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AudioCommon: extract AudioStretcher class for time-stretching

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This commit is contained in:
Michael Maltese 2017-04-23 19:08:33 -07:00
parent a4508e85e8
commit 87a467fe42
7 changed files with 123 additions and 75 deletions
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2
Source/Core/AudioCommon/AudioCommon.vcxproj
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@ -38,6 +38,7 @@
<ItemGroup>
<ClCompile Include="aldlist.cpp" />
<ClCompile Include="AudioCommon.cpp" />
<ClCompile Include="AudioStretcher.cpp" />
<ClCompile Include="CubebStream.cpp" />
<ClCompile Include="CubebUtils.cpp" />
<ClCompile Include="DPL2Decoder.cpp" />
@ -54,6 +55,7 @@
<ClInclude Include="aldlist.h" />
<ClInclude Include="AlsaSoundStream.h" />
<ClInclude Include="AudioCommon.h" />
<ClInclude Include="AudioStretcher.h" />
<ClInclude Include="CoreAudioSoundStream.h" />
<ClInclude Include="CubebStream.h" />
<ClInclude Include="CubebUtils.h" />

2
Source/Core/AudioCommon/AudioCommon.vcxproj.filters
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@ -8,6 +8,7 @@
<ItemGroup>
<ClCompile Include="aldlist.cpp" />
<ClCompile Include="AudioCommon.cpp" />
<ClCompile Include="AudioStretcher.cpp" />
<ClCompile Include="CubebUtils.cpp" />
<ClCompile Include="DPL2Decoder.cpp" />
<ClCompile Include="Mixer.cpp" />
@ -31,6 +32,7 @@
<ItemGroup>
<ClInclude Include="aldlist.h" />
<ClInclude Include="AudioCommon.h" />
<ClInclude Include="AudioStretcher.h" />
<ClInclude Include="CubebUtils.h" />
<ClInclude Include="DPL2Decoder.h" />
<ClInclude Include="Mixer.h" />

85
Source/Core/AudioCommon/AudioStretcher.cpp Normal file
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@ -0,0 +1,85 @@
// Copyright 2017 Dolphin Emulator Project
// Licensed under GPLv2+
// Refer to the license.txt file included.
#include <cmath>
#include "AudioCommon/AudioStretcher.h"
#include "Common/Logging/Log.h"
#include "Core/ConfigManager.h"
namespace AudioCommon
{
AudioStretcher::AudioStretcher(unsigned int sample_rate) : m_sample_rate(sample_rate)
{
m_sound_touch.setChannels(2);
m_sound_touch.setSampleRate(sample_rate);
m_sound_touch.setPitch(1.0);
m_sound_touch.setTempo(1.0);
m_sound_touch.setSetting(SETTING_USE_QUICKSEEK, 0);
m_sound_touch.setSetting(SETTING_SEQUENCE_MS, 62);
m_sound_touch.setSetting(SETTING_SEEKWINDOW_MS, 28);
m_sound_touch.setSetting(SETTING_OVERLAP_MS, 8);
}
void AudioStretcher::Clear()
{
m_sound_touch.clear();
}
void AudioStretcher::StretchAudio(const short* in, unsigned int num_in, short* out,
unsigned int num_out)
{
const double time_delta = static_cast<double>(num_out) / m_sample_rate; // seconds
// We were given actual_samples number of samples, and num_samples were requested from us.
double current_ratio = static_cast<double>(num_in) / static_cast<double>(num_out);
const double max_latency = SConfig::GetInstance().m_audio_stretch_max_latency;
const double max_backlog = m_sample_rate * max_latency / 1000.0 / m_stretch_ratio;
const double backlog_fullness = m_sound_touch.numSamples() / max_backlog;
if (backlog_fullness > 5.0)
{
// Too many samples in backlog: Don't push anymore on
num_in = 0;
}
// We ideally want the backlog to be about 50% full.
// This gives some headroom both ways to prevent underflow and overflow.
// We tweak current_ratio to encourage this.
constexpr double tweak_time_scale = 0.5; // seconds
current_ratio *= 1.0 + 2.0 * (backlog_fullness - 0.5) * (time_delta / tweak_time_scale);
// This low-pass filter smoothes out variance in the calculated stretch ratio.
// The time-scale determines how responsive this filter is.
constexpr double lpf_time_scale = 1.0; // seconds
const double lpf_gain = 1.0 - std::exp(-time_delta / lpf_time_scale);
m_stretch_ratio += lpf_gain * (current_ratio - m_stretch_ratio);
// Place a lower limit of 10% speed. When a game boots up, there will be
// many silence samples. These do not need to be timestretched.
m_stretch_ratio = std::max(m_stretch_ratio, 0.1);
m_sound_touch.setTempo(m_stretch_ratio);
DEBUG_LOG(AUDIO, "Audio stretching: samples:%u/%u ratio:%f backlog:%f gain: %f", num_in, num_out,
m_stretch_ratio, backlog_fullness, lpf_gain);
m_sound_touch.putSamples(in, num_in);
const size_t samples_received = m_sound_touch.receiveSamples(out, num_out);
if (samples_received != 0)
{
m_last_stretched_sample[0] = out[samples_received * 2 - 2];
m_last_stretched_sample[1] = out[samples_received * 2 - 1];
}
// Perform padding if we've run out of samples.
for (size_t i = samples_received; i < num_out; i++)
{
out[i * 2 + 0] = m_last_stretched_sample[0];
out[i * 2 + 1] = m_last_stretched_sample[1];
}
}
} // namespace AudioCommon

