comparison examples/04-Audio/samples/render.cpp @ 464:8fcfbfb32aa0 prerelease

Examples reorder with subdirectories. Added header to each project. Moved Doxygen to bottom of render.cpp.

+/*
+ ____  _____ _        _    
+| __ )| ____| |      / \   
+|  _ \|  _| | |     / _ \  
+| |_) | |___| |___ / ___ \ 
+|____/|_____|_____/_/   \_\
+
+The platform for ultra-low latency audio and sensor processing
+
+http://bela.io
+
+A project of the Augmented Instruments Laboratory within the
+Centre for Digital Music at Queen Mary University of London.
+http://www.eecs.qmul.ac.uk/~andrewm
+
+(c) 2016 Augmented Instruments Laboratory: Andrew McPherson,
+  Astrid Bin, Liam Donovan, Christian Heinrichs, Robert Jack,
+  Giulio Moro, Laurel Pardue, Victor Zappi. All rights reserved.
+
+The Bela software is distributed under the GNU Lesser General Public License
+(LGPL 3.0), available here: https://www.gnu.org/licenses/lgpl-3.0.txt
+*/
+
+
+#include <Bela.h>
+#include <cmath>
+#include "SampleData.h"
+
+SampleData gSampleData;	// User defined structure to get complex data from main
+int gReadPtr;			// Position of last read sample from file
+
+// Task for handling the update of the frequencies using the matrix
+AuxiliaryTask gTriggerSamplesTask;
+
+bool initialise_trigger();
+void trigger_samples();
+
+bool setup(BelaContext *context, void *userData)
+{
+
+	// Retrieve a parameter passed in from the initAudio() call
+	gSampleData = *(SampleData *)userData;
+
+	gReadPtr = -1;
+
+	// Initialise auxiliary tasks
+	if(!initialise_trigger())
+		return false;
+
+	return true;
+}
+
+void render(BelaContext *context, void *userData)
+{
+	for(unsigned int n = 0; n < context->audioFrames; n++) {
+		float out = 0;
+
+		// If triggered...
+		if(gReadPtr != -1)
+			out += gSampleData.samples[gReadPtr++];	// ...read each sample...
+
+		if(gReadPtr >= gSampleData.sampleLen)
+			gReadPtr = -1;
+
+		for(unsigned int channel = 0; channel < context->audioChannels; channel++)
+			context->audioOut[n * context->audioChannels + channel] = out;	// ...and put it in both left and right channel
+	}
+
+	// Request that the lower-priority task run at next opportunity
+	Bela_scheduleAuxiliaryTask(gTriggerSamplesTask);
+}
+
+// Initialise the auxiliary task
+// and print info
+
+bool initialise_trigger()
+{
+	if((gTriggerSamplesTask = Bela_createAuxiliaryTask(&trigger_samples, 50, "bela-trigger-samples")) == 0)
+		return false;
+
+	rt_printf("Press 'a' to trigger sample, 's' to stop\n");
+	rt_printf("Press 'q' to quit\n");
+
+	return true;
+}
+
+// This is a lower-priority call to periodically read keyboard input
+// and trigger samples. By placing it at a lower priority,
+// it has minimal effect on the audio performance but it will take longer to
+// complete if the system is under heavy audio load.
+
+void trigger_samples()
+{
+	// This is not a real-time task!
+	// Cos getchar is a system call, not handled by Xenomai.
+	// This task will be automatically down graded.
+
+	char keyStroke = '.';
+
+	keyStroke =	getchar();
+	while(getchar()!='\n'); // to read the first stroke
+
+	switch (keyStroke)
+	{
+		case 'a':
+			gReadPtr = 0;
+			break;
+		case 's':
+			gReadPtr = -1;
+			break;
+		case 'q':
+			gShouldStop = true;
+			break;
+		default:
+			break;
+	}
+}
+
+
+void cleanup(BelaContext *context, void *userData)
+{
+	delete[] gSampleData.samples;
+}
+
+/* ------------ Project Explantation ------------ */
+
+/**
+\example 04-samples
+
+Playback WAV files
+------------------
+
+This sketch shows how to playback audio samples from a buffer.
+
+An audio file is loaded into a buffer `SampleData` as `gSampleData`. This is 
+accessed with a read pointer that is incremented at audio rate within the render 
+function: `out += gSampleData.samples[gReadPtr++]`.
+
+Note that the read pointer is stopped from incrementing past the length of the 
+`gSampleData`. This is achieved by comparing the read pointer value against the 
+sample length which we can access as follows: `gSampleData.sampleLen`.
+
+The sample is triggered by keyboard input: (a) starts sample playback, (s) 
+stops sample playback. The triggering is treated as a lower priority task than 
+the audio. You can see this at the bottom of the render function: 
+`Bela_scheduleAuxiliaryTask(gTriggerSamplesTask)`;
+*/