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rishi_tank

Using sound with SDL_Mixer in C++

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Hi there, i am currently new to C++ and was using the lazyfoo tutorials to learn how to use the SDL library. I am trying to make a game, and i followed everything in the LazyFoo tutorials on how to get music into my game using SDL_Mixer.h but when compiling my code the window appears for a second with a black screen and then disappears lol. I was hoping someone on here could possible fix my problem or guide me in the right direction? My code in my main.cpp file is as follows: // The headers #include "SDL.h" #include "SDL_image.h" #include "SDL_ttf.h" #include "SDL_mixer.h" #include "timer.h" #include "screen.h" #include "image.h" #include "player.h" #include "animation.h" #include <string> #include <sstream> #include <vector> using namespace std; // The surfaces that will be used SDL_Surface *background = NULL; SDL_Surface *facingR = NULL; SDL_Surface *facingL = NULL; SDL_Surface *defaultFace = NULL; Mix_Music *music = NULL; // Make the shapes Player player_one, other; // Function prototypes bool init(); bool load_files(); void clean_up(); void Player::show() { if(player_one.velocityX >= 0 && stopWalkingRight == true) { // Show the player apply_surface(box.x - camera.x, box.y - camera.y, facingR, screen, 0); } else if(player_one.velocityX <= 0 && stopWalkingLeft == true) { // Show the player apply_surface(box.x - camera.x, box.y - camera.y, facingL, screen, 0); } else { // Show the player apply_surface(box.x - camera.x, box.y - camera.y, defaultFace, screen, 0); } } int main(int argc, char* args[]) { // Quit flag bool quit = false; // Keep track of the current frame int frame = 0; // Initialise if(init() == false) { return 1; } // Load the files if(load_files() == false) { return 1; } // Start the update timer update.start(); // Start the frame timer fps.start(); /*vector<SDL_Rect> box(1); Circle other;*/ // Set shapes' attributes /*box[0].x = 60; box[0].y = 60; box[0].w = 40; box[0].h = 40; other.x = 30; other.y = 30; other.r = PLAYER_WIDTH/2;*/ // Set the wall wall[0].x = 300; wall[0].y = 40; wall[0].w = 40; wall[0].h = 400; // Set the sprite sheet clips set_clips(); // Make the sprite Ani walk; // While the user hasn't quit while(quit == false) { // While there's events to handle while(SDL_PollEvent(&event)) { // Handle events for the player player_one.handle_input(); // Handle events for the sprite walk.handle_events(); // If a key was pressed if(event.type == SDL_KEYDOWN) { // If Space was pressed if(event.key.keysym.sym == SDLK_SPACE) { // If there is no music playing if(Mix_PlayingMusic() == 0) { // Play the music if(Mix_PlayMusic(music, 0) == -1) { return 1; } } // If the music is being played else { // If the music is paused if(Mix_PausedMusic() == 1) { // Resume the music Mix_ResumeMusic(); } // If the music is playing else { // Pause the music Mix_PauseMusic(); } } } // If 0 was pressed else if(event.key.keysym.sym == SDLK_0) { // Stop the music Mix_HaltMusic(); } // If escape was pressed else if(event.key.keysym.sym == SDLK_ESCAPE) { quit = true; } } // If the user has closed the window if(event.type == SDL_QUIT) { // Quit the program quit = true; } } /*if(player_one.getYpos() == 150) { player_one.jumping = false; } if(player_one.jumping == false) { if(player_one.getYpos() < (LEVEL_HEIGHT - PLAYER_HEIGHT)) { while(player_one.velocityY < 5) { player_one.velocityY += ACCEL; player_one.jumping = false; } } else { player_one.velocityY = 0; } }*/ // Move the sprite walk.move(); // Set the camera player_one.set_camera(); // Move the dot player_one.move(); // Apply the background apply_surface(0, 0, background, screen, &camera); //Show the box /*SDL_FillRect(screen, &box[0], SDL_MapRGB(screen->format, 0x00, 0x00, 0x00));*/ //Show the wall /*SDL_FillRect(screen, &wall[0], SDL_MapRGB(screen->format, 0x77, 0x77, 0x77));*/ // Show other player /*apply_surface(other.getXpos() - other.getRpos(), other.getYpos() - other.getRpos(), player, screen, 0);*/ // Show the dot on the screen player_one.show(); // Show the sprite on the screen /*walk.show();*/ // Update the screen if(SDL_Flip(screen) == -1) { return 1; } // Increment the frame counter frame++; // Cap the frame rate while(fps.get_ticks() < 1000/FRAMES_PER_SECOND) { SDL_Delay((1000/FRAMES_PER_SECOND) - fps.get_ticks()); } // If a second has passed since the caption was last updated if(update.get_ticks() > 1000) { // The frame rate as a string stringstream caption; // Calculate the frames per second and create the string caption << "My Game | FPS: " << frame / (fps.get_ticks() / 1000.f) << " Velocity: " << player_one.getVelY() << " Offset X: " << player_one.getYpos(); // Reset the caption SDL_WM_SetCaption(caption.str().c_str(), ""); // Restart the update timer update.start(); } } // Free the surface and quit SDL clean_up(); // If everything went ok return 0; } bool init() { // Initialise all SDL subsystems if(SDL_Init(SDL_INIT_EVERYTHING) == -1) { return false; } // Set up the screen screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_SWSURFACE); // If there was an error in setting up the screen if(screen == NULL) { return false; } // Initialise SDL_mixer if(Mix_OpenAudio(22050, MIX_DEFAULT_FORMAT, 2, 4096) == -1) { return false; } // Set the window caption SDL_WM_SetCaption("My Game", ""); // If everything initialises fine return true; } bool load_files() { // Load the image background = load_image("background1.jpg"); ani = load_image("walking.png"); // If there was an error in loading the image if(background == NULL) { return false; } facingL = load_image("character_facingL.gif"); facingR = load_image("character_facingR.gif"); defaultFace = facingR; if(facingL == NULL || facingR == NULL) { return false; } // Load the music music = Mix_LoadMUS("beat.wav"); // If there was a problem loading the music if(music == NULL) { return false; } // If everything loaded successfully return true; } void clean_up() { // Free the image SDL_FreeSurface(background); // Free the player SDL_FreeSurface(facingL); SDL_FreeSurface(facingR); SDL_FreeSurface(ani); // Free the sound effects Mix_CloseAudio(); // Quit SDL SDL_Quit(); } Thanks!

