2 * Header file for hardcoded PCM tables
4 * Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
6 * This file is part of FFmpeg.
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.
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.
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
23 #ifndef AVCODEC_PCM_TABLEGEN_H
24 #define AVCODEC_PCM_TABLEGEN_H
27 #include "libavutil/attributes.h"
29 /* from g711.c by SUN microsystems (unrestricted use) */
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. */
37 #define BIAS (0x84) /* Bias for linear code. */
40 * alaw2linear() - Convert an A-law value to 16-bit linear PCM
43 static av_cold
int alaw2linear(unsigned char a_val
)
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;
55 return (a_val
& SIGN_BIT
) ? t
: -t
;
58 static av_cold
int ulaw2linear(unsigned char u_val
)
62 /* Complement to obtain normal u-law value. */
66 * Extract and bias the quantization bits. Then
67 * shift up by the segment number and subtract out the bias.
69 t
= ((u_val
& QUANT_MASK
) << 3) + BIAS
;
70 t
<<= ((unsigned)u_val
& SEG_MASK
) >> SEG_SHIFT
;
72 return (u_val
& SIGN_BIT
) ? (BIAS
- t
) : (t
- BIAS
);
75 #if CONFIG_HARDCODED_TABLES
76 #define pcm_alaw_tableinit()
77 #define pcm_ulaw_tableinit()
78 #include "libavcodec/pcm_tables.h"
80 /* 16384 entries per table */
81 static uint8_t linear_to_alaw
[16384];
82 static uint8_t linear_to_ulaw
[16384];
84 static av_cold
void build_xlaw_table(uint8_t *linear_to_xlaw
,
85 int (*xlaw2linear
)(unsigned char),
93 v1
= xlaw2linear(i
^ mask
);
94 v2
= xlaw2linear((i
+ 1) ^ mask
);
95 v
= (v1
+ v2
+ 4) >> 3;
100 linear_to_xlaw
[8192 + j
] = (i
^ mask
);
102 linear_to_xlaw
[8192 - j
] = (i
^ (mask
^ 0x80));
105 linear_to_xlaw
[0] = linear_to_xlaw
[1];
108 static void pcm_alaw_tableinit(void)
110 build_xlaw_table(linear_to_alaw
, alaw2linear
, 0xd5);
113 static void pcm_ulaw_tableinit(void)
115 build_xlaw_table(linear_to_ulaw
, ulaw2linear
, 0xff);
117 #endif /* CONFIG_HARDCODED_TABLES */
119 #endif /* AVCODEC_PCM_TABLEGEN_H */