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layer1.c
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layer1.c
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/*
layer1.c: the layer 1 decoder
copyright 1995-2009 by the mpg123 project - free software under the terms of the LGPL 2.1
see COPYING and AUTHORS files in distribution or http://mpg123.org
initially written by Michael Hipp
may have a few bugs after last optimization ...
*/
#include "mpg123lib_intern.h"
#include "getbits.h"
#include "debug.h"
/*
Allocation value is not allowed to be 15. Initially, libmad showed me the
error that mpg123 used to ignore. Then, I found a quote on that in
Shlien, S. (1994): Guide to MPEG-1 Audio Standard.
IEEE Transactions on Broadcasting 40, 4
"To avoid conflicts with the synchronization code, code '1111' is defined
to be illegal."
*/
static int check_balloc(mpg123_handle *fr, unsigned int *balloc, unsigned int *end)
{
unsigned int *ba;
for(ba=balloc; ba != end; ++ba)
if(*ba == 15)
{
if(NOQUIET) error("Illegal bit allocation value.");
return -1;
}
return 0;
}
static int I_step_one(unsigned int balloc[], unsigned int scale_index[2][SBLIMIT],mpg123_handle *fr)
{
unsigned int *ba=balloc;
unsigned int *sca = (unsigned int *) scale_index;
if(fr->stereo == 2)
{
int i;
int jsbound = fr->jsbound;
for(i=0;i<jsbound;i++)
{
*ba++ = getbits(fr, 4);
*ba++ = getbits(fr, 4);
}
for(i=jsbound;i<SBLIMIT;i++) *ba++ = getbits(fr, 4);
if(check_balloc(fr, balloc, ba)) return -1;
ba = balloc;
for(i=0;i<jsbound;i++)
{
if ((*ba++))
*sca++ = getbits(fr, 6);
if ((*ba++))
*sca++ = getbits(fr, 6);
}
for (i=jsbound;i<SBLIMIT;i++)
if((*ba++))
{
*sca++ = getbits(fr, 6);
*sca++ = getbits(fr, 6);
}
}
else
{
int i;
for(i=0;i<SBLIMIT;i++) *ba++ = getbits(fr, 4);
if(check_balloc(fr, balloc, ba)) return -1;
ba = balloc;
for (i=0;i<SBLIMIT;i++)
if ((*ba++))
*sca++ = getbits(fr, 6);
}
return 0;
}
/* Something sane in place of undefined (-1)<<n. Well, not really. */
#define MINUS_SHIFT(n) ( (int)(((unsigned int)-1)<<(n)) )
static void I_step_two(real fraction[2][SBLIMIT],unsigned int balloc[2*SBLIMIT], unsigned int scale_index[2][SBLIMIT],mpg123_handle *fr)
{
int i,n;
int smpb[2*SBLIMIT]; /* values: 0-65535 */
int *sample;
register unsigned int *ba;
register unsigned int *sca = (unsigned int *) scale_index;
if(fr->stereo == 2)
{
int jsbound = fr->jsbound;
register real *f0 = fraction[0];
register real *f1 = fraction[1];
ba = balloc;
for(sample=smpb,i=0;i<jsbound;i++)
{
if((n = *ba++)) *sample++ = getbits(fr, n+1);
if((n = *ba++)) *sample++ = getbits(fr, n+1);
}
for(i=jsbound;i<SBLIMIT;i++)
if((n = *ba++))
*sample++ = getbits(fr, n+1);
ba = balloc;
for(sample=smpb,i=0;i<jsbound;i++)
{
if((n=*ba++))
*f0++ = REAL_MUL_SCALE_LAYER12(DOUBLE_TO_REAL_15(MINUS_SHIFT(n) + (*sample++) + 1), fr->muls[n+1][*sca++]);
else *f0++ = DOUBLE_TO_REAL(0.0);
if((n=*ba++))
*f1++ = REAL_MUL_SCALE_LAYER12(DOUBLE_TO_REAL_15(MINUS_SHIFT(n) + (*sample++) + 1), fr->muls[n+1][*sca++]);
else *f1++ = DOUBLE_TO_REAL(0.0);
}
for(i=jsbound;i<SBLIMIT;i++)
{
if((n=*ba++))
{
real samp = DOUBLE_TO_REAL_15(MINUS_SHIFT(n) + (*sample++) + 1);
*f0++ = REAL_MUL_SCALE_LAYER12(samp, fr->muls[n+1][*sca++]);
*f1++ = REAL_MUL_SCALE_LAYER12(samp, fr->muls[n+1][*sca++]);
}
else *f0++ = *f1++ = DOUBLE_TO_REAL(0.0);
}
for(i=fr->down_sample_sblimit;i<32;i++)
fraction[0][i] = fraction[1][i] = 0.0;
}
else
{
register real *f0 = fraction[0];
ba = balloc;
for(sample=smpb,i=0;i<SBLIMIT;i++)
if ((n = *ba++))
*sample++ = getbits(fr, n+1);
ba = balloc;
for(sample=smpb,i=0;i<SBLIMIT;i++)
{
if((n=*ba++))
*f0++ = REAL_MUL_SCALE_LAYER12(DOUBLE_TO_REAL_15(MINUS_SHIFT(n) + (*sample++) + 1), fr->muls[n+1][*sca++]);
else *f0++ = DOUBLE_TO_REAL(0.0);
}
for(i=fr->down_sample_sblimit;i<32;i++)
fraction[0][i] = DOUBLE_TO_REAL(0.0);
}
}
int do_layer1(mpg123_handle *fr)
{
int clip=0;
int i,stereo = fr->stereo;
unsigned int balloc[2*SBLIMIT];
unsigned int scale_index[2][SBLIMIT];
real (*fraction)[SBLIMIT] = fr->layer1.fraction; /* fraction[2][SBLIMIT] */
int single = fr->single;
fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ? (fr->mode_ext<<2)+4 : 32;
if(stereo == 1 || single == SINGLE_MIX) /* I don't see mixing handled here */
single = SINGLE_LEFT;
if(I_step_one(balloc,scale_index,fr))
{
if(NOQUIET) error("Aborting layer I decoding after step one.\n");
return clip;
}
for(i=0;i<SCALE_BLOCK;i++)
{
I_step_two(fraction,balloc,scale_index,fr);
if(single != SINGLE_STEREO)
clip += (fr->synth_mono)(fraction[single], fr);
else
clip += (fr->synth_stereo)(fraction[0], fraction[1], fr);
}
return clip;
}