examples: Added audio/04-multiple-streams

examples/CMakeLists.txt

@@ -139,6 +139,7 @@ add_sdl_example_executable(renderer-debug-text SOURCES renderer/18-debug-text/de
 add_sdl_example_executable(audio-simple-playback SOURCES audio/01-simple-playback/simple-playback.c)
 add_sdl_example_executable(audio-simple-playback-callback SOURCES audio/02-simple-playback-callback/simple-playback-callback.c)
 add_sdl_example_executable(audio-load-wav SOURCES audio/03-load-wav/load-wav.c DATAFILES ${CMAKE_CURRENT_SOURCE_DIR}/../test/sample.wav)
+add_sdl_example_executable(audio-multiple-streams SOURCES audio/04-multiple-streams/multiple-streams.c)
 add_sdl_example_executable(camera-read-and-draw SOURCES camera/01-read-and-draw/read-and-draw.c)
 add_sdl_example_executable(pen-drawing-lines SOURCES pen/01-drawing-lines/drawing-lines.c)
 add_sdl_example_executable(demo-snake SOURCES demo/01-snake/snake.c)

examples/audio/04-multiple-streams/README.txt

@@ -0,0 +1,5 @@
+This example code loads .wav files dropped onto the app window, puts
+them in an audio stream and binds them for playback. This shows several
+streams mixing into a single playback device.
+
+Drag several files while one is still playing!

examples/audio/04-multiple-streams/multiple-streams.c

@@ -0,0 +1,151 @@
+/*
+ * This example code loads .wav files dropped onto the app window, puts
+ * them in an audio stream and binds them for playback. This shows several
+ * streams mixing into a single playback device.
+ *
+ * This code is public domain. Feel free to use it for any purpose!
+ */
+
+#define SDL_MAIN_USE_CALLBACKS 1  /* use the callbacks instead of main() */
+#include <SDL3/SDL.h>
+#include <SDL3/SDL_main.h>
+
+/* We will use this renderer to draw into this window every frame. */
+static SDL_Window *window = NULL;
+static SDL_Renderer *renderer = NULL;
+static SDL_AudioDeviceID audio_device = 0;
+static SDL_AudioStream **streams = NULL;
+static int num_streams = 0;
+
+/* This function runs once at startup. */
+SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
+{
+    SDL_SetAppMetadata("Example Audio Multiple Streams", "1.0", "com.example.audio-multiple-streams");
+
+    if (!SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO)) {
+        SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
+        return SDL_APP_FAILURE;
+    }
+
+    if (!SDL_CreateWindowAndRenderer("examples/audio/multiple-streams", 640, 480, 0, &window, &renderer)) {
+        SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
+        return SDL_APP_FAILURE;
+    }
+
+    /* open the default audio device in whatever format it prefers; our audio streams will adjust to it. */
+    audio_device = SDL_OpenAudioDevice(SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK, NULL);
+    if (audio_device == 0) {
+        SDL_Log("Couldn't open audio device: %s", SDL_GetError());
+        return SDL_APP_FAILURE;
+    }
+
+    return SDL_APP_CONTINUE;  /* carry on with the program! */
+}
+
+static void load_wav_file(const char *fname)
+{
+    int idx;
+    SDL_AudioSpec spec;
+    Uint8 *wav_data = NULL;
+    Uint32 wav_data_len = 0;
+
+    /* Find an unused element in the streams array... */
+    for (idx = 0; idx < num_streams; idx++) {
+        if (streams[idx] == NULL) {
+            break;
+        }
+    }
+
+    /* No space? Grow the array. */
+    if (idx == num_streams) {
+        void *ptr = SDL_realloc(streams, (num_streams + 1) * sizeof (*streams));
+        if (!ptr) {
+            SDL_Log("Out of memory!");
+            return;  // oh well.
+        }
+        streams = (SDL_AudioStream **) ptr;
+        streams[idx] = NULL;
+        num_streams++;
+    }
+
+    /* Load the new .wav file */
+    if (!SDL_LoadWAV(fname, &spec, &wav_data, &wav_data_len)) {
+        SDL_Log("Failed to load '%s': %s", fname, SDL_GetError());
+        return;  // oh well.
+    }
+
+    /* Create an audio stream. Set the source format to the wav's format (what
+       we'll input), leave the dest format NULL here (it'll change to what the
+       device wants once we bind it). */
+    streams[idx] = SDL_CreateAudioStream(&spec, NULL);
+    if (!streams[idx]) {
+        SDL_Log("Couldn't create audio stream: %s", SDL_GetError());
+    } else if (!SDL_BindAudioStream(audio_device, streams[idx])) {  /* once bound, it'll start playing when there is data available! */
+        SDL_Log("Failed to bind '%s' stream to device: %s", fname, SDL_GetError());
+    } else if (!SDL_PutAudioStreamData(streams[idx], wav_data, (int) wav_data_len)) {
+        SDL_Log("Failed to put '%s' data into stream: %s", fname, SDL_GetError());
+    } else {
+        /* tell SDL we won't be sending more data to this stream, so don't hold back for resampling. */
+        SDL_FlushAudioStream(streams[idx]);
+    }
+
+    SDL_free(wav_data);
+}
+
+/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
+SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
+{
+    if (event->type == SDL_EVENT_QUIT) {
+        return SDL_APP_SUCCESS;  /* end the program, reporting success to the OS. */
+    } else if (event->type == SDL_EVENT_DROP_FILE) {
+        load_wav_file(event->drop.data);
+    }
+    return SDL_APP_CONTINUE;  /* carry on with the program! */
+}
+
+/* This function runs once per frame, and is the heart of the program. */
+SDL_AppResult SDL_AppIterate(void *appstate)
+{
+    int winw = 640, winh = 480;
+    const char *text = "--> Drag and drop .wav files here <--";
+    float x, y;
+    int i;
+
+    /* see if any streams have finished; destroy them if so. */
+    for (i = 0; i < num_streams; i++) {
+        if (streams[i] && (SDL_GetAudioStreamAvailable(streams[i]) == 0)) {
+            SDL_DestroyAudioStream(streams[i]);
+            streams[i] = NULL;
+        }
+    }
+
+    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
+    SDL_RenderClear(renderer);
+    SDL_GetWindowSize(window, &winw, &winh);
+    x = (((float) winw) - (SDL_strlen(text) * SDL_DEBUG_TEXT