lpc.c File Reference

#include <stdio.h>
#include <assert.h>
#include "private.h"
#include "gsm.h"
#include "proto.h"

Include dependency graph for lpc.c:

Go to the source code of this file.

Macros
#define	NEXTI   sl = *++sp
#define	SCALE(n)
#define	STEP(A, B, MAC, MIC)
#define	STEP(k)   L_ACF[k] += ((longword)sl * sp[ -(k) ]);

Functions
static void Quantization_and_coding	P1 ((LAR), register word *LAR)
static void Transformation_to_Log_Area_Ratios	P1 ((r), register word *r)
static void Reflection_coefficients	P2 ((L_ACF, r), longword *L_ACF, register word *r)
static void Autocorrelation	P2 ((s, L_ACF), word *s, longword *L_ACF)
void Gsm_LPC_Analysis	P3 ((S, s, LARc), struct gsm_state *S, word *s, word *LARc)

Macro Definition Documentation

NEXTI

#define NEXTI   sl = *++sp

SCALE

#define SCALE

(

n

)

Value:

    case n: for (k = 0; k <= 159; k++) \
            s[k] = (word)GSM_MULT_R( s[k], 16384 >> (n-1) );\
        break;

STEP [1/2]

#define STEP	(		A,
			B,
			MAC,
			MIC
	)

STEP [2/2]

#define STEP

(

k

)

L_ACF[k] += ((longword)sl * sp[ -(k) ]);

Function Documentation

P1() [1/2]

static void Quantization_and_coding P1 ( (LAR)  , register word *  LAR  )

static

Definition at line 319 of file lpc.c.

{
    register word   temp;
 
 
    /*  This procedure needs four tables; the following equations
     *  give the optimum scaling for the constants:
     *
     *  A[0..7] = integer( real_A[0..7] * 1024 )
     *  B[0..7] = integer( real_B[0..7] *  512 )
     *  MAC[0..7] = maximum of the LARc[0..7]
     *  MIC[0..7] = minimum of the LARc[0..7]
     */
 
#   undef STEP
#   define  STEP( A, B, MAC, MIC )      \
        temp = (word)GSM_MULT( A,   *LAR ); \
        temp = GSM_ADD(  temp,   B );   \
        temp = GSM_ADD(  temp, 256 );   \
        temp = (word)SASR(     temp,   9 ); \
        *LAR  =  temp>MAC ? MAC - MIC : (temp<MIC ? 0 : temp - MIC); \
        LAR++;
 
    STEP(  20480,     0,  31, -32 );
    STEP(  20480,     0,  31, -32 );
    STEP(  20480,  2048,  15, -16 );
    STEP(  20480, -2560,  15, -16 );
 
    STEP(  13964,    94,   7,  -8 );
    STEP(  15360, -1792,   7,  -8 );
    STEP(   8534,  -341,   3,  -4 );
    STEP(   9036, -1144,   3,  -4 );
 
#   undef   STEP
}

References STEP.

P1() [2/2]

static void Transformation_to_Log_Area_Ratios P1 ( (r)  , register word *  r  )

static

Definition at line 278 of file lpc.c.

{
    register word   temp;
    register int    i;
 
 
    /* Computation of the LAR[0..7] from the r[0..7]
     */
    for (i = 1; i <= 8; i++, r++) {
 
        temp = *r;
        temp = GSM_ABS(temp);
        assert(temp >= 0);
 
        if (temp < 22118) {
            temp >>= 1;
        } else if (temp < 31130) {
            assert( temp >= 11059 );
            temp -= 11059;
        } else {
            assert( temp >= 26112 );
            temp -= 26112;
            temp <<= 2;
        }
 
        *r = *r < 0 ? -temp : temp;
        assert( *r != MIN_WORD );
    }
}

References GSM_ABS, and MIN_WORD.

P2() [1/2]

static void Reflection_coefficients P2 ( (L_ACF, r)  , longword *  L_ACF, register word *  r  )

static

Definition at line 210 of file lpc.c.

{
    register int    i, m, n;
    register word   temp;
    word        ACF[9]; /* 0..8 */
    word        P[  9]; /* 0..8 */
    word        K[  9]; /* 2..8 */
 
    /*  Schur recursion with 16 bits arithmetic.
     */
 
    if (L_ACF[0] == 0) {
        for (i = 8; i--; *r++ = 0) ;
        return;
    }
 
    assert( L_ACF[0] != 0 );
    temp = gsm_norm( L_ACF[0] );
 
    assert(temp >= 0 && temp < 32);
 
    /* ? overflow ? */
    for (i = 0; i <= 8; i++) ACF[i] = (word)SASR( L_ACF[i] << temp, 16 );
 
    /*   Initialize array P[..] and K[..] for the recursion.
     */
 
    for (i = 1; i <= 7; i++) K[ i ] = ACF[ i ];
    for (i = 0; i <= 8; i++) P[ i ] = ACF[ i ];
 
    /*   Compute reflection coefficients
     */
    for (n = 1; n <= 8; n++, r++) {
 
        temp = P[1];
        temp = GSM_ABS(temp);
        if (P[0] < temp) {
            for (i = n; i <= 8; i++) *r++ = 0;
            return;
        }
 
        *r = gsm_div( temp, P[0] );
 
        assert(*r >= 0);
        if (P[1] > 0) *r = -*r;     /* r[n] = sub(0, r[n]) */
        assert (*r != MIN_WORD);
        if (n == 8) return;
 
        /*  Schur recursion
         */
        temp = (word)GSM_MULT_R( P[1], *r );
        P[0] = GSM_ADD( P[0], temp );
 
        for (m = 1; m <= 8 - n; m++) {
            temp     = (word)GSM_MULT_R( K[ m   ],    *r );
            P[m]     = GSM_ADD(    P[ m+1 ],  temp );
 
            temp     = (word)GSM_MULT_R( P[ m+1 ],    *r );
            K[m]     = GSM_ADD(    K[ m   ],  temp );
        }
    }
}

References GSM_ABS, GSM_ADD(), GSM_MULT_R, MIN_WORD, P, and SASR.