27
Source/Core/AudioCommon/AudioStretcher.h Normal file
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@ -0,0 +1,27 @@
// Copyright 2017 Dolphin Emulator Project
// Licensed under GPLv2+
// Refer to the license.txt file included.
#pragma once
#include <array>
#include <soundtouch/SoundTouch.h>
namespace AudioCommon
{
class AudioStretcher
{
public:
AudioStretcher(unsigned int sample_rate);
void StretchAudio(const short* in, unsigned int num_in, short* out, unsigned int num_out);
void Clear();
private:
unsigned int m_sample_rate;
std::array<short, 2> m_last_stretched_sample = {};
soundtouch::SoundTouch m_sound_touch;
double m_stretch_ratio = 1.0;
};
} // AudioCommon

1
Source/Core/AudioCommon/CMakeLists.txt
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@ -1,5 +1,6 @@
set(SRCS
AudioCommon.cpp
AudioStretcher.cpp
CubebStream.cpp
CubebUtils.cpp
DPL2Decoder.cpp

71
Source/Core/AudioCommon/Mixer.cpp
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@ -14,19 +14,10 @@
#include "Common/Swap.h"
#include "Core/ConfigManager.h"
CMixer::CMixer(unsigned int BackendSampleRate) : m_sampleRate(BackendSampleRate)
CMixer::CMixer(unsigned int BackendSampleRate)
: m_sampleRate(BackendSampleRate), m_stretcher(BackendSampleRate)
{
INFO_LOG(AUDIO_INTERFACE, "Mixer is initialized");
m_sound_touch.setChannels(2);
m_sound_touch.setSampleRate(BackendSampleRate);
m_sound_touch.setPitch(1.0);
m_sound_touch.setTempo(1.0);
m_sound_touch.setSetting(SETTING_USE_QUICKSEEK, 0);
m_sound_touch.setSetting(SETTING_SEQUENCE_MS, 62);
m_sound_touch.setSetting(SETTING_SEEKWINDOW_MS, 28);
m_sound_touch.setSetting(SETTING_OVERLAP_MS, 8);
DPL2Reset();
}
@ -146,10 +137,10 @@ unsigned int CMixer::Mix(short* samples, unsigned int num_samples)
if (!m_is_stretching)
{
m_sound_touch.clear();
m_stretcher.Clear();
m_is_stretching = true;
}
StretchAudio(m_stretch_buffer.data(), available_samples, samples, num_samples);
m_stretcher.StretchAudio(m_stretch_buffer.data(), available_samples, samples, num_samples);
}
else
{
@ -181,60 +172,6 @@ unsigned int CMixer::MixSurround(float* samples, unsigned int num_samples)
return available_samples;
}
void CMixer::StretchAudio(const short* in, unsigned int num_in, short* out, unsigned int num_out)
{
const double time_delta = static_cast<double>(num_out) / m_sampleRate; // seconds
// We were given actual_samples number of samples, and num_samples were requested from us.
double current_ratio = static_cast<double>(num_in) / static_cast<double>(num_out);
const double max_latency = SConfig::GetInstance().m_audio_stretch_max_latency;
const double max_backlog = m_sampleRate * max_latency / 1000.0 / m_stretch_ratio;
