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/real_fft.h"
12 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
13 #include "webrtc/typedefs.h"
14
15 #include "testing/gtest/include/gtest/gtest.h"
16
17 namespace webrtc {
18 namespace {
19
20 // FFT order.
21 const int kOrder = 5;
22 // Lengths for real FFT's time and frequency bufffers.
23 // For N-point FFT, the length requirements from API are N and N+2 respectively.
24 const int kTimeDataLength = 1 << kOrder;
25 const int kFreqDataLength = (1 << kOrder) + 2;
26 // For complex FFT's time and freq buffer. The implementation requires
27 // 2*N 16-bit words.
28 const int kComplexFftDataLength = 2 << kOrder;
29 // Reference data for time signal.
30 const int16_t kRefData[kTimeDataLength] = {
31 11739, 6848, -8688, 31980, -30295, 25242, 27085, 19410,
32 -26299, 15607, -10791, 11778, -23819, 14498, -25772, 10076,
33 1173, 6848, -8688, 31980, -30295, 2522, 27085, 19410,
34 -2629, 5607, -3, 1178, -23819, 1498, -25772, 10076
35 };
36
37 class RealFFTTest : public ::testing::Test {
38 protected:
RealFFTTest()39 RealFFTTest() {
40 WebRtcSpl_Init();
41 }
42 };
43
TEST_F(RealFFTTest,CreateFailsOnBadInput)44 TEST_F(RealFFTTest, CreateFailsOnBadInput) {
45 RealFFT* fft = WebRtcSpl_CreateRealFFT(11);
46 EXPECT_TRUE(fft == NULL);
47 fft = WebRtcSpl_CreateRealFFT(-1);
48 EXPECT_TRUE(fft == NULL);
49 }
50
TEST_F(RealFFTTest,RealAndComplexMatch)51 TEST_F(RealFFTTest, RealAndComplexMatch) {
52 int i = 0;
53 int j = 0;
54 int16_t real_fft_time[kTimeDataLength] = {0};
55 int16_t real_fft_freq[kFreqDataLength] = {0};
56 // One common buffer for complex FFT's time and frequency data.
57 int16_t complex_fft_buff[kComplexFftDataLength] = {0};
58
59 // Prepare the inputs to forward FFT's.
60 memcpy(real_fft_time, kRefData, sizeof(kRefData));
61 for (i = 0, j = 0; i < kTimeDataLength; i += 1, j += 2) {
62 complex_fft_buff[j] = kRefData[i];
63 complex_fft_buff[j + 1] = 0; // Insert zero's to imaginary parts.
64 };
65
66 // Create and run real forward FFT.
67 RealFFT* fft = WebRtcSpl_CreateRealFFT(kOrder);
68 EXPECT_TRUE(fft != NULL);
69 EXPECT_EQ(0, WebRtcSpl_RealForwardFFT(fft, real_fft_time, real_fft_freq));
70
71 // Run complex forward FFT.
72 WebRtcSpl_ComplexBitReverse(complex_fft_buff, kOrder);
73 EXPECT_EQ(0, WebRtcSpl_ComplexFFT(complex_fft_buff, kOrder, 1));
74
75 // Verify the results between complex and real forward FFT.
76 for (i = 0; i < kFreqDataLength; i++) {
77 EXPECT_EQ(real_fft_freq[i], complex_fft_buff[i]);
78 }
79
80 // Prepare the inputs to inverse real FFT.
81 // We use whatever data in complex_fft_buff[] since we don't care
82 // about data contents. Only kFreqDataLength 16-bit words are copied
83 // from complex_fft_buff to real_fft_freq since remaining words (2nd half)
84 // are conjugate-symmetric to the first half in theory.
85 memcpy(real_fft_freq, complex_fft_buff, sizeof(real_fft_freq));
86
87 // Run real inverse FFT.
88 int real_scale = WebRtcSpl_RealInverseFFT(fft, real_fft_freq, real_fft_time);
89 EXPECT_GE(real_scale, 0);
90
91 // Run complex inverse FFT.
92 WebRtcSpl_ComplexBitReverse(complex_fft_buff, kOrder);
93 int complex_scale = WebRtcSpl_ComplexIFFT(complex_fft_buff, kOrder, 1);
94
95 // Verify the results between complex and real inverse FFT.
96 // They are not bit-exact, since complex IFFT doesn't produce
97 // exactly conjugate-symmetric data (between first and second half).
98 EXPECT_EQ(real_scale, complex_scale);
99 for (i = 0, j = 0; i < kTimeDataLength; i += 1, j += 2) {
100 EXPECT_LE(abs(real_fft_time[i] - complex_fft_buff[j]), 1);
101 }
102
103 WebRtcSpl_FreeRealFFT(fft);
104 }
105
106 } // namespace
107 } // namespace webrtc
108