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      1 /*
      2  *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
      3  *
      4  *  Use of this source code is governed by a BSD-style license
      5  *  that can be found in the LICENSE file in the root of the source
      6  *  tree. An additional intellectual property rights grant can be found
      7  *  in the file PATENTS.  All contributing project authors may
      8  *  be found in the AUTHORS file in the root of the source tree.
      9  */
     10 
     11 
     12 /*
     13  * This file contains implementations of the divisions
     14  * WebRtcSpl_DivU32U16()
     15  * WebRtcSpl_DivW32W16()
     16  * WebRtcSpl_DivW32W16ResW16()
     17  * WebRtcSpl_DivResultInQ31()
     18  * WebRtcSpl_DivW32HiLow()
     19  *
     20  * The description header can be found in signal_processing_library.h
     21  *
     22  */
     23 
     24 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
     25 
     26 uint32_t WebRtcSpl_DivU32U16(uint32_t num, uint16_t den)
     27 {
     28     // Guard against division with 0
     29     if (den != 0)
     30     {
     31         return (uint32_t)(num / den);
     32     } else
     33     {
     34         return (uint32_t)0xFFFFFFFF;
     35     }
     36 }
     37 
     38 int32_t WebRtcSpl_DivW32W16(int32_t num, int16_t den)
     39 {
     40     // Guard against division with 0
     41     if (den != 0)
     42     {
     43         return (int32_t)(num / den);
     44     } else
     45     {
     46         return (int32_t)0x7FFFFFFF;
     47     }
     48 }
     49 
     50 int16_t WebRtcSpl_DivW32W16ResW16(int32_t num, int16_t den)
     51 {
     52     // Guard against division with 0
     53     if (den != 0)
     54     {
     55         return (int16_t)(num / den);
     56     } else
     57     {
     58         return (int16_t)0x7FFF;
     59     }
     60 }
     61 
     62 int32_t WebRtcSpl_DivResultInQ31(int32_t num, int32_t den)
     63 {
     64     int32_t L_num = num;
     65     int32_t L_den = den;
     66     int32_t div = 0;
     67     int k = 31;
     68     int change_sign = 0;
     69 
     70     if (num == 0)
     71         return 0;
     72 
     73     if (num < 0)
     74     {
     75         change_sign++;
     76         L_num = -num;
     77     }
     78     if (den < 0)
     79     {
     80         change_sign++;
     81         L_den = -den;
     82     }
     83     while (k--)
     84     {
     85         div <<= 1;
     86         L_num <<= 1;
     87         if (L_num >= L_den)
     88         {
     89             L_num -= L_den;
     90             div++;
     91         }
     92     }
     93     if (change_sign == 1)
     94     {
     95         div = -div;
     96     }
     97     return div;
     98 }
     99 
    100 int32_t WebRtcSpl_DivW32HiLow(int32_t num, int16_t den_hi, int16_t den_low)
    101 {
    102     int16_t approx, tmp_hi, tmp_low, num_hi, num_low;
    103     int32_t tmpW32;
    104 
    105     approx = (int16_t)WebRtcSpl_DivW32W16((int32_t)0x1FFFFFFF, den_hi);
    106     // result in Q14 (Note: 3FFFFFFF = 0.5 in Q30)
    107 
    108     // tmpW32 = 1/den = approx * (2.0 - den * approx) (in Q30)
    109     tmpW32 = (den_hi * approx << 1) + ((den_low * approx >> 15) << 1);
    110     // tmpW32 = den * approx
    111 
    112     tmpW32 = (int32_t)0x7fffffffL - tmpW32; // result in Q30 (tmpW32 = 2.0-(den*approx))
    113 
    114     // Store tmpW32 in hi and low format
    115     tmp_hi = (int16_t)(tmpW32 >> 16);
    116     tmp_low = (int16_t)((tmpW32 - ((int32_t)tmp_hi << 16)) >> 1);
    117 
    118     // tmpW32 = 1/den in Q29
    119     tmpW32 = (tmp_hi * approx + (tmp_low * approx >> 15)) << 1;
    120 
    121     // 1/den in hi and low format
    122     tmp_hi = (int16_t)(tmpW32 >> 16);
    123     tmp_low = (int16_t)((tmpW32 - ((int32_t)tmp_hi << 16)) >> 1);
    124 
    125     // Store num in hi and low format
    126     num_hi = (int16_t)(num >> 16);
    127     num_low = (int16_t)((num - ((int32_t)num_hi << 16)) >> 1);
    128 
    129     // num * (1/den) by 32 bit multiplication (result in Q28)
    130 
    131     tmpW32 = num_hi * tmp_hi + (num_hi * tmp_low >> 15) +
    132         (num_low * tmp_hi >> 15);
    133 
    134     // Put result in Q31 (convert from Q28)
    135     tmpW32 = WEBRTC_SPL_LSHIFT_W32(tmpW32, 3);
    136 
    137     return tmpW32;
    138 }
    139