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pcm_tablegen.h
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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 /* alaw2linear() - Convert an A-law value to 16-bit linear PCM */
40 static av_cold int alaw2linear(unsigned char a_val)
41 {
42  int t;
43  int seg;
44 
45  a_val ^= 0x55;
46 
47  t = a_val & QUANT_MASK;
48  seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
49  if(seg) t= (t + t + 1 + 32) << (seg + 2);
50  else t= (t + t + 1 ) << 3;
51 
52  return (a_val & SIGN_BIT) ? t : -t;
53 }
54 
55 static av_cold int ulaw2linear(unsigned char u_val)
56 {
57  int t;
58 
59  /* Complement to obtain normal u-law value. */
60  u_val = ~u_val;
61 
62  /*
63  * Extract and bias the quantization bits. Then
64  * shift up by the segment number and subtract out the bias.
65  */
66  t = ((u_val & QUANT_MASK) << 3) + BIAS;
67  t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
68 
69  return (u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS);
70 }
71 
72 #if CONFIG_HARDCODED_TABLES
73 #define pcm_alaw_tableinit()
74 #define pcm_ulaw_tableinit()
75 #include "libavcodec/pcm_tables.h"
76 #else
77 /* 16384 entries per table */
78 static uint8_t linear_to_alaw[16384];
79 static uint8_t linear_to_ulaw[16384];
80 
81 static av_cold void build_xlaw_table(uint8_t *linear_to_xlaw,
82  int (*xlaw2linear)(unsigned char),
83  int mask)
84 {
85  int i, j, v, v1, v2;
86 
87  j = 1;
88  linear_to_xlaw[8192] = mask;
89  for(i=0;i<127;i++) {
90  v1 = xlaw2linear(i ^ mask);
91  v2 = xlaw2linear((i + 1) ^ mask);
92  v = (v1 + v2 + 4) >> 3;
93  for(;j<v;j+=1) {
94  linear_to_xlaw[8192 - j] = (i ^ (mask ^ 0x80));
95  linear_to_xlaw[8192 + j] = (i ^ mask);
96  }
97  }
98  for(;j<8192;j++) {
99  linear_to_xlaw[8192 - j] = (127 ^ (mask ^ 0x80));
100  linear_to_xlaw[8192 + j] = (127 ^ mask);
101  }
102  linear_to_xlaw[0] = linear_to_xlaw[1];
103 }
104 
105 static void pcm_alaw_tableinit(void)
106 {
108 }
109 
110 static void pcm_ulaw_tableinit(void)
111 {
113 }
114 #endif /* CONFIG_HARDCODED_TABLES */
115 
116 #endif /* AVCODEC_PCM_TABLEGEN_H */
static void pcm_alaw_tableinit(void)
Definition: pcm_tablegen.h:105
static void pcm_ulaw_tableinit(void)
Definition: pcm_tablegen.h:110
static av_cold int ulaw2linear(unsigned char u_val)
Definition: pcm_tablegen.h:55
Macro definitions for various function/variable attributes.
uint8_t
#define av_cold
Definition: attributes.h:82
#define SEG_SHIFT
Definition: pcm_tablegen.h:34
static uint8_t linear_to_ulaw[16384]
Definition: pcm_tablegen.h:79
#define SEG_MASK
Definition: pcm_tablegen.h:35
static const uint16_t mask[17]
Definition: lzw.c:38
static av_cold void build_xlaw_table(uint8_t *linear_to_xlaw, int(*xlaw2linear)(unsigned char), int mask)
Definition: pcm_tablegen.h:81
#define BIAS
Definition: pcm_tablegen.h:37
static av_cold int alaw2linear(unsigned char a_val)
Definition: pcm_tablegen.h:40
#define SIGN_BIT
Definition: pcm_tablegen.h:31
#define QUANT_MASK
Definition: pcm_tablegen.h:32
static uint8_t linear_to_alaw[16384]
Definition: pcm_tablegen.h:78