ffmpeg/libavcodec/pcm_tablegen.h

   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 */