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Firstly, when you're posting code (on almost any forum) use the [ code ] [ /code ] tags i.e.:

SDL_Surface *background = NULL;


As far as pointing you in the right direction:
Debugging is an essential skill for any programmer to have, even if you're only planning on making programming a hobby.

Presumably you're using an IDE (Integrated Development Environment), something like Visual Studio or DevC++ or CodeBlocks.

All of these have a 'debug' mode, which allows you step through your code one line at a time.
This enables you to see what lines of code are working and what lines are not.

If you're feeling lazy you can also just launch debug mode, put a breakpoint at the beginning of your program, then run it from there and wait for the crash - debug mode will usually log the callstack of your app so you can see what was happening just before the crash and that will give you an idea.

Aside from using debug mode, another useful tool when debugging is using COUT and/or CERR to output something whenever an error occurs.
CERR is used for errors, COUT is a general purpose type thing.

in your code you've got statements like:

if(Mix_OpenAudio(22050, MIX_DEFAULT_FORMAT, 2, 4096) == -1) {
return false;
}


so that's saying "If Mix_Audio was unable to open the audio output device, close the program"
to make this easier to debug, every time you return a value which will cause your application to close, do something like this:

if(Mix_OpenAudio(22050, MIX_DEFAULT_FORMAT, 2, 4096) == -1)
{
cerr << "Unable to open audio device. Mix_GetError: " << Mix_GetError() << endl;
return false;
}


because you're using SDL this will result in a text file being created called cerr.txt, and inside that you'll find the line "Unable to open audio device. Mix_GetError: qwerty".

To achieve the same thing in debug mod you'd set a breakpoint on every "return false;" statement you have in your init code (and anywhere else you do it that would cause the program to exit) and then run the program in debug mode.
Whenever one of those lines is executed the program will stop and you'll be able to see what's failing.

A good reason for using CERR/COUT is because presumably you're going to be building this as an exe one day, so when you distribute it to whoever and it crashes, you'll be able to get them to send you the error log to see what's going on.

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