc ^= (buf[num_bytes] >> (7 - i)) & 1;
  89     }
  90
  91     return crc;
  92 }
  93
  94 uint8_t ff_mlp_calculate_parity(const uint8_t *buf, unsigned int buf_size)
  95 {
  96     uint32_t scratch = 0;
  97     const uint8_t *buf_end = buf + buf_size;
  98
  99     for (; ((intptr_t) buf & 3) && buf < buf_end; buf++)
 100         scratch ^= *buf;
 101     for (; buf < buf_end - 3; buf += 4)
 102         scratch ^= *((const uint32_t*)buf);
 103
 104     scratch = xor_32_to_8(scratch);
 105
 106     for (; buf < buf_end; buf++)
 107         scratch ^= *buf;
 108
 109     return scratch;
 110 }