basic audio streaming

audio.c

// macOS

// CFLAGS += -ObjC
// LDFLAGS += -framework Cocoa -framework OpenGL -framework AudioToolbox

#define GL_SILENCE_DEPRECATION 1
#import <Cocoa/Cocoa.h>
#include <OpenGL/gl.h>
#include <AudioToolbox/AudioToolbox.h>

#define BUFFER_FRAMES 1024
#define SAMPLE_RATE 44100
#define NUM_CHANNELS 1

int t = 0;
int freq = 440;
float volume = 0.3;

static void stream_audio(void *udata, AudioQueueRef queue, AudioQueueBufferRef buffer) {

	int num_frames = buffer->mAudioDataByteSize / (sizeof(float) * NUM_CHANNELS);
	float *data = (float*)buffer->mAudioData;

	for (int i = 0; i < num_frames; i++) {
		t++;
		data[i] = sin((float)t / SAMPLE_RATE * freq * 2.0 * 3.14) * volume;
	}

	AudioQueueEnqueueBuffer(queue, buffer, 0, NULL);

}

int main() {

	[NSApplication sharedApplication];
	[NSApp setActivationPolicy:NSApplicationActivationPolicyRegular];
	[NSApp activateIgnoringOtherApps:YES];

	NSWindow *window = [[NSWindow alloc]
		initWithContentRect:NSMakeRect(0, 0, 400, 400)
		styleMask:
			0
			| NSWindowStyleMaskTitled
			| NSWindowStyleMaskClosable
			| NSWindowStyleMaskResizable
			| NSWindowStyleMaskMiniaturizable
		backing:NSBackingStoreBuffered
		defer:NO
	];

	NSOpenGLView *view = [[NSOpenGLView alloc] init];
	[window setContentView:view];
	[window makeFirstResponder:view];

	[window setTitle:@"hi"];
	[window center];
	[window makeKeyAndOrderFront:nil];

	NSOpenGLContext *ctx = [view openGLContext];

	[ctx makeCurrentContext];

	AudioStreamBasicDescription fmt = {
		.mSampleRate = SAMPLE_RATE,
		.mFormatID = kAudioFormatLinearPCM,
		.mFormatFlags = 0
			| kLinearPCMFormatFlagIsFloat
			| kAudioFormatFlagIsPacked
			,
		.mFramesPerPacket = 1,
		.mChannelsPerFrame = NUM_CHANNELS,
		.mBytesPerFrame = sizeof(float) * NUM_CHANNELS,
		.mBytesPerPacket = sizeof(float) * NUM_CHANNELS,
		.mBitsPerChannel = 32,
	};

	AudioQueueRef queue;

	AudioQueueNewOutput(
		&fmt,
		stream_audio,
		NULL,
		NULL,
		NULL,
		0,
		&queue
	);

	for (int i = 0; i < 2; i++) {

		int buf_size = BUFFER_FRAMES * fmt.mBytesPerFrame;
		AudioQueueBufferRef buf;

		AudioQueueAllocateBuffer(queue, buf_size, &buf);
		buf->mAudioDataByteSize = buf_size;
		memset(buf->mAudioData, 0, buf->mAudioDataByteSize);

		AudioQueueEnqueueBuffer(queue, buf, 0, NULL);

	}

	AudioQueueStart(queue, NULL);

	while (1) {

		while (1) {

			NSEvent *event = [NSApp
				nextEventMatchingMask:NSEventMaskAny
				untilDate:[NSDate distantPast]
				inMode:NSDefaultRunLoopMode
				dequeue:YES
			];

			if (event == nil) {
				break;
			}

			switch (event.type) {
				case NSEventTypeKeyDown:
					break;
				default:
					break;
			}

			[NSApp sendEvent:event];

		}

		NSPoint mpos = [window mouseLocationOutsideOfEventStream];

		if (mpos.x > 200.0 && mpos.x < 400.0) {
			freq = (int)mpos.x * 2;
		}

		glClearColor(0, mpos.x / 400, mpos.y / 400, 1);
		glClear(GL_COLOR_BUFFER_BIT);
		glFlush();

	}

}