Move aec_resampler.c to be built using C++

webrtc/modules/audio_processing/aec/aec_resampler.c

-/*
- *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-/* Resamples a signal to an arbitrary rate. Used by the AEC to compensate for
- * clock skew by resampling the farend signal.
- */
-
-#include "webrtc/modules/audio_processing/aec/aec_resampler.h"
-
-#include <assert.h>
-#include <math.h>
-#include <stdlib.h>
-#include <string.h>
-
-#include "webrtc/modules/audio_processing/aec/aec_core.h"
-
-enum { kEstimateLengthFrames = 400 };
-
-typedef struct {
-  float buffer[kResamplerBufferSize];
-  float position;
-
-  int deviceSampleRateHz;
-  int skewData[kEstimateLengthFrames];
-  int skewDataIndex;
-  float skewEstimate;
-} AecResampler;
-
-static int EstimateSkew(const int* rawSkew,
-                        int size,
-                        int absLimit,
-                        float* skewEst);
-
-void* WebRtcAec_CreateResampler() {
-  return malloc(sizeof(AecResampler));
-}
-
-int WebRtcAec_InitResampler(void* resampInst, int deviceSampleRateHz) {
-  AecResampler* obj = (AecResampler*)resampInst;
-  memset(obj->buffer, 0, sizeof(obj->buffer));
-  obj->position = 0.0;
-
-  obj->deviceSampleRateHz = deviceSampleRateHz;
-  memset(obj->skewData, 0, sizeof(obj->skewData));
-  obj->skewDataIndex = 0;
-  obj->skewEstimate = 0.0;
-
-  return 0;
-}
-
-void WebRtcAec_FreeResampler(void* resampInst) {
-  AecResampler* obj = (AecResampler*)resampInst;
-  free(obj);
-}
-
-void WebRtcAec_ResampleLinear(void* resampInst,
-                              const float* inspeech,
-                              size_t size,
-                              float skew,
-                              float* outspeech,
-                              size_t* size_out) {
-  AecResampler* obj = (AecResampler*)resampInst;
-
-  float* y;
-  float be, tnew;
-  size_t tn, mm;
-
-  assert(size <= 2 * FRAME_LEN);
-  assert(resampInst != NULL);
-  assert(inspeech != NULL);
-  assert(outspeech != NULL);
-  assert(size_out != NULL);
-
-  // Add new frame data in lookahead
-  memcpy(&obj->buffer[FRAME_LEN + kResamplingDelay], inspeech,
-         size * sizeof(inspeech[0]));
-
-  // Sample rate ratio
-  be = 1 + skew;
-
-  // Loop over input frame
-  mm = 0;
-  y = &obj->buffer[FRAME_LEN];  // Point at current frame
-
-  tnew = be * mm + obj->position;
-  tn = (size_t)tnew;
-
-  while (tn < size) {
-    // Interpolation
-    outspeech[mm] = y[tn] + (tnew - tn) * (y[tn + 1] - y[tn]);
-    mm++;
-
-    tnew = be * mm + obj->position;
-    tn = (int)tnew;
-  }
-
-  *size_out = mm;
-  obj->position += (*size_out) * be - size;
-
-  // Shift buffer
-  memmove(obj->buffer, &obj->buffer[size],
-          (kResamplerBufferSize - size) * sizeof(obj->buffer[0]));
-}
-
-int WebRtcAec_GetSkew(void* resampInst, int rawSkew, float* skewEst) {
-  AecResampler* obj = (AecResampler*)resampInst;
-  int err = 0;
-
-  if (obj->skewDataIndex < kEstimateLengthFrames) {
-    obj->skewData[obj->skewDataIndex] = rawSkew;
-    obj->skewDataIndex++;
-  } else if (obj->skewDataIndex == kEstimateLengthFrames) {
-    err = EstimateSkew(obj->skewData, kEstimateLengthFrames,
-                       obj->deviceSampleRateHz, skewEst);
-    obj->skewEstimate = *skewEst;
-    obj->skewDataIndex++;
-  } else {
-    *skewEst = obj->skewEstimate;
-  }
-
-  return err;
-}
-
-int EstimateSkew(const int* rawSkew,
-                 int size,
-                 int deviceSampleRateHz,
-                 float* skewEst) {
-  const int absLimitOuter = (int)(0.04f * deviceSampleRateHz);
-  const int absLimitInner = (int)(0.0025f * deviceSampleRateHz);
-  int i = 0;
-  int n = 0;
-  float rawAvg = 0;
-  float err = 0;
-  float rawAbsDev = 0;
-  int upperLimit = 0;
-  int lowerLimit = 0;
-  float cumSum = 0;
-  float x = 0;
-  float x2 = 0;
-  float y = 0;
-  float xy = 0;
-  float xAvg = 0;
-  float denom = 0;
-  float skew = 0;
-
-  *skewEst = 0;  // Set in case of error below.
-  for (i = 0; i < size; i++) {
-    if ((rawSkew[i] < absLimitOuter && rawSkew[i] > -absLimitOuter)) {
-      n++;
-      rawAvg += rawSkew[i];
-    }
-  }
-
-  if (n == 0) {
-    return -1;
-  }
-  assert(n > 0);
-  rawAvg /= n;
-
-  for (i = 0; i < size; i++) {
-    if ((rawSkew[i] < absLimitOuter && rawSkew[i] > -absLimitOuter)) {
-      err = rawSkew[i] - rawAvg;
-      rawAbsDev += err >= 0 ? err : -err;
-    }
-  }
-  assert(n > 0);
-  rawAbsDev /= n;
-  upperLimit = (int)(rawAvg + 5 * rawAbsDev + 1);  // +1 for ceiling.
-  lowerLimit = (int)(rawAvg - 5 * rawAbsDev - 1);  // -1 for floor.
-
-  n = 0;
-  for (i = 0; i < size; i++) {
-    if ((rawSkew[i] < absLimitInner && rawSkew[i] > -absLimitInner) ||
-        (rawSkew[i] < upperLimit && rawSkew[i] > lowerLimit)) {
-      n++;
-      cumSum += rawSkew[i];
-      x += n;
-      x2 += n * n;
-      y += cumSum;
-      xy += n * cumSum;
-    }
-  }
-
-  if (n == 0) {
-    return -1;
-  }
-  assert(n > 0);
-  xAvg = x / n;
-  denom = x2 - xAvg * x;
-
-  if (denom != 0) {
-    skew = (xy - xAvg * y) / denom;
-  }
-
-  *skewEst = skew;
-  return 0;
-}