Standalone: persist the requested sample rate, and validate it on an input-only stream

src/detail/standalone/standalone_host.cpp

@@ -474,13 +474,13 @@ bool StandaloneHost::saveStandaloneSettings()
 void StandaloneHost::captureAudioSettings()
 {
   settings.audioApiName = audioApiName;
-  settings.sampleRate = currentSampleRate;
   settings.bufferSize = currentBufferSize;
 
-  // Device names and used flags are deliberately not captured: they describe what
-  // could actually be opened (a fallback device, a side that failed to open), and
-  // saveSettings() runs often enough that persisting them would silently replace
-  // the user's choice. The frontend writes them at the point of choice instead.
+  // Device names, used flags and the sample rate are deliberately not captured:
+  // they describe what could actually be opened (a fallback device, a side that
+  // failed to open, a rate the device does not offer), and saveSettings() runs
+  // often enough that persisting them would silently replace the user's choice.
+  // The frontend writes them at the point of choice instead.
 }
 
 void StandaloneHost::applyAudioSettings()
@@ -526,7 +526,8 @@ void StandaloneHost::applyAudioSettings()
     }
   }
 
-  // The sample rate needs no clamp: startAudioThreadOn() validates it.
+  // The sample rate needs no clamp: startAudioThreadOn() resolves it against the
+  // device it is about to open.
 }
 
 bool StandaloneHost::isKnownDevice(unsigned int deviceID)

src/detail/standalone/standalone_host.h

@@ -149,8 +149,8 @@ struct StandaloneHost : Clap::IHost
   // Current audio configuration -> settings, and back. applyAudioSettings()
   // selects the API and resolves the persisted device *names* against the
   // devices this machine actually has right now.
-  // captureAudioSettings() writes back only the API, sample rate and buffer size;
-  // the device names and used flags are the user's request, written by the frontend.
+  // captureAudioSettings() writes back only the API and buffer size; the device
+  // names, used flags and sample rate are the user's request, written by the frontend.
   void captureAudioSettings();
   void applyAudioSettings();
 

src/detail/standalone/standalone_host_audio.cpp

@@ -21,6 +21,21 @@
 
 namespace freeaudio::clap_wrapper::standalone
 {
+namespace
+{
+// The requested rate if the device offers it, its preferred rate otherwise.
+int32_t rateOfferedBy(const RtAudio::DeviceInfo &info, int32_t requested)
+{
+  if (requested > 0 && std::find(info.sampleRates.begin(), info.sampleRates.end(),
+                                 static_cast<unsigned int>(requested)) != info.sampleRates.end())
+  {
+    return requested;
+  }
+
+  return static_cast<int32_t>(info.preferredSampleRate);
+}
+}  // namespace
+
 int rtaCallback(void *outputBuffer, void *inputBuffer, unsigned int nBufferFrames,
                 double /* streamTime */, RtAudioStreamStatus status, void *data)
 {
@@ -380,23 +395,7 @@ void StandaloneHost::startAudioThreadOnImpl(unsigned int inputDeviceID, uint32_t
     outInfo = deviceInfoFor(outputDeviceID);
     oParams.nChannels = std::min(outputChannels, outInfo.outputChannels);
     oParams.firstChannel = 0;
-    if (sampleRate < 0)
-    {
-      sampleRate = outInfo.preferredSampleRate;
-    }
-    else
-    {
-      // Mkae sure this sample rate is available
-      bool isPossible{false};
-      for (auto sr : outInfo.sampleRates)
-      {
-        isPossible = isPossible || ((int)sr == (int)sampleRate);
-      }
-      if (!isPossible)
-      {
-        sampleRate = outInfo.preferredSampleRate;
-      }
-    }
+    sampleRate = rateOfferedBy(outInfo, sampleRate);
   }
 
   RtAudio::StreamParameters iParams;
@@ -406,10 +405,13 @@ void StandaloneHost::startAudioThreadOnImpl(unsigned int inputDeviceID, uint32_t
     inInfo = deviceInfoFor(inputDeviceID);
     iParams.nChannels = std::min(inputChannels, inInfo.inputChannels);
     iParams.firstChannel = 0;
-    if (sampleRate < 0) sampleRate = inInfo.preferredSampleRate;
+
+    // With no output side nothing else has vetted the rate, and the .conf is
+    // hand-editable; openStream() would simply fail and raise a dialog.
+    if (!useOutput) sampleRate = rateOfferedBy(inInfo, sampleRate);
   }
 
-  if (sampleRate < 0)
+  if (sampleRate <= 0)
   {
     LOGINFO("[WARNING] No preferred sample rate detected; using 48k");
     sampleRate = 48000;

src/detail/standalone/standalone_settings.h

@@ -41,13 +41,13 @@ struct StandaloneSettings
   std::string audioApiName;  // RtAudio::getApiName(); empty means unspecified
 
   // What the user asked for, written only at the point of choice - never from the
-  // device actually opened, which may be a fallback.
+  // device actually opened or the rate actually granted, which may be a fallback.
   std::string inputDeviceName;   // empty means the system default device
   std::string outputDeviceName;  // empty means the system default device
   bool audioInputUsed{true};
   bool audioOutputUsed{true};  // no UI turns this off yet; the .conf can
+  int32_t sampleRate{0};       // 0 means the device's preferred rate
 
-  int32_t sampleRate{0};  // 0 means the device's preferred rate
   // Clamped on apply; see StandaloneHost::applyAudioSettings().
   uint32_t bufferSize{defaultBufferSize};
 

src/detail/standalone/windows/windows_standalone.cpp

@@ -1041,6 +1041,7 @@ Plugin::Plugin(std::shared_ptr<Clap::Plugin> clapPlugin, int nCmdShow)
                             if (auto index{settings.sampleRate.selection(sampleRates.size())}; index)
                             {
                               sah->currentSampleRate = sampleRates[*index];
+                              sah->settings.sampleRate = sampleRates[*index];
 
                               saveSettings();
                               startAudio();
@@ -1370,6 +1371,10 @@ Plugin::Plugin(std::shared_ptr<Clap::Plugin> clapPlugin, int nCmdShow)
 
   startAudio();
 
+  // The rate asked for may have been 0 ("device preferred") or unsupported, so the
+  // combo can only show the truth once the stream is open.
+  refreshSampleRates();
+
   // Honor the show state requested by the launcher (shortcut "Run:" / STARTUPINFO),
   // falling back to a normal window. SW_HIDE would otherwise leave us invisible-but-running.
   ::ShowWindow(hwnd.get(), nCmdShow == SW_HIDE ? SW_SHOWNORMAL : nCmdShow);