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ffmpeg / libavcodec / pcm_tablegen.h @ 2912e87a

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/*
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 * Header file for hardcoded PCM tables
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 *
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 * Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
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 *
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 * This file is part of Libav.
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 *
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 * Libav is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * Libav is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with Libav; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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#ifndef PCM_TABLEGEN_H
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#define PCM_TABLEGEN_H
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#include <stdint.h>
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#include "libavutil/attributes.h"
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/* from g711.c by SUN microsystems (unrestricted use) */
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#define         SIGN_BIT        (0x80)      /* Sign bit for a A-law byte. */
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#define         QUANT_MASK      (0xf)       /* Quantization field mask. */
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#define         NSEGS           (8)         /* Number of A-law segments. */
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#define         SEG_SHIFT       (4)         /* Left shift for segment number. */
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#define         SEG_MASK        (0x70)      /* Segment field mask. */
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#define         BIAS            (0x84)      /* Bias for linear code. */
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/*
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 * alaw2linear() - Convert an A-law value to 16-bit linear PCM
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 *
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 */
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static av_cold int alaw2linear(unsigned char a_val)
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{
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        int t;
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        int seg;
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        a_val ^= 0x55;
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        t = a_val & QUANT_MASK;
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        seg = ((unsigned)a_val & SEG_MASK) >> SEG_SHIFT;
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        if(seg) t= (t + t + 1 + 32) << (seg + 2);
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        else    t= (t + t + 1     ) << 3;
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        return (a_val & SIGN_BIT) ? t : -t;
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}
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static av_cold int ulaw2linear(unsigned char u_val)
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{
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        int t;
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        /* Complement to obtain normal u-law value. */
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        u_val = ~u_val;
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        /*
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         * Extract and bias the quantization bits. Then
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         * shift up by the segment number and subtract out the bias.
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         */
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        t = ((u_val & QUANT_MASK) << 3) + BIAS;
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        t <<= ((unsigned)u_val & SEG_MASK) >> SEG_SHIFT;
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        return (u_val & SIGN_BIT) ? (BIAS - t) : (t - BIAS);
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}
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#if CONFIG_HARDCODED_TABLES
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#define pcm_alaw_tableinit()
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#define pcm_ulaw_tableinit()
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#include "libavcodec/pcm_tables.h"
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#else
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/* 16384 entries per table */
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static uint8_t linear_to_alaw[16384];
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static uint8_t linear_to_ulaw[16384];
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static av_cold void build_xlaw_table(uint8_t *linear_to_xlaw,
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                             int (*xlaw2linear)(unsigned char),
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                             int mask)
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{
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    int i, j, v, v1, v2;
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    j = 0;
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    for(i=0;i<128;i++) {
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        if (i != 127) {
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            v1 = xlaw2linear(i ^ mask);
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            v2 = xlaw2linear((i + 1) ^ mask);
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            v = (v1 + v2 + 4) >> 3;
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        } else {
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            v = 8192;
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        }
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        for(;j<v;j++) {
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            linear_to_xlaw[8192 + j] = (i ^ mask);
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            if (j > 0)
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                linear_to_xlaw[8192 - j] = (i ^ (mask ^ 0x80));
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        }
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    }
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    linear_to_xlaw[0] = linear_to_xlaw[1];
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}
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static void pcm_alaw_tableinit(void)
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{
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    build_xlaw_table(linear_to_alaw, alaw2linear, 0xd5);
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}
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static void pcm_ulaw_tableinit(void)
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{
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    build_xlaw_table(linear_to_ulaw, ulaw2linear, 0xff);
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}
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#endif /* CONFIG_HARDCODED_TABLES */
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#endif /* PCM_TABLEGEN_H */