const double backlog_fullness = m_sound_touch.numSamples() / max_backlog;
if (backlog_fullness > 5.0)
{
// Too many samples in backlog: Don't push anymore on
num_in = 0;
}
// We ideally want the backlog to be about 50% full.
// This gives some headroom both ways to prevent underflow and overflow.
// We tweak current_ratio to encourage this.
constexpr double tweak_time_scale = 0.5; // seconds
current_ratio *= 1.0 + 2.0 * (backlog_fullness - 0.5) * (time_delta / tweak_time_scale);
// This low-pass filter smoothes out variance in the calculated stretch ratio.
// The time-scale determines how responsive this filter is.
constexpr double lpf_time_scale = 1.0; // seconds
const double m_lpf_gain = 1.0 - std::exp(-time_delta / lpf_time_scale);
m_stretch_ratio += m_lpf_gain * (current_ratio - m_stretch_ratio);
// Place a lower limit of 10% speed. When a game boots up, there will be
// many silence samples. These do not need to be timestretched.
m_stretch_ratio = std::max(m_stretch_ratio, 0.1);
m_sound_touch.setTempo(m_stretch_ratio);
DEBUG_LOG(AUDIO, "Audio stretching: samples:%u/%u ratio:%f backlog:%f gain: %f", num_in, num_out,
m_stretch_ratio, backlog_fullness, m_lpf_gain);
m_sound_touch.putSamples(in, num_in);
const size_t samples_received = m_sound_touch.receiveSamples(out, num_out);
if (samples_received != 0)
{
m_last_stretched_sample[0] = out[samples_received * 2 - 2];
m_last_stretched_sample[1] = out[samples_received * 2 - 1];
}
// Preform padding if we've run out of samples.
for (size_t i = samples_received; i < num_out; i++)
{
out[i * 2 + 0] = m_last_stretched_sample[0];
out[i * 2 + 1] = m_last_stretched_sample[1];
}
}
void CMixer::MixerFifo::PushSamples(const short* samples, unsigned int num_samples)
{
// Cache access in non-volatile variable

10
Source/Core/AudioCommon/Mixer.h
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@ -7,12 +7,10 @@
#include <array>
#include <atomic>
#include "AudioCommon/AudioStretcher.h"
#include "AudioCommon/WaveFile.h"
#include "Common/CommonTypes.h"
#include <soundtouch/STTypes.h>
#include <soundtouch/SoundTouch.h>
class CMixer final
{
public:
@ -76,17 +74,13 @@ private:
u32 m_frac = 0;
};
void StretchAudio(const short* in, unsigned int num_in, short* out, unsigned int num_out);
MixerFifo m_dma_mixer{this, 32000};
MixerFifo m_streaming_mixer{this, 48000};
MixerFifo m_wiimote_speaker_mixer{this, 3000};
unsigned int m_sampleRate;
bool m_is_stretching = false;
soundtouch::SoundTouch m_sound_touch;
double m_stretch_ratio = 1.0;
std::array<short, 2> m_last_stretched_sample = {};
AudioCommon::AudioStretcher m_stretcher;
std::array<short, MAX_SAMPLES * 2> m_stretch_buffer;
std::array<float, MAX_SAMPLES * 2> m_float_conversion_buffer;