/*

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;

}