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278 lines
10 KiB
278 lines
10 KiB
/*
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* Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "audio/remix_resample.h"
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#include <cmath>
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#include "common_audio/resampler/include/push_resampler.h"
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#include "rtc_base/arraysize.h"
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#include "rtc_base/checks.h"
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#include "rtc_base/format_macros.h"
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#include "test/gtest.h"
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namespace webrtc {
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namespace voe {
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namespace {
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class UtilityTest : public ::testing::Test {
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protected:
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UtilityTest() {
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src_frame_.sample_rate_hz_ = 16000;
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src_frame_.samples_per_channel_ = src_frame_.sample_rate_hz_ / 100;
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src_frame_.num_channels_ = 1;
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dst_frame_.CopyFrom(src_frame_);
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golden_frame_.CopyFrom(src_frame_);
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}
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void RunResampleTest(int src_channels,
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int src_sample_rate_hz,
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int dst_channels,
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int dst_sample_rate_hz);
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PushResampler<int16_t> resampler_;
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AudioFrame src_frame_;
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AudioFrame dst_frame_;
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AudioFrame golden_frame_;
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};
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// Sets the signal value to increase by |data| with every sample. Floats are
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// used so non-integer values result in rounding error, but not an accumulating
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// error.
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void SetMonoFrame(float data, int sample_rate_hz, AudioFrame* frame) {
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frame->Mute();
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frame->num_channels_ = 1;
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frame->sample_rate_hz_ = sample_rate_hz;
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frame->samples_per_channel_ = rtc::CheckedDivExact(sample_rate_hz, 100);
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int16_t* frame_data = frame->mutable_data();
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for (size_t i = 0; i < frame->samples_per_channel_; i++) {
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frame_data[i] = static_cast<int16_t>(data * i);
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}
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}
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// Keep the existing sample rate.
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void SetMonoFrame(float data, AudioFrame* frame) {
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SetMonoFrame(data, frame->sample_rate_hz_, frame);
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}
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// Sets the signal value to increase by |left| and |right| with every sample in
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// each channel respectively.
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void SetStereoFrame(float left,
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float right,
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int sample_rate_hz,
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AudioFrame* frame) {
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frame->Mute();
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frame->num_channels_ = 2;
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frame->sample_rate_hz_ = sample_rate_hz;
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frame->samples_per_channel_ = rtc::CheckedDivExact(sample_rate_hz, 100);
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int16_t* frame_data = frame->mutable_data();
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for (size_t i = 0; i < frame->samples_per_channel_; i++) {
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frame_data[i * 2] = static_cast<int16_t>(left * i);
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frame_data[i * 2 + 1] = static_cast<int16_t>(right * i);
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}
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}
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// Keep the existing sample rate.
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void SetStereoFrame(float left, float right, AudioFrame* frame) {
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SetStereoFrame(left, right, frame->sample_rate_hz_, frame);
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}
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// Sets the signal value to increase by |ch1|, |ch2|, |ch3|, |ch4| with every
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// sample in each channel respectively.
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void SetQuadFrame(float ch1,
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float ch2,
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float ch3,
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float ch4,
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int sample_rate_hz,
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AudioFrame* frame) {
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frame->Mute();
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frame->num_channels_ = 4;
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frame->sample_rate_hz_ = sample_rate_hz;
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frame->samples_per_channel_ = rtc::CheckedDivExact(sample_rate_hz, 100);
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int16_t* frame_data = frame->mutable_data();
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for (size_t i = 0; i < frame->samples_per_channel_; i++) {
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frame_data[i * 4] = static_cast<int16_t>(ch1 * i);
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frame_data[i * 4 + 1] = static_cast<int16_t>(ch2 * i);
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frame_data[i * 4 + 2] = static_cast<int16_t>(ch3 * i);
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frame_data[i * 4 + 3] = static_cast<int16_t>(ch4 * i);
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}
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}
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void VerifyParams(const AudioFrame& ref_frame, const AudioFrame& test_frame) {
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EXPECT_EQ(ref_frame.num_channels_, test_frame.num_channels_);
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EXPECT_EQ(ref_frame.samples_per_channel_, test_frame.samples_per_channel_);
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EXPECT_EQ(ref_frame.sample_rate_hz_, test_frame.sample_rate_hz_);
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}
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// Computes the best SNR based on the error between |ref_frame| and
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// |test_frame|. It allows for up to a |max_delay| in samples between the
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// signals to compensate for the resampling delay.
