Line data    Source code

       1             : /*
       2             :  *  Copyright (c) 2012 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             : #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
      12             : 
      13             : #include "webrtc/base/checks.h"
      14             : 
      15           0 : size_t WebRtcSpl_AutoCorrelation(const int16_t* in_vector,
      16             :                                  size_t in_vector_length,
      17             :                                  size_t order,
      18             :                                  int32_t* result,
      19             :                                  int* scale) {
      20           0 :   int32_t sum = 0;
      21           0 :   size_t i = 0, j = 0;
      22           0 :   int16_t smax = 0;
      23           0 :   int scaling = 0;
      24             : 
      25           0 :   RTC_DCHECK_LE(order, in_vector_length);
      26             : 
      27             :   // Find the maximum absolute value of the samples.
      28           0 :   smax = WebRtcSpl_MaxAbsValueW16(in_vector, in_vector_length);
      29             : 
      30             :   // In order to avoid overflow when computing the sum we should scale the
      31             :   // samples so that (in_vector_length * smax * smax) will not overflow.
      32           0 :   if (smax == 0) {
      33           0 :     scaling = 0;
      34             :   } else {
      35             :     // Number of bits in the sum loop.
      36           0 :     int nbits = WebRtcSpl_GetSizeInBits((uint32_t)in_vector_length);
      37             :     // Number of bits to normalize smax.
      38           0 :     int t = WebRtcSpl_NormW32(WEBRTC_SPL_MUL(smax, smax));
      39             : 
      40           0 :     if (t > nbits) {
      41           0 :       scaling = 0;
      42             :     } else {
      43           0 :       scaling = nbits - t;
      44             :     }
      45             :   }
      46             : 
      47             :   // Perform the actual correlation calculation.
      48           0 :   for (i = 0; i < order + 1; i++) {
      49           0 :     sum = 0;
      50             :     /* Unroll the loop to improve performance. */
      51           0 :     for (j = 0; i + j + 3 < in_vector_length; j += 4) {
      52           0 :       sum += (in_vector[j + 0] * in_vector[i + j + 0]) >> scaling;
      53           0 :       sum += (in_vector[j + 1] * in_vector[i + j + 1]) >> scaling;
      54           0 :       sum += (in_vector[j + 2] * in_vector[i + j + 2]) >> scaling;
      55           0 :       sum += (in_vector[j + 3] * in_vector[i + j + 3]) >> scaling;
      56             :     }
      57           0 :     for (; j < in_vector_length - i; j++) {
      58           0 :       sum += (in_vector[j] * in_vector[i + j]) >> scaling;
      59             :     }
      60           0 :     *result++ = sum;
      61             :   }
      62             : 
      63           0 :   *scale = scaling;
      64           0 :   return order + 1;
      65             : }