SFML Sound not playing (Operation not permitted) - c++

Question

So I was trying out the SFML tutorial for playing a sound from a local file and came across a weird bug. Whenever I call the playSound function no sound is played and I get an error that I can't find the solution to:
[ALSOFT] (EE) Failed to set real-time priority for thread: Operation not permitted (1)
The strange thing is that if I do the same thing in the main function the sound is played. What is going on here? Here are the only files used in the project, the .wav is just a simple sound file:
main.cpp
#include <SFML/Graphics.hpp>
#include <SFML/Audio.hpp>
void playSound() {
sf::SoundBuffer buffer;
if (!buffer.loadFromFile("1-retro-arcade-casino-notification.wav"))
return;
sf::Sound sound;
sound.setBuffer(buffer);
sound.play();
}
int main() {
sf::RenderWindow window(sf::VideoMode(800, 600), "Notification test");
sf::SoundBuffer buffer;
if (!buffer.loadFromFile("1-retro-arcade-casino-notification.wav"))
return -1;
sf::Sound sound;
sound.setBuffer(buffer);
sound.play();
while (window.isOpen()) {
sf::Event event;
while (window.pollEvent(event)) {
if (event.type == sf::Event::Closed) {
window.close();
}
if (event.type == sf::Event::TextEntered) {
char key = static_cast<char>(event.text.unicode);
if (key == 'p') {
playSound();
}
if (key == 'q') {
window.close();
}
}
}
}
return 0;
}
Makefile
all:
g++ -lsfml-audio -lsfml-graphics -lsfml-window -lsfml-system -o main main.cpp

Answer 1

The sound data is not stored directly in sf::Sound but instead in the sf::SoundBuffer. This class encapsulates the audio data, which is basically an array of 16-bit signed integers (called "audio samples").
Sounds (and music) are played in a separate thread. This means that you are free to do anything you want after calling
void play(), except destroying the sound or its data - which you are currently doing.
This is because you have declared your sf::SoundBuffer buffer; inside void playSound(), and subsequently, the sound data gets destroyed as it goes out of scope after returning from void playSound().
To fix your problem, don't declare sf::SoundBuffer in the function. You could just declare it outside the main function, or even pass it as a parameter to playSound().
See the relevant documentation for info.