media/libopus/silk/Inlines.h

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  27
  28 /*! \file silk_Inlines.h
  29  *  \brief silk_Inlines.h defines OPUS_INLINE signal processing functions.
  30  */
  31
  32 #ifndef SILK_FIX_INLINES_H
  33 #define SILK_FIX_INLINES_H
  34
  35 #ifdef  __cplusplus
  36 extern "C"
  37 {
  38 #endif
  39
  40 /* count leading zeros of opus_int64 */
  41 static OPUS_INLINE opus_int32 silk_CLZ64( opus_int64 in )
  42 {
  43     opus_int32 in_upper;
  44
  45     in_upper = (opus_int32)silk_RSHIFT64(in, 32);
  46     if (in_upper == 0) {
  47         /* Search in the lower 32 bits */
  48         return 32 + silk_CLZ32( (opus_int32) in );
  49     } else {
  50         /* Search in the upper 32 bits */
  51         return silk_CLZ32( in_upper );
  52     }
  53 }
  54
  55 /* get number of leading zeros and fractional part (the bits right after the leading one */
  56 static OPUS_INLINE void silk_CLZ_FRAC(
  57     opus_int32 in,            /* I  input                               */
  58     opus_int32 *lz,           /* O  number of leading zeros             */
  59     opus_int32 *frac_Q7       /* O  the 7 bits right after the leading one */
  60 )
  61 {
  62     opus_int32 lzeros = silk_CLZ32(in);
  63
  64     * lz = lzeros;
  65     * frac_Q7 = silk_ROR32(in, 24 - lzeros) & 0x7f;
  66 }
  67
  68 /* Approximation of square root                                          */
  69 /* Accuracy: < +/- 10%  for output values > 15                           */
  70 /*           < +/- 2.5% for output values > 120                          */
  71 static OPUS_INLINE opus_int32 silk_SQRT_APPROX( opus_int32 x )
  72 {
  73     opus_int32 y, lz, frac_Q7;
  74
  75     if( x <= 0 ) {
  76         return 0;
  77     }
  78
  79     silk_CLZ_FRAC(x, &lz, &frac_Q7);
  80
  81     if( lz & 1 ) {
  82         y = 32768;
  83     } else {
  84         y = 46214;        /* 46214 = sqrt(2) * 32768 */
  85     }
  86
  87     /* get scaling right */
  88     y >>= silk_RSHIFT(lz, 1);
  89
  90     /* increment using fractional part of input */
  91     y = silk_SMLAWB(y, y, silk_SMULBB(213, frac_Q7));
  92
  93     return y;
  94 }
  95
  96 /* Divide two int32 values and return result as int32 in a given Q-domain */
  97 static OPUS_INLINE opus_int32 silk_DIV32_varQ(   /* O    returns a good approximation of "(a32 << Qres) / b32" */
  98     const opus_int32     a32,               /* I    numerator (Q0)                  */
  99     const opus_int32     b32,               /* I    denominator (Q0)                */
 100     const opus_int       Qres               /* I    Q-domain of result (>= 0)       */
 101 )
 102 {
 103     opus_int   a_headrm, b_headrm, lshift;
 104     opus_int32 b32_inv, a32_nrm, b32_nrm, result;
 105
 106     silk_assert( b32 != 0 );
 107     silk_assert( Qres >= 0 );
 108
 109     /* Compute number of bits head room and normalize inputs */
 110     a_headrm = silk_CLZ32( silk_abs(a32) ) - 1;
 111     a32_nrm = silk_LSHIFT(a32, a_headrm);                                       /* Q: a_headrm                  */
 112     b_headrm = silk_CLZ32( silk_abs(b32) ) - 1;
 113     b32_nrm = silk_LSHIFT(b32, b_headrm);                                       /* Q: b_headrm                  */
 114
 115     /* Inverse of b32, with 14 bits of precision */
 116     b32_inv = silk_DIV32_16( silk_int32_MAX >> 2, silk_RSHIFT(b32_nrm, 16) );   /* Q: 29 + 16 - b_headrm        */
 117
 118     /* First approximation */
 119     result = silk_SMULWB(a32_nrm, b32_inv);                                     /* Q: 29 + a_headrm - b_headrm  */
 120
 121     /* Compute residual by subtracting product of denominator and first approximation */
 122     /* It's OK to overflow because the final value of a32_nrm should always be small */
 123     a32_nrm = silk_SUB32_ovflw(a32_nrm, silk_LSHIFT_ovflw( silk_SMMUL(b32_nrm, result), 3 ));  /* Q: a_headrm   */
 124
 125     /* Refinement */
 126     result = silk_SMLAWB(result, a32_nrm, b32_inv);                             /* Q: 29 + a_headrm - b_headrm  */
 127
 128     /* Convert to Qres domain */
 129     lshift = 29 + a_headrm - b_headrm - Qres;
 130     if( lshift < 0 ) {
 131         return silk_LSHIFT_SAT32(result, -lshift);
 132     } else {
 133         if( lshift < 32){
 134             return silk_RSHIFT(result, lshift);
 135         } else {
 136             /* Avoid undefined result */
 137             return 0;
 138         }
 139     }
 140 }
 141
 142 /* Invert int32 value and return result as int32 in a given Q-domain */
 143 static OPUS_INLINE opus_int32 silk_INVERSE32_varQ(   /* O    returns a good approximation of "(1 << Qres) / b32" */
 144     const opus_int32     b32,                   /* I    denominator (Q0)                */
 145     const opus_int       Qres                   /* I    Q-domain of result (> 0)        */
 146 )
 147 {
 148     opus_int   b_headrm, lshift;
 149     opus_int32 b32_inv, b32_nrm, err_Q32, result;
 150
 151     silk_assert( b32 != 0 );
 152     silk_assert( Qres > 0 );
 153
 154     /* Compute number of bits head room and normalize input */
 155     b_headrm = silk_CLZ32( silk_abs(b32) ) - 1;
 156     b32_nrm = silk_LSHIFT(b32, b_headrm);                                       /* Q: b_headrm                */
 157
 158     /* Inverse of b32, with 14 bits of precision */
 159     b32_inv = silk_DIV32_16( silk_int32_MAX >> 2, silk_RSHIFT(b32_nrm, 16) );   /* Q: 29 + 16 - b_headrm    */
 160
 161     /* First approximation */
 162     result = silk_LSHIFT(b32_inv, 16);                                          /* Q: 61 - b_headrm            */
 163
 164     /* Compute residual by subtracting product of denominator and first approximation from one */
 165     err_Q32 = silk_LSHIFT( ((opus_int32)1<<29) - silk_SMULWB(b32_nrm, b32_inv), 3 );        /* Q32                        */
 166
 167     /* Refinement */
 168     result = silk_SMLAWW(result, err_Q32, b32_inv);                             /* Q: 61 - b_headrm            */
 169
 170     /* Convert to Qres domain */
 171     lshift = 61 - b_headrm - Qres;
 172     if( lshift <= 0 ) {
 173         return silk_LSHIFT_SAT32(result, -lshift);
 174     } else {
 175         if( lshift < 32){
 176             return silk_RSHIFT(result, lshift);
 177         }else{
 178             /* Avoid undefined result */
 179             return 0;
 180         }
 181     }
 182 }
 183
 184 #ifdef  __cplusplus
 185 }
 186 #endif
 187
 188 #endif /* SILK_FIX_INLINES_H */