Initialize sample rate and block size of RtAudioDevice in constructor instead of openStream(). Fix algorithm to find closest allowed sample rate of device.

src/rtaudio.cpp

@@ -40,13 +40,21 @@ struct RtAudioDevice : audio::Device {
 	RtAudio::StreamParameters inputParameters;
 	RtAudio::StreamParameters outputParameters;
 	RtAudio::StreamOptions options;
-	int blockSize = 0;
-	float sampleRate = 0;
+	int blockSize;
+	float sampleRate;
 
 	RtAudioDevice(RtAudio::Api api, int deviceId) {
 		this->api = api;
 		this->deviceId = deviceId;
 
+		sampleRate = 44100;
+
+		// DirectSound latency is too high for 256 block size.
+		if (api == RtAudio::WINDOWS_DS)
+			blockSize = 1024;
+		else
+			blockSize = 256;
+
 		// Create RtAudio object
 		INFO("Creating RtAudio %s context", RTAUDIO_API_NAMES.at(api).c_str());
 		try {
@@ -102,25 +110,14 @@ struct RtAudioDevice : audio::Device {
 		options.numberOfBuffers = 2;
 		options.streamName = "VCV Rack";
 
-		// Most people prefer 44100 default sample rate although many devices report 48000 from `deviceInfo.preferredSampleRate`.
-		float closestSampleRate = 44100;
-		if (sampleRate > 0) {
-			// Find the closest sample rate to the requested one.
-			for (float sr : deviceInfo.sampleRates) {
-				if (std::fabs(sr - sampleRate) < std::fabs(closestSampleRate - sampleRate)) {
-					closestSampleRate = sr;
-				}
+		float closestSampleRate = INFINITY;
+		// Find the closest sample rate to the requested one.
+		for (float sr : deviceInfo.sampleRates) {
+			if (std::fabs(sr - sampleRate) < std::fabs(closestSampleRate - sampleRate)) {
+				closestSampleRate = sr;
 			}
 		}
 
-		if (blockSize <= 0) {
-			// DirectSound should use a higher default block size
-			if (api == RtAudio::WINDOWS_DS)
-				blockSize = 1024;
-			else
-				blockSize = 256;
-		}
-
 		INFO("Opening RtAudio %s device %d: %s (%d in, %d out, %g sample rate, %d block size)", RTAUDIO_API_NAMES.at(api).c_str(), deviceId, deviceInfo.name.c_str(), inputParameters.nChannels, outputParameters.nChannels, closestSampleRate, blockSize);
 		try {
 			rtAudio->openStream(