webRTC中回声消除（AEC）模块的编译与测试

整体过程同webRTC降噪（NS）、自动增益控制（AGC）模块的编译与测试一样，只是在aec_rdft.c文件中可能会报错，局部变量ip跟全局变量冲突的问题，可以将局部变量重新命名一下，就可以通过编译了。

修改后的代码如下

/*
 * http://www.kurims.kyoto-u.ac.jp/~ooura/fft.html
 * Copyright Takuya OOURA, 1996-2001
 *
 * You may use, copy, modify and distribute this code for any purpose (include
 * commercial use) and without fee. Please refer to this package when you modify
 * this code.
 *
 * Changes by the WebRTC authors:
 *    - Trivial type modifications.
 *    - Minimal code subset to do rdft of length 128.
 *    - Optimizations because of known length.
 *
 *  All changes are covered by the WebRTC license and IP grant:
 *  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.
 */

#include "webrtc/modules/audio_processing/aec/aec_rdft.h"

#include 

#include "webrtc/system_wrappers/interface/cpu_features_wrapper.h"
#include "webrtc/typedefs.h"

// constants shared by all paths (C, SSE2).
float rdft_w[64];
// constants used by the C path.
float rdft_wk3ri_first[32];
float rdft_wk3ri_second[32];
// constants used by SSE2 but initialized in C path.
ALIGN16_BEG float ALIGN16_END rdft_wk1r[32];
ALIGN16_BEG float ALIGN16_END rdft_wk2r[32];
ALIGN16_BEG float ALIGN16_END rdft_wk3r[32];
ALIGN16_BEG float ALIGN16_END rdft_wk1i[32];
ALIGN16_BEG float ALIGN16_END rdft_wk2i[32];
ALIGN16_BEG float ALIGN16_END rdft_wk3i[32];
ALIGN16_BEG float ALIGN16_END cftmdl_wk1r[4];

static int ip[16];

static void bitrv2_32(int* ip1, float* a) {
  const int n = 32;
  int j, j1, k, k1, m, m2;
  float xr, xi, yr, yi;

  ip1[0] = 0;
  {
    int l = n;
    m = 1;
    while ((m <<3) >= 1;
      for (j = 0; j >25) + ((k >> 1)<<5).
      (e) Hard-coding of the offsets to completely eliminates index
          calculations.
  */

  unsigned int j, j1, k, k1;
  float xr, xi, yr, yi;

  static const int ip2[4] = {0, 64, 32, 96};
  for (k = 0; k <4; k++) {
    for (j = 0; j > 1;
  delta = atanf(1.0f) / nwh;
  rdft_w[0] = 1;
  rdft_w[1] = 0;
  rdft_w[nwh] = cosf(delta * nwh);
  rdft_w[nwh + 1] = rdft_w[nwh];
  for (j = 2; j > 1;
  delta = atanf(1.0f) / nch;
  c[0] = cosf(delta * nch);
  c[nch] = 0.5f * c[0];
  for (j = 1; j  
 
测试效果如下