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pcm_tablegen.h (4275B)

      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 #define         VIDC_SIGN_BIT    (1)
     40 #define         VIDC_QUANT_MASK  (0x1E)
     41 #define         VIDC_QUANT_SHIFT (1)
     42 #define         VIDC_SEG_SHIFT   (5)
     43 #define         VIDC_SEG_MASK    (0xE0)
     44 
     45 /* alaw2linear() - Convert an A-law value to 16-bit linear PCM */
     46 static av_cold int alaw2linear(unsigned char a_val)
     47 {
     48    int t;
     49    int seg;
     50 
     51    a_val ^= 0x55;
     52 
     53    t = a_val & QUANT_MASK;
     54    seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
     55    if(seg) t= (t + t + 1 + 32) << (seg + 2);
     56    else    t= (t + t + 1     ) << 3;
     57 
     58    return (a_val & SIGN_BIT) ? t : -t;
     59 }
     60 
     61 static av_cold int ulaw2linear(unsigned char u_val)
     62 {
     63    int t;
     64 
     65    /* Complement to obtain normal u-law value. */
     66    u_val = ~u_val;
     67 
     68    /*
     69     * Extract and bias the quantization bits. Then
     70     * shift up by the segment number and subtract out the bias.
     71     */
     72    t = ((u_val & QUANT_MASK) << 3) + BIAS;
     73    t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
     74 
     75    return (u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS);
     76 }
     77 
     78 static av_cold int vidc2linear(unsigned char u_val)
     79 {
     80    int t;
     81 
     82    /*
     83     * Extract and bias the quantization bits. Then
     84     * shift up by the segment number and subtract out the bias.
     85     */
     86    t = (((u_val & VIDC_QUANT_MASK) >> VIDC_QUANT_SHIFT) << 3) + BIAS;
     87    t <<= ((unsigned)u_val & VIDC_SEG_MASK) >> VIDC_SEG_SHIFT;
     88 
     89    return (u_val & VIDC_SIGN_BIT) ? (BIAS - t) : (t - BIAS);
     90 }
     91 
     92 #if CONFIG_HARDCODED_TABLES
     93 #define pcm_alaw_tableinit()
     94 #define pcm_ulaw_tableinit()
     95 #define pcm_vidc_tableinit()
     96 #include "libavcodec/pcm_tables.h"
     97 #else
     98 /* 16384 entries per table */
     99 static uint8_t linear_to_alaw[16384];
    100 static uint8_t linear_to_ulaw[16384];
    101 static uint8_t linear_to_vidc[16384];
    102 
    103 static av_cold void build_xlaw_table(uint8_t *linear_to_xlaw,
    104                             int (*xlaw2linear)(unsigned char),
    105                             int mask)
    106 {
    107    int i, j, v, v1, v2;
    108 
    109    j = 1;
    110    linear_to_xlaw[8192] = mask;
    111    for(i=0;i<127;i++) {
    112        v1 = xlaw2linear(i ^ mask);
    113        v2 = xlaw2linear((i + 1) ^ mask);
    114        v = (v1 + v2 + 4) >> 3;
    115        for(;j<v;j+=1) {
    116            linear_to_xlaw[8192 - j] = (i ^ (mask ^ 0x80));
    117            linear_to_xlaw[8192 + j] = (i ^ mask);
    118        }
    119    }
    120    for(;j<8192;j++) {
    121        linear_to_xlaw[8192 - j] = (127 ^ (mask ^ 0x80));
    122        linear_to_xlaw[8192 + j] = (127 ^ mask);
    123    }
    124    linear_to_xlaw[0] = linear_to_xlaw[1];
    125 }
    126 
    127 static void pcm_alaw_tableinit(void)
    128 {
    129    build_xlaw_table(linear_to_alaw, alaw2linear, 0xd5);
    130 }
    131 
    132 static void pcm_ulaw_tableinit(void)
    133 {
    134    build_xlaw_table(linear_to_ulaw, ulaw2linear, 0xff);
    135 }
    136 
    137 static void pcm_vidc_tableinit(void)
    138 {
    139    build_xlaw_table(linear_to_vidc, vidc2linear, 0xff);
    140 }
    141 #endif /* CONFIG_HARDCODED_TABLES */
    142 
    143 #endif /* AVCODEC_PCM_TABLEGEN_H */