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float ComputeSNR(const AudioFrame& ref_frame,
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const AudioFrame& test_frame,
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size_t max_delay) {
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VerifyParams(ref_frame, test_frame);
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float best_snr = 0;
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size_t best_delay = 0;
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for (size_t delay = 0; delay <= max_delay; delay++) {
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float mse = 0;
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float variance = 0;
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const int16_t* ref_frame_data = ref_frame.data();
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const int16_t* test_frame_data = test_frame.data();
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for (size_t i = 0;
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i < ref_frame.samples_per_channel_ * ref_frame.num_channels_ - delay;
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i++) {
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int error = ref_frame_data[i] - test_frame_data[i + delay];
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mse += error * error;
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variance += ref_frame_data[i] * ref_frame_data[i];
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}
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float snr = 100; // We assign 100 dB to the zero-error case.
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if (mse > 0)
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snr = 10 * std::log10(variance / mse);
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if (snr > best_snr) {
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best_snr = snr;
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best_delay = delay;
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}
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}
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printf("SNR=%.1f dB at delay=%" RTC_PRIuS "\n", best_snr, best_delay);
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return best_snr;
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}
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void VerifyFramesAreEqual(const AudioFrame& ref_frame,
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const AudioFrame& test_frame) {
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VerifyParams(ref_frame, test_frame);
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const int16_t* ref_frame_data = ref_frame.data();
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const int16_t* test_frame_data = test_frame.data();
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for (size_t i = 0;
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i < ref_frame.samples_per_channel_ * ref_frame.num_channels_; i++) {
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EXPECT_EQ(ref_frame_data[i], test_frame_data[i]);
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}
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}
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void UtilityTest::RunResampleTest(int src_channels,
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int src_sample_rate_hz,
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int dst_channels,
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int dst_sample_rate_hz) {
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PushResampler<int16_t> resampler; // Create a new one with every test.
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const int16_t kSrcCh1 = 30; // Shouldn't overflow for any used sample rate.
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const int16_t kSrcCh2 = 15;
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const int16_t kSrcCh3 = 22;
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const int16_t kSrcCh4 = 8;
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const float resampling_factor =
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(1.0 * src_sample_rate_hz) / dst_sample_rate_hz;
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const float dst_ch1 = resampling_factor * kSrcCh1;
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const float dst_ch2 = resampling_factor * kSrcCh2;
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const float dst_ch3 = resampling_factor * kSrcCh3;
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const float dst_ch4 = resampling_factor * kSrcCh4;
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const float dst_stereo_to_mono = (dst_ch1 + dst_ch2) / 2;
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const float dst_quad_to_mono = (dst_ch1 + dst_ch2 + dst_ch3 + dst_ch4) / 4;
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const float dst_quad_to_stereo_ch1 = (dst_ch1 + dst_ch2) / 2;
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const float dst_quad_to_stereo_ch2 = (dst_ch3 + dst_ch4) / 2;
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if (src_channels == 1)
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SetMonoFrame(kSrcCh1, src_sample_rate_hz, &src_frame_);
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else if (src_channels == 2)
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SetStereoFrame(kSrcCh1, kSrcCh2, src_sample_rate_hz, &src_frame_);
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else
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SetQuadFrame(kSrcCh1, kSrcCh2, kSrcCh3, kSrcCh4, src_sample_rate_hz,
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&src_frame_);
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if (dst_channels == 1) {
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SetMonoFrame(0, dst_sample_rate_hz, &dst_frame_);
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if (src_channels == 1)
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SetMonoFrame(dst_ch1, dst_sample_rate_hz, &golden_frame_);
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else if (src_channels == 2)
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SetMonoFrame(dst_stereo_to_mono, dst_sample_rate_hz, &golden_frame_);
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else
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SetMonoFrame(dst_quad_to_mono, dst_sample_rate_hz, &golden_frame_);
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} else {
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SetStereoFrame(0, 0, dst_sample_rate_hz, &dst_frame_);
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if (src_channels == 1)
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SetStereoFrame(dst_ch1, dst_ch1, dst_sample_rate_hz, &golden_frame_);
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else if (src_channels == 2)
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SetStereoFrame(dst_ch1, dst_ch2, dst_sample_rate_hz, &golden_frame_);
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else
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SetStereoFrame(dst_quad_to_stereo_ch1, dst_quad_to_stereo_ch2,
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dst_sample_rate_hz, &golden_frame_);
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}
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// The sinc resampler has a known delay, which we compute here. Multiplying by
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// two gives us a crude maximum for any resampling, as the old resampler
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// typically (but not always) has lower delay.
