shithub: opus

ref: dac77d134471a02a4d5b8260650882b2a7517a83
dir: /silk/silk_Inlines.h/

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/*! \file silk_Inlines.h
 *  \brief silk_Inlines.h defines inline signal processing functions.
 */

#ifndef _SILK_FIX_INLINES_H_
#define _SILK_FIX_INLINES_H_

#ifdef  __cplusplus
extern "C"
{
#endif

/* count leading zeros of opus_int64 */
SKP_INLINE opus_int32 silk_CLZ64(opus_int64 in)
{
    opus_int32 in_upper;

    in_upper = (opus_int32)SKP_RSHIFT64(in, 32);
    if (in_upper == 0) {
        /* Search in the lower 32 bits */
        return 32 + silk_CLZ32( (opus_int32) in );
    } else {
        /* Search in the upper 32 bits */
        return silk_CLZ32( in_upper );
    }
}

/* get number of leading zeros and fractional part (the bits right after the leading one */
SKP_INLINE void silk_CLZ_FRAC(opus_int32 in,            /* I: input */
                                    opus_int32 *lz,           /* O: number of leading zeros */
                                    opus_int32 *frac_Q7)      /* O: the 7 bits right after the leading one */
{
    opus_int32 lzeros = silk_CLZ32(in);

    * lz = lzeros;
    * frac_Q7 = silk_ROR32(in, 24 - lzeros) & 0x7f;
}

/* Approximation of square root                                          */
/* Accuracy: < +/- 10%  for output values > 15                           */
/*           < +/- 2.5% for output values > 120                          */
SKP_INLINE opus_int32 silk_SQRT_APPROX(opus_int32 x)
{
    opus_int32 y, lz, frac_Q7;

    if( x <= 0 ) {
        return 0;
    }

    silk_CLZ_FRAC(x, &lz, &frac_Q7);

    if( lz & 1 ) {
        y = 32768;
    } else {
        y = 46214;        /* 46214 = sqrt(2) * 32768 */
    }

    /* get scaling right */
    y >>= SKP_RSHIFT(lz, 1);

    /* increment using fractional part of input */
    y = SKP_SMLAWB(y, y, SKP_SMULBB(213, frac_Q7));

    return y;
}

/* Divide two int32 values and return result as int32 in a given Q-domain */
SKP_INLINE opus_int32 silk_DIV32_varQ(    /* O    returns a good approximation of "(a32 << Qres) / b32" */
    const opus_int32     a32,            /* I    numerator (Q0)                  */
    const opus_int32     b32,            /* I    denominator (Q0)                */
    const opus_int       Qres            /* I    Q-domain of result (>= 0)       */
)
{
    opus_int   a_headrm, b_headrm, lshift;
    opus_int32 b32_inv, a32_nrm, b32_nrm, result;

    SKP_assert( b32 != 0 );
    SKP_assert( Qres >= 0 );

    /* Compute number of bits head room and normalize inputs */
    a_headrm = silk_CLZ32( SKP_abs(a32) ) - 1;
    a32_nrm = SKP_LSHIFT(a32, a_headrm);                                    /* Q: a_headrm                    */
    b_headrm = silk_CLZ32( SKP_abs(b32) ) - 1;
    b32_nrm = SKP_LSHIFT(b32, b_headrm);                                    /* Q: b_headrm                    */

    /* Inverse of b32, with 14 bits of precision */
    b32_inv = SKP_DIV32_16( SKP_int32_MAX >> 2, SKP_RSHIFT(b32_nrm, 16) );  /* Q: 29 + 16 - b_headrm        */

    /* First approximation */
    result = SKP_SMULWB(a32_nrm, b32_inv);                                  /* Q: 29 + a_headrm - b_headrm    */

    /* Compute residual by subtracting product of denominator and first approximation */
    a32_nrm -= SKP_LSHIFT_ovflw( SKP_SMMUL(b32_nrm, result), 3 );           /* Q: a_headrm                    */

    /* Refinement */
    result = SKP_SMLAWB(result, a32_nrm, b32_inv);                          /* Q: 29 + a_headrm - b_headrm    */

    /* Convert to Qres domain */
    lshift = 29 + a_headrm - b_headrm - Qres;
    if( lshift < 0 ) {
        return SKP_LSHIFT_SAT32(result, -lshift);
    } else {
        if( lshift < 32){
            return SKP_RSHIFT(result, lshift);
        } else {
            /* Avoid undefined result */
            return 0;
        }
    }
}

/* Invert int32 value and return result as int32 in a given Q-domain */
SKP_INLINE opus_int32 silk_INVERSE32_varQ(    /* O    returns a good approximation of "(1 << Qres) / b32" */
    const opus_int32     b32,                /* I    denominator (Q0)                */
    const opus_int       Qres                /* I    Q-domain of result (> 0)        */
)
{
    opus_int   b_headrm, lshift;
    opus_int32 b32_inv, b32_nrm, err_Q32, result;

    SKP_assert( b32 != 0 );
    SKP_assert( Qres > 0 );

    /* Compute number of bits head room and normalize input */
    b_headrm = silk_CLZ32( SKP_abs(b32) ) - 1;
    b32_nrm = SKP_LSHIFT(b32, b_headrm);                                    /* Q: b_headrm                */

    /* Inverse of b32, with 14 bits of precision */
    b32_inv = SKP_DIV32_16( SKP_int32_MAX >> 2, SKP_RSHIFT(b32_nrm, 16) );  /* Q: 29 + 16 - b_headrm    */

    /* First approximation */
    result = SKP_LSHIFT(b32_inv, 16);                                       /* Q: 61 - b_headrm            */

    /* Compute residual by subtracting product of denominator and first approximation from one */
    err_Q32 = SKP_LSHIFT_ovflw( -SKP_SMULWB(b32_nrm, b32_inv), 3 );         /* Q32                        */

    /* Refinement */
    result = SKP_SMLAWW(result, err_Q32, b32_inv);                          /* Q: 61 - b_headrm            */

    /* Convert to Qres domain */
    lshift = 61 - b_headrm - Qres;
    if( lshift <= 0 ) {
        return SKP_LSHIFT_SAT32(result, -lshift);
    } else {
        if( lshift < 32){
            return SKP_RSHIFT(result, lshift);
        }else{
            /* Avoid undefined result */
            return 0;
        }
    }
}

#ifdef  __cplusplus
}
#endif

#endif //_SILK_FIX_INLINES_H_