mirror of
https://github.com/RetroDECK/Supermodel.git
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409 lines
9.3 KiB
C++
409 lines
9.3 KiB
C++
/**
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** Supermodel
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** A Sega Model 3 Arcade Emulator.
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** Copyright 2011 Bart Trzynadlowski, Nik Henson
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**
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** This file is part of Supermodel.
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**
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** Supermodel is free software: you can redistribute it and/or modify it under
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** the terms of the GNU General Public License as published by the Free
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** Software Foundation, either version 3 of the License, or (at your option)
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** any later version.
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**
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** Supermodel is distributed in the hope that it will be useful, but WITHOUT
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** ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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** FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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** more details.
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**
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** You should have received a copy of the GNU General Public License along
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** with Supermodel. If not, see <http://www.gnu.org/licenses/>.
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**/
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/*
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* getbits.cpp
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*
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* Amp library internal module.
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*/
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/* this file is a part of amp software, (C) tomislav uzelac 1996,1997
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*/
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/* getbits.c bit level routines, input buffer
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*
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* Created by: tomislav uzelac Apr 1996
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* better synchronization, tomislav uzelac, Apr 23 1997
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "amp.h"
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#include "audio.h"
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#include "formats.h"
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#include "rtbuf.h"
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#define GETBITS
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#include "getbits.h"
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static const char *fstart, *lstart;
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static int offset, end, eof, lend;
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void MPEG_GetPlayPosition(int *playOffset, int *endOffset)
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{
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if (in_file)
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*playOffset = ftell(in_file);
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else
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*playOffset = offset;
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*endOffset = end;
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}
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void MPEG_SetPlayPosition(int playOffset, int endOffset)
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{
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offset = playOffset;
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end = endOffset;
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}
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void m1setfile(const char *mstart, int mend)
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{
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fstart = mstart;
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offset = 0;
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eof = 0;
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end = mend;
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lstart = NULL;
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}
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void MPEG_SetLoop(const char *loop, int loopend)
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{
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lstart = loop;
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lend = loopend;
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}
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int m1fread(unsigned char *buf, int size1, int size2, void *f)
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{
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int total = size1 * size2;
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if (in_file) return fread(buf, size1, size2, (FILE *) f);
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//printf("fstart=%X, total=%X, offset=%X, end=%X\n", fstart, total, offset, end);
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// if past EOF
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if ((total + offset) >= end)
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{
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if (lstart == NULL)
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{
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total = end - offset;
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eof = 1;
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}
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else
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{
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// if past the end, do the xfer in 2 pieces
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if ((total + offset) > end)
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{
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memcpy(buf, fstart + offset, end-offset);
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buf += (end-offset);
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total -= (end-offset);
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}
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fstart = lstart;
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offset = 0;
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end = lend;
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}
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}
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memcpy(buf, fstart + offset, total);
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offset += total;
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return total;
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}
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int m1feof(void *f)
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{
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if (in_file) return feof((FILE *)f);
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return eof;
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}
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int m1fseek(void *f, int offs, int whence)
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{
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if (in_file) return fseek((FILE *) f, offs, whence);
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switch (whence)
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{
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case SEEK_CUR:
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if ((offset + offs) < 0)
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{
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offset = 0;
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eof = 0;
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return -1;
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}
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if ((offset + offs) > end)
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{
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offset = end;
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eof = 1;
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return end;
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}
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offset += offs;
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eof = 0;
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break;
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}
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return 0;
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}
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/*
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* buffer and bit manipulation functions ***************************************
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*/
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static inline int _fillbfr(unsigned int size)
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{
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_bptr=0;
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return get_input(_buffer, size);
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}
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static inline int readsync()
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{
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_bptr=0;
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_buffer[0]=_buffer[1];
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_buffer[1]=_buffer[2];
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_buffer[2]=_buffer[3];
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return get_input(&_buffer[3],1);
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}
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static inline unsigned int _getbits(int n)
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{
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unsigned int pos,ret_value;
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pos = _bptr >> 3;
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ret_value = _buffer[pos] << 24 |
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_buffer[pos+1] << 16 |
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_buffer[pos+2] << 8 |
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_buffer[pos+3];
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ret_value <<= _bptr & 7;
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ret_value >>= 32 - n;
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_bptr += n;
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return ret_value;
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}
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int fillbfr(unsigned int advance)
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{
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int overflow,retval;
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retval=get_input(&buffer[append], advance);
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if ( append + advance >= BUFFER_SIZE ) {
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overflow = append + advance - BUFFER_SIZE;
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memcpy (buffer,&buffer[BUFFER_SIZE], overflow);
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if (overflow < 4) memcpy(&buffer[BUFFER_SIZE],buffer,4);
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append = overflow;
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} else {
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if (append==0) memcpy(&buffer[BUFFER_SIZE],buffer,4);
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append+=advance;
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}
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return retval;
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}
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unsigned int getbits(int n)
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{
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if (n) {
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unsigned int pos,ret_value;
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pos = data >> 3;
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ret_value = buffer[pos] << 24 |
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buffer[pos+1] << 16 |
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buffer[pos+2] << 8 |
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buffer[pos+3];
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ret_value <<= data & 7;
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ret_value >>= 32 - n;
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data += n;
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data &= (8*BUFFER_SIZE)-1;
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return ret_value;
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} else
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return 0;
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}
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/*
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* header and side info parsing stuff ******************************************
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*/
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static inline void parse_header(struct AUDIO_HEADER *header)
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{
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header->ID=_getbits(1);
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header->layer=_getbits(2);
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header->protection_bit=_getbits(1);
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header->bitrate_index=_getbits(4);
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header->sampling_frequency=_getbits(2);
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header->padding_bit=_getbits(1);
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header->private_bit=_getbits(1);
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header->mode=_getbits(2);
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header->mode_extension=_getbits(2);
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if (!header->mode) header->mode_extension=0;
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header->copyright=_getbits(1);
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header->original=_getbits(1);
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header->emphasis=_getbits(2);
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}
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static inline int header_sanity_check(struct AUDIO_HEADER *header)
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{
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if ( header->layer==0 ||
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header->bitrate_index==15 ||
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header->sampling_frequency==3) return -1;
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/* an additional check to make shure that stuffing never gets mistaken
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* for a syncword. This rules out some legal layer1 streams, but who
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* cares about layer1 anyway :-). I must get this right sometime.
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*/
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if ( header->ID==1 && header->layer==3 && header->protection_bit==1) return -1;
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return 0;
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}
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int gethdr(struct AUDIO_HEADER *header)
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{
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int s,retval;
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struct AUDIO_HEADER tmp;
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/* TODO: add a simple byte counter to check only first, say, 1024
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* bytes for a new header and then return GETHDR_SYN
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*/
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if ((retval=_fillbfr(4))!=0) return retval;
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for(;;) {
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while ((s=_getbits(12)) != 0xfff) {
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if (s==0xffe) {
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parse_header(&tmp);
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if (header_sanity_check(&tmp)==0) return GETHDR_NS;
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}
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if ((retval=readsync())!=0) return retval;
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}
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parse_header(&tmp);
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if (header_sanity_check(&tmp)!=0) {
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if ((retval=readsync())!=0) return retval;
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} else break;
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}
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if (tmp.layer==3) return GETHDR_FL1;
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/* if (tmp.layer==2) return GETHDR_FL2; */
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if (tmp.bitrate_index==0) return GETHDR_FF;
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//printf("layer: %d\n", tmp.layer);
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//printf("sampling frequency: %d\n", tmp.sampling_frequency);
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memcpy(header,&tmp,sizeof(tmp));
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return 0;
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}
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/* dummy function, to get crc out of the way
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*/
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void getcrc()
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{
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_fillbfr(2);
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_getbits(16);
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}
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/* sizes of side_info:
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* MPEG1 1ch 17 2ch 32
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* MPEG2 1ch 9 2ch 17
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*/
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void getinfo(struct AUDIO_HEADER *header,struct SIDE_INFO *info)
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{
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int gr,ch,scfsi_band,region,window;
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int nch;
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if (header->mode==3) {
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nch=1;
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if (header->ID) {
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_fillbfr(17);
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info->main_data_begin=_getbits(9);
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_getbits(5);
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} else {
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_fillbfr(9);
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info->main_data_begin=_getbits(8);
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_getbits(1);
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}
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} else {
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nch=2;
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if (header->ID) {
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_fillbfr(32);
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info->main_data_begin=_getbits(9);
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_getbits(3);
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} else {
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_fillbfr(17);
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info->main_data_begin=_getbits(8);
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_getbits(2);
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}
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}
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if (header->ID) for (ch=0;ch<nch;ch++)
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for (scfsi_band=0;scfsi_band<4;scfsi_band++)
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info->scfsi[ch][scfsi_band]=_getbits(1);
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for (gr=0;gr<(header->ID ? 2:1);gr++)
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for (ch=0;ch<nch;ch++) {
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info->part2_3_length[gr][ch]=_getbits(12);
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info->big_values[gr][ch]=_getbits(9);
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info->global_gain[gr][ch]=_getbits(8);
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if (header->ID) info->scalefac_compress[gr][ch]=_getbits(4);
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else info->scalefac_compress[gr][ch]=_getbits(9);
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info->window_switching_flag[gr][ch]=_getbits(1);
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if (info->window_switching_flag[gr][ch]) {
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info->block_type[gr][ch]=_getbits(2);
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info->mixed_block_flag[gr][ch]=_getbits(1);
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for (region=0;region<2;region++)
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info->table_select[gr][ch][region]=_getbits(5);
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info->table_select[gr][ch][2]=0;
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for (window=0;window<3;window++)
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info->subblock_gain[gr][ch][window]=_getbits(3);
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} else {
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for (region=0;region<3;region++)
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info->table_select[gr][ch][region]=_getbits(5);
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info->region0_count[gr][ch]=_getbits(4);
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info->region1_count[gr][ch]=_getbits(3);
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info->block_type[gr][ch]=0;
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}
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if (header->ID) info->preflag[gr][ch]=_getbits(1);
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info->scalefac_scale[gr][ch]=_getbits(1);
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info->count1table_select[gr][ch]=_getbits(1);
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}
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return;
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}
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int dummy_getinfo(int n)
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{
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n-=4;
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if ( m1fseek(in_file,n,SEEK_CUR) != 0)
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{
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if (m1feof(in_file)) return GETHDR_EOF;
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else return GETHDR_ERR;
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}
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return 0;
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}
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int rewind_stream(int nbytes)
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{
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nbytes+=5;
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if (m1fseek(in_file, -nbytes, SEEK_CUR) != 0) {
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/* what if we need to be at the very beginning? */
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nbytes--;
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if (m1fseek(in_file, -nbytes, SEEK_CUR) != 0) return GETHDR_ERR;
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}
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return 0;
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}
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static inline int get_input(unsigned char* bp, unsigned int size)
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{
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#ifdef LINUX_REALTIME
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return prefetch_get_input(bp,size);
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#else /* LINUX_REALTIME */
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if ( m1fread( bp , 1, size, in_file) != size)
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{
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if (m1feof(in_file)) return GETHDR_EOF;
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else return GETHDR_ERR;
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}
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return 0;
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#endif /* LINUX_REALTIME */
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}
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