P2() [2/2]

static void Autocorrelation P2 ( (s, L_ACF)  , word *  s, longword *  L_ACF  )

static

Definition at line 30 of file lpc.c.

{
#ifndef K6OPT
    register int    k, i;
    word temp;
#endif
 
    word        smax, scalauto;
 
#ifdef  USE_FLOAT_MUL
    float       float_s[160];
#endif
 
    /*  Dynamic scaling of the array  s[0..159]
     */
 
    /*  Search for the maximum.
     */
#ifndef K6OPT
    smax = 0;
    for (k = 0; k <= 159; k++) {
        temp = GSM_ABS( s[k] );
        if (temp > smax) smax = temp;
    }
#else
    {
        longword lmax;
        lmax = k6maxmin(s,160,NULL);
        smax = (lmax > MAX_WORD) ? MAX_WORD : lmax;
    }
#endif
    /*  Computation of the scaling factor.
     */
    if (smax == 0) scalauto = 0;
    else {
        assert(smax > 0);
        scalauto = 4 - gsm_norm( (longword)smax << 16 );/* sub(4,..) */
    }
 
    /*  Scaling of the array s[0...159]
     */
 
    if (scalauto > 0) {
#   ifndef K6OPT
 
# ifdef USE_FLOAT_MUL
#   define SCALE(n) \
    case n: for (k = 0; k <= 159; k++) \
            float_s[k] = (float)    \
                (s[k] = GSM_MULT_R(s[k], 16384 >> (n-1)));\
        break;
# else
#   define SCALE(n) \
    case n: for (k = 0; k <= 159; k++) \
            s[k] = (word)GSM_MULT_R( s[k], 16384 >> (n-1) );\
        break;
# endif /* USE_FLOAT_MUL */
 
        switch (scalauto) {
        SCALE(1)
        SCALE(2)
        SCALE(3)
        SCALE(4)
        }
# undef SCALE
 
#   else /* K6OPT */
        k6vsraw(s,160,scalauto);
#   endif
    }
# ifdef USE_FLOAT_MUL
    else for (k = 0; k <= 159; k++) float_s[k] = (float) s[k];
# endif
 
    /*  Compute the L_ACF[..].
     */
#ifndef K6OPT
    {
# ifdef USE_FLOAT_MUL
        register float * sp = float_s;
        register float   sl = *sp;
 
#       define STEP(k)   L_ACF[k] += (longword)(sl * sp[ -(k) ]);
# else
        word  * sp = s;
        word    sl = *sp;
 
#       define STEP(k)   L_ACF[k] += ((longword)sl * sp[ -(k) ]);
# endif
 
#   define NEXTI     sl = *++sp
 
 
    for (k = 9; k--; L_ACF[k] = 0) ;
 
    STEP (0);
    NEXTI;
    STEP(0); STEP(1);
    NEXTI;
    STEP(0); STEP(1); STEP(2);
    NEXTI;
    STEP(0); STEP(1); STEP(2); STEP(3);
    NEXTI;
    STEP(0); STEP(1); STEP(2); STEP(3); STEP(4);
    NEXTI;
    STEP(0); STEP(1); STEP(2); STEP(3); STEP(4); STEP(5);
    NEXTI;
    STEP(0); STEP(1); STEP(2); STEP(3); STEP(4); STEP(5); STEP(6);
    NEXTI;
    STEP(0); STEP(1); STEP(2); STEP(3); STEP(4); STEP(5); STEP(6); STEP(7);
 
    for (i = 8; i <= 159; i++) {
 
        NEXTI;
 
        STEP(0);
        STEP(1); STEP(2); STEP(3); STEP(4);
        STEP(5); STEP(6); STEP(7); STEP(8);
    }
 
    for (k = 9; k--; L_ACF[k] <<= 1) ;
 
    }
 
#else
    {
        int k;
        for (k=0; k<9; k++) {
            L_ACF[k] = 2*k6iprod(s,s+k,160-k);
        }
    }
#endif
    /*   Rescaling of the array s[0..159]
     */
    if (scalauto > 0) {
        assert(scalauto <= 4);
#ifndef K6OPT
        for (k = 160; k--; *s++ <<= scalauto) ;
#   else /* K6OPT */
        k6vsllw(s,160,scalauto);
#   endif
    }
}

References GSM_ABS, MAX_WORD, NEXTI, NULL, SCALE, and STEP.

P3()

void Gsm_LPC_Analysis P3	(	(S, s, LARc)	,
		struct gsm_state *	S,
		word *	s,
		word *	LARc
	)

Definition at line 357 of file lpc.c.

{
    longword    L_ACF[9];
 
#if defined(USE_FLOAT_MUL) && defined(FAST)
    if (S->fast) Fast_Autocorrelation (s,     L_ACF );
    else
#endif
    Autocorrelation           (s,     L_ACF );
    Reflection_coefficients       (L_ACF, LARc  );
    Transformation_to_Log_Area_Ratios (LARc);
    Quantization_and_coding       (LARc);
}

References LARc, and S.