mirror of https://git.ffmpeg.org/ffmpeg.git
120 lines
3.4 KiB
C
120 lines
3.4 KiB
C
/*
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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 FFmpeg.
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*
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* FFmpeg 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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* FFmpeg 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 FFmpeg; 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 */
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