comparison core/RTAudio.cpp @ 178:a156a694864d

-p flag now indicates the buffer size in audio samples. Closes #1520

 // User data passed in from main()
 void *gUserData;
 
 // initAudio() prepares the infrastructure for running PRU-based real-time
 // audio, but does not actually start the calculations.
-// periodSize indicates the number of _sensor_ frames per period: the audio period size
-// is twice this value. In total, the audio latency in frames will be 4*periodSize,
+// periodSize indicates the number of audio frames per period: the analog period size
+// will depend on the number of analog channels, in such a way that
+// analogPeriodSize = 4*periodSize/numAnalogChannels
+// In total, the audio latency in frames will be 2*periodSize,
 // plus any latency inherent in the ADCs and DACs themselves.
 // useAnalog indicates whether to enable the ADC and DAC or just use the audio codec.
 // numAnalogChannels indicates how many ADC and DAC channels to use.
 // userData is an opaque pointer which will be passed through to the setup()
 // function for application-specific use

 	else if(settings->numAnalogChannels >= 4)
 		settings->numAnalogChannels = 4;
 	else
 		settings->numAnalogChannels = 2;
 
-	// Sanity check the combination of channels and period size
-	if(settings->numAnalogChannels <= 4 && settings->periodSize < 2) {
-		cout << "Error: " << settings->numAnalogChannels << " channels and period size of " << settings->periodSize << " not supported.\n";
-		return 1;
-	}
-	if(settings->numAnalogChannels <= 2 && settings->periodSize < 4) {
-		cout << "Error: " << settings->numAnalogChannels << " channels and period size of " << settings->periodSize << " not supported.\n";
-		return 1;
-	}
-
 	// Initialise the rendering environment: sample rates, frame counts, numbers of channels
 	gContext.audioSampleRate = 44100.0;
 	gContext.audioChannels = 2;
 
 	if(settings->useAnalog) {
-		gContext.audioFrames = settings->periodSize * settings->numAnalogChannels / 4;
-
-		gContext.analogFrames = settings->periodSize;
+		gContext.audioFrames = settings->periodSize;
+
+		gContext.analogFrames = gContext.audioFrames * 4 / settings->numAnalogChannels;
 		gContext.analogChannels = settings->numAnalogChannels;
 		gContext.analogSampleRate = gContext.audioSampleRate * 4.0 / (float)settings->numAnalogChannels;
 	}
 	else {
-		gContext.audioFrames = settings->periodSize * 2;
+		gContext.audioFrames = settings->periodSize;
 
 		gContext.analogFrames = 0;
 		gContext.analogChannels = 0;
 		gContext.analogSampleRate = 0;
+	}
+
+	// Sanity check the combination of channels and period size
+	if( (gContext.analogChannels <= 4 && gContext.analogFrames < 2) ||
+			(gContext.analogChannels <= 2 && gContext.analogFrames < 4))
+	{
+		cout << "Error: " << gContext.analogChannels << " channels and period size of " << gContext.analogFrames << " not supported.\n";
+		return 1;
 	}
 
 	// For now, digital frame rate is equal to audio frame rate
 	if(settings->useDigital) {
 		gContext.digitalFrames = gContext.audioFrames;

 		cout << "Error: unable to prepare GPIO for PRU audio\n";
 		return 1;
 	}
 
 	// Get the PRU memory buffers ready to go
-	if(gPRU->initialise(0, settings->periodSize, settings->numAnalogChannels, true)) {
+	if(gPRU->initialise(0, gContext.analogFrames, gContext.analogChannels, true)) {
 		cout << "Error: unable to initialise PRU\n";
 		return 1;
 	}
 
 	// Prepare the audio codec, which clocks the whole system