Add audio stretching as a configuration option

Source/Core/AudioCommon/Mixer.cpp

@@ -122,18 +122,26 @@ unsigned int CMixer::MixerFifo::Mix(short* samples, unsigned int numSamples,
   return actual_sample_count;
 }
 
-unsigned int CMixer::Mix(short* samples, unsigned int num_samples, bool consider_framelimit)
+unsigned int CMixer::Mix(short* samples, unsigned int num_samples)
 {
   if (!samples)
     return 0;
 
   memset(samples, 0, num_samples * 2 * sizeof(short));
 
-  unsigned int actual_samples = m_dma_mixer.Mix(samples, num_samples, false);
-  m_streaming_mixer.Mix(samples, num_samples, false);
-  m_wiimote_speaker_mixer.Mix(samples, num_samples, false);
+  const bool stretch = SConfig::GetInstance().m_audio_stretch;
 
-  StretchAudio(samples, actual_samples, num_samples);
+  unsigned int actual_samples = m_dma_mixer.Mix(samples, num_samples, !stretch);
+  m_streaming_mixer.Mix(samples, num_samples, !stretch);
+  m_wiimote_speaker_mixer.Mix(samples, num_samples, !stretch);
+
+  if (stretch)
+  {
+    if (m_is_stretching != stretch)
+      m_sound_touch.clear();
+    StretchAudio(samples, actual_samples, num_samples);
+  }
+  m_is_stretching = stretch;
 
   return num_samples;
 }
@@ -144,10 +152,10 @@ void CMixer::StretchAudio(short* samples, unsigned int actual_samples, unsigned
 
   // We were given actual_samples number of samples, and num_samples were requested from us.
   double current_ratio = static_cast<double>(actual_samples) / static_cast<double>(num_samples);
-    
-  constexpr double MAXIMUM_LATENCY = 0.080;  // seconds
-  const double max_backlog = m_sampleRate * MAXIMUM_LATENCY;
-  double backlog_fullness = m_sound_touch.numSamples() / max_backlog;
+
+  const double max_latency = SConfig::GetInstance().m_audio_stretch_max_latency;
+  const double max_backlog = m_sampleRate * max_latency / 1000.0;
+  const double backlog_fullness = m_sound_touch.numSamples() / max_backlog;
   if (backlog_fullness > 1.0)
   {
     // Exceeded latency budget: Do not add more samples into FIFO.

Source/Core/AudioCommon/Mixer.h

@@ -20,7 +20,7 @@ public:
   ~CMixer();
 
   // Called from audio threads
-  unsigned int Mix(short* samples, unsigned int numSamples, bool consider_framelimit = true);
+  unsigned int Mix(short* samples, unsigned int numSamples);
 
   // Called from main thread
   void PushSamples(const short* samples, unsigned int num_samples);

Source/Core/Core/ConfigManager.cpp

@@ -249,6 +249,8 @@ void SConfig::SaveCoreSettings(IniFile& ini)
   core->Set("OverrideGCLang", bOverrideGCLanguage);
   core->Set("DPL2Decoder", bDPL2Decoder);
   core->Set("Latency", iLatency);
+  core->Set("AudioStretch", m_audio_stretch);
+  core->Set("AudioStretchMaxLatency", m_audio_stretch_max_latency);
   core->Set("MemcardAPath", m_strMemoryCardA);
   core->Set("MemcardBPath", m_strMemoryCardB);
   core->Set("AgpCartAPath", m_strGbaCartA);
@@ -567,6 +569,8 @@ void SConfig::LoadCoreSettings(IniFile& ini)
   core->Get("OverrideGCLang", &bOverrideGCLanguage, false);
   core->Get("DPL2Decoder", &bDPL2Decoder, false);
   core->Get("Latency", &iLatency, 2);
+  core->Get("AudioStretch", &m_audio_stretch, false);
+  core->Get("AudioStretchMaxLatency", &m_audio_stretch_max_latency, 80);
   core->Get("MemcardAPath", &m_strMemoryCardA);
   core->Get("MemcardBPath", &m_strMemoryCardB);
   core->Get("AgpCartAPath", &m_strGbaCartA);
@@ -827,6 +831,8 @@ void SConfig::LoadDefaults()
   bWii = false;
   bDPL2Decoder = false;
   iLatency = 14;
+  m_audio_stretch = false;
+  m_audio_stretch_max_latency = 80;
 
   iPosX = INT_MIN;
   iPosY = INT_MIN;

Source/Core/Core/ConfigManager.h

@@ -110,6 +110,8 @@ struct SConfig : NonCopyable
 
   bool bDPL2Decoder = false;
   int iLatency = 14;
+  bool m_audio_stretch = false;
+  int m_audio_stretch_max_latency = 80;
 
   bool bRunCompareServer = false;
   bool bRunCompareClient = false;