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  1. /*
  2.  * Header file for hardcoded PCM tables
  3.  *
  4.  * Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
  5.  *
  6.  * This file is part of FFmpeg.
  7.  *
  8.  * FFmpeg is free software; you can redistribute it and/or
  9.  * modify it under the terms of the GNU Lesser General Public
  10.  * License as published by the Free Software Foundation; either
  11.  * version 2.1 of the License, or (at your option) any later version.
  12.  *
  13.  * FFmpeg is distributed in the hope that it will be useful,
  14.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16.  * Lesser General Public License for more details.
  17.  *
  18.  * You should have received a copy of the GNU Lesser General Public
  19.  * License along with FFmpeg; if not, write to the Free Software
  20.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21.  */
  22.  
  23. #ifndef AVCODEC_PCM_TABLEGEN_H
  24. #define AVCODEC_PCM_TABLEGEN_H
  25.  
  26. #include <stdint.h>
  27. #include "libavutil/attributes.h"
  28.  
  29. /* from g711.c by SUN microsystems (unrestricted use) */
  30.  
  31. #define         SIGN_BIT        (0x80)      /* Sign bit for a A-law byte. */
  32. #define         QUANT_MASK      (0xf)       /* Quantization field mask. */
  33. #define         NSEGS           (8)         /* Number of A-law segments. */
  34. #define         SEG_SHIFT       (4)         /* Left shift for segment number. */
  35. #define         SEG_MASK        (0x70)      /* Segment field mask. */
  36.  
  37. #define         BIAS            (0x84)      /* Bias for linear code. */
  38.  
  39. /*
  40.  * alaw2linear() - Convert an A-law value to 16-bit linear PCM
  41.  *
  42.  */
  43. static av_cold int alaw2linear(unsigned char a_val)
  44. {
  45.         int t;
  46.         int seg;
  47.  
  48.         a_val ^= 0x55;
  49.  
  50.         t = a_val & QUANT_MASK;
  51.         seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
  52.         if(seg) t= (t + t + 1 + 32) << (seg + 2);
  53.         else    t= (t + t + 1     ) << 3;
  54.  
  55.         return (a_val & SIGN_BIT) ? t : -t;
  56. }
  57.  
  58. static av_cold int ulaw2linear(unsigned char u_val)
  59. {
  60.         int t;
  61.  
  62.         /* Complement to obtain normal u-law value. */
  63.         u_val = ~u_val;
  64.  
  65.         /*
  66.          * Extract and bias the quantization bits. Then
  67.          * shift up by the segment number and subtract out the bias.
  68.          */
  69.         t = ((u_val & QUANT_MASK) << 3) + BIAS;
  70.         t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
  71.  
  72.         return (u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS);
  73. }
  74.  
  75. #if CONFIG_HARDCODED_TABLES
  76. #define pcm_alaw_tableinit()
  77. #define pcm_ulaw_tableinit()
  78. #include "libavcodec/pcm_tables.h"
  79. #else
  80. /* 16384 entries per table */
  81. static uint8_t linear_to_alaw[16384];
  82. static uint8_t linear_to_ulaw[16384];
  83.  
  84. static av_cold void build_xlaw_table(uint8_t *linear_to_xlaw,
  85.                              int (*xlaw2linear)(unsigned char),
  86.                              int mask)
  87. {
  88.     int i, j, v, v1, v2;
  89.  
  90.     j = 0;
  91.     for(i=0;i<128;i++) {
  92.         if (i != 127) {
  93.             v1 = xlaw2linear(i ^ mask);
  94.             v2 = xlaw2linear((i + 1) ^ mask);
  95.             v = (v1 + v2 + 4) >> 3;
  96.         } else {
  97.             v = 8192;
  98.         }
  99.         for(;j<v;j++) {
  100.             linear_to_xlaw[8192 + j] = (i ^ mask);
  101.             if (j > 0)
  102.                 linear_to_xlaw[8192 - j] = (i ^ (mask ^ 0x80));
  103.         }
  104.     }
  105.     linear_to_xlaw[0] = linear_to_xlaw[1];
  106. }
  107.  
  108. static void pcm_alaw_tableinit(void)
  109. {
  110.     build_xlaw_table(linear_to_alaw, alaw2linear, 0xd5);
  111. }
  112.  
  113. static void pcm_ulaw_tableinit(void)
  114. {
  115.     build_xlaw_table(linear_to_ulaw, ulaw2linear, 0xff);
  116. }
  117. #endif /* CONFIG_HARDCODED_TABLES */
  118.  
  119. #endif /* AVCODEC_PCM_TABLEGEN_H */
  120.