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static const size_t kInputKernelDelaySamples = 16;
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const size_t max_delay = static_cast<size_t>(
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static_cast<double>(dst_sample_rate_hz) / src_sample_rate_hz *
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kInputKernelDelaySamples * dst_channels * 2);
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printf("(%d, %d Hz) -> (%d, %d Hz) ", // SNR reported on the same line later.
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src_channels, src_sample_rate_hz, dst_channels, dst_sample_rate_hz);
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RemixAndResample(src_frame_, &resampler, &dst_frame_);
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if (src_sample_rate_hz == 96000 && dst_sample_rate_hz == 8000) {
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// The sinc resampler gives poor SNR at this extreme conversion, but we
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// expect to see this rarely in practice.
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EXPECT_GT(ComputeSNR(golden_frame_, dst_frame_, max_delay), 14.0f);
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} else {
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EXPECT_GT(ComputeSNR(golden_frame_, dst_frame_, max_delay), 46.0f);
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}
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}
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TEST_F(UtilityTest, RemixAndResampleCopyFrameSucceeds) {
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// Stereo -> stereo.
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SetStereoFrame(10, 10, &src_frame_);
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SetStereoFrame(0, 0, &dst_frame_);
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RemixAndResample(src_frame_, &resampler_, &dst_frame_);
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VerifyFramesAreEqual(src_frame_, dst_frame_);
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// Mono -> mono.
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SetMonoFrame(20, &src_frame_);
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SetMonoFrame(0, &dst_frame_);
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RemixAndResample(src_frame_, &resampler_, &dst_frame_);
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VerifyFramesAreEqual(src_frame_, dst_frame_);
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}
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TEST_F(UtilityTest, RemixAndResampleMixingOnlySucceeds) {
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// Stereo -> mono.
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SetStereoFrame(0, 0, &dst_frame_);
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SetMonoFrame(10, &src_frame_);
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SetStereoFrame(10, 10, &golden_frame_);
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RemixAndResample(src_frame_, &resampler_, &dst_frame_);
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VerifyFramesAreEqual(dst_frame_, golden_frame_);
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// Mono -> stereo.
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SetMonoFrame(0, &dst_frame_);
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SetStereoFrame(10, 20, &src_frame_);
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SetMonoFrame(15, &golden_frame_);
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RemixAndResample(src_frame_, &resampler_, &dst_frame_);
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VerifyFramesAreEqual(golden_frame_, dst_frame_);
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}
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TEST_F(UtilityTest, RemixAndResampleSucceeds) {
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const int kSampleRates[] = {8000, 16000, 32000, 44100, 48000, 96000};
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const int kSampleRatesSize = arraysize(kSampleRates);
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const int kSrcChannels[] = {1, 2, 4};
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const int kSrcChannelsSize = arraysize(kSrcChannels);
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const int kDstChannels[] = {1, 2};
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const int kDstChannelsSize = arraysize(kDstChannels);
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for (int src_rate = 0; src_rate < kSampleRatesSize; src_rate++) {
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for (int dst_rate = 0; dst_rate < kSampleRatesSize; dst_rate++) {
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for (int src_channel = 0; src_channel < kSrcChannelsSize; src_channel++) {
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for (int dst_channel = 0; dst_channel < kDstChannelsSize;
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dst_channel++) {
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RunResampleTest(kSrcChannels[src_channel], kSampleRates[src_rate],
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kDstChannels[dst_channel], kSampleRates[dst_rate]);
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}
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}
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}
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}
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}
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} // namespace
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} // namespace voe
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} // namespace webrtc
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