path: root/libavcodec/pcm_tablegen.h (plain)
blob: 7ce147f768b59d0a95d45298502b333215a0327b

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	{
107	build_xlaw_table(linear_to_alaw, alaw2linear, 0xd5);
108	}
109
110	static void pcm_ulaw_tableinit(void)
111	{
112	build_xlaw_table(linear_to_ulaw, ulaw2linear, 0xff);
113	}
114	#endif /* CONFIG_HARDCODED_TABLES */
115
116	#endif /* AVCODEC_PCM_TABLEGEN_H */
117