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Supermodel/Src/Sound/MPEG/getbits.cpp

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