play-manual-square-wave-instead-of-file (#2)

Remove dependency on external raw audio file.\
Play manual square wave instead.

Reviewed-on: #2
Co-authored-by: bjoernf <bjoern.foersterling@web.de>
Co-committed-by: bjoernf <bjoern.foersterling@web.de>

.gitignore

@@ -1 +1,2 @@
 a.out
+tags

README.md

@@ -1,17 +1,16 @@
+## countdown
+
 Simple command line countdown timer that plays a sound when the time is up.
 
-It is using `pulseaudio`s simple API.
+When the time has expired a square wave is sent to `pulseaudio`s simple API \
+to notify the user.
 
 #### installation
 
-install `libpulse-dev` (debian based) or `libpulse` package depending on your distro
+Install `libpulse-dev` (debian based) or `libpulse` package depending on your distribution.
 
 ```
-sudo pacman -S libpulse pulseaudio sound-theme-freedesktop
+sudo pacman -S libpulse pulseaudio
-```
-
-```
-ffmpeg -i /usr/share/sounds/freedesktop/stereo/alarm-clock-elapsed.oga ${HOME}/music/alarm-clock-elapsed.wav
 ```
 
 ```
@@ -23,6 +22,7 @@ sudo make install
 
 #### usage
 
+Start a 20 minute countdown:
 ```
 countdown 20
 ```
@@ -35,5 +35,4 @@ sudo make uninstall
 
 #### TODO
 
-- make alarm clock file wave file configurable
+- Arch Linux package
-- fix still reachable bytes (still reachable: 42,485 bytes in 97 blocks)?

main.c

@@ -1,9 +1,9 @@
 #include "play_raw_audio.h"
 #include <stdio.h>
 #include <stdlib.h>
-#include <unistd.h>
-#include <time.h>
 #include <string.h>
+#include <time.h>
+#include <unistd.h>
 
 // debug pulse audio problems
 #define PA_DEBUG 0
@@ -59,7 +59,8 @@ int main(int argc, char **argv) {
 	}
 
 	printf ("THE TIME IS UP!\n");
-	play_raw_audio(audio_file_path);
+	
+	play_manual_alarm();
 
 	return 0;
 }

makefile

@@ -1,6 +1,6 @@
 .PHONY:all
 all:
-	gcc -Wall *.c -lpulse-simple
+	gcc -Wall *.c -lpulse-simple -lpulse
 
 .PHONY:run
 run:

play_raw_audio.c

@@ -1,4 +1,5 @@
 #include "play_raw_audio.h"
+#include "time_utils.h"
 #include <errno.h>
 #include <fcntl.h>
 #include <pulse/error.h>
@@ -7,6 +8,27 @@
 #include <string.h>
 #include <unistd.h>
 
+// prototypes for static functions
+static int play_square_wave(float frequency, float duration);
+
+int play_manual_alarm() {
+	int err = 0;
+
+	for (int i = 0; i < 3; i++) {
+		for (int i = 0; i < 2; i++) {
+			err = play_square_wave(1000.0, 0.2);
+			if (err != 0) {
+				return err;
+			}
+			sleep_ms(200);
+		}
+		sleep_ms(500);
+	}
+	return 0;
+}
+
+// UNUSED
+// Playing a raw audio file has the downside of depending on a file.
 int play_raw_audio(char file_name[]) {
 	int pa_error = 0;
 	char content[1024] = "";
@@ -42,3 +64,54 @@ int play_raw_audio(char file_name[]) {
 
 	return 0;
 }
+
+// Output a tone with the audio frequency "frequency"
+// for "duration" number of seconds.
+// The sound signals are not sine waves but square waves.
+static int play_square_wave(float frequency, float duration) {
+	const int sample_rate = 44100;
+	const int channel_count = 2;
+	size_t buffer_size = sample_rate * channel_count * duration;
+	short buffer[buffer_size] = {};
+	pa_simple *s;
+
+	pa_sample_spec ss = {
+		.format = PA_SAMPLE_S16LE,
+		.rate = sample_rate,
+		.channels = channel_count,
+	};
+
+	// number of identical consecutive elements
+	// 5 would look like this:
+	// [0,0,0,0,0,32768,32768,32768,32768,32768,0,...]
+	int array_interval = sample_rate / frequency;
+
+	bool square_peak = false;
+	for (int i = 0; i < buffer_size; i++) {
+		if (i % array_interval == 0) {
+			// toggle the value (0 or the max value for a short)
+			square_peak = !square_peak;
+		}
+		if (square_peak) {
+			buffer[i] = SHRT_MAX;
+		} else {
+			buffer[i] = 0;
+		}
+	}
+
+	if (!(s = pa_simple_new(NULL, NULL, PA_STREAM_PLAYBACK, NULL, "playback", &ss, NULL, NULL, &errno))) {
+		fprintf(stderr, "pa_simple_new() failed: %s\n", pa_strerror(errno));
+		return 1;
+	}
+
+	if (pa_simple_write(s, buffer, sizeof(buffer), NULL) < 0) {
+		fprintf(stderr, "pa_simple_write() failed: %s\n", pa_strerror(errno));
+		return 1;
+	}
+
+	pa_simple_drain(s, NULL);
+
+	pa_simple_free(s);
+
+	return 0;
+}

play_raw_audio.h

@@ -1,3 +1,4 @@
 #pragma once
 
+int play_manual_alarm();
 int play_raw_audio(char file_name[]);

time_utils.c

@@ -0,0 +1,10 @@
+#include <time.h>
+
+void sleep_ms(int milliseconds) {
+	struct timespec ts = {
+		.tv_sec = 0,
+		.tv_nsec = milliseconds * 1e6,
+	};
+
+	nanosleep(&ts, NULL);
+}

time_utils.h

@@ -0,0 +1,3 @@
+#pragma once
+
+void sleep_ms(int milliseconds);