Refactor latency settings

- Perform limit handling in DevicePrefs rather than in AudioIO.
- Get converted preference in AudioIoCallback through
  GetConvertedLatencyPreference().
- Properly convert milliseconds to samples.

Aso fixes #281, where an incorrect latency preference was being saved.

Reference-to: https://codeberg.org/tenacityteam/tenacity/issues/281
Signed-off-by: Avery King <[email protected]>

src/AudioIO.cpp

@@ -586,31 +586,18 @@ using std::min;
 
 /// @brief Converts the latency preference to samples and updates the user's
 /// preference.
-void AudioIoCallback::ConvertLatencyPreference()
+long AudioIoCallback::GetConvertedLatencyPreference()
 {
    // Find out frames per buffer
-   double latency = AudioIOLatencyDuration.Read();
+   long latency = AudioIOLatencyDuration.Read();
    bool isMilliseconds = AudioIOLatencyUnit.Read() == L"milliseconds";
 
    if (isMilliseconds)
    {
-      // The minimum latency setting is limited to either 32 samples or an
-      // equivalent time in milliseconds at the current sample rate at minimum.
-      // If the preference is below this setting, automatically set it to
-      // either 32 samples or the equivalent sample rate based on mRate.
-      latency *= mRate;
-      if (latency < 32.0)
-      {
-         latency = 32.0;
-      }
-
-      // Save the new latency preference.
-      AudioIOLatencyDuration.Write(latency / (mRate/1000));
-   } else if (latency < 32)
-   {
-      latency = 32;
-      AudioIOLatencyDuration.Write(latency);
+      latency *= mRate / 1000;
    }
+
+   return latency;
 }
 
 AudioIO *AudioIO::Get()
@@ -1335,11 +1322,9 @@ bool AudioIO::StartPortAudioStream(const AudioIOStartStreamOptions &options,
       maxTries = 5;
 #endif
 
-   ConvertLatencyPreference();
-
    UpdateBuffers();
 
-   unsigned long latency = AudioIOLatencyDuration.Read();
+   unsigned long latency = GetConvertedLatencyPreference();
 
    for (unsigned int tries = 0; tries < maxTries; tries++) {
       mLastPaError = Pa_OpenStream( &mPortStreamV19,
@@ -3615,9 +3600,7 @@ void AudioIoCallback::UpdateBuffers()
       return;
    }
 
-   ConvertLatencyPreference();
-
-   unsigned long newBufferSize = AudioIOLatencyDuration.Read();
+   unsigned long newBufferSize = GetConvertedLatencyPreference();
    auto& memoryManager = AudioMemoryManager::Get();
 
    mTemporaryBuffer.reset();

src/AudioIO.h

@@ -388,7 +388,15 @@ class TENACITY_DLL_API AudioIoCallback /* not final */
 
 protected:
 
-   void ConvertLatencyPreference();
+   /** @brief Convert's the user's latency preference to samples.
+    * 
+    * Internally, we use number of samples instead of milliseconds as that's
+    * just a preference based on what unit the user wants shown.
+    * 
+    * @return Returns the converted latency preference.
+    * 
+   */
+   long GetConvertedLatencyPreference();
 
    bool                mUpdateMeters;
    volatile bool       mUpdatingMeters;

src/prefs/DevicePrefs.cpp

@@ -411,6 +411,34 @@ bool DevicePrefs::Commit()
       audioIO->StopStream();
    }
 
+   double latency = AudioIOLatencyDuration.Read();
+   bool isMilliseconds = AudioIOLatencyUnit.Read() == "milliseconds";
+
+   // If in milliseconds, convert the latency to samples
+   if (isMilliseconds)
+   {
+      latency *= QualitySettings::DefaultSampleRate.Read() / 1000;
+   }
+
+   // The minimum latency setting is limited to either 32 samples or an
+   // equivalent time in milliseconds at the current sample rate. If the
+   // preference is below this setting, automatically set it to either 32
+   // samples or the equivalent time in milliseconds.
+   //
+   // Why limit the preference to 32 samples? No reason, except it's a pretty
+   // small value already :)
+   if (static_cast<int>(latency) < 32)
+   {
+      latency = 32.0;
+
+      if (isMilliseconds)
+      {
+         latency /= QualitySettings::DefaultSampleRate.Read() / 1000;
+      }
+
+      AudioIOLatencyDuration.Write(latency);
+   }
+
    AudioIO::Get()->UpdateBuffers();
 
    if (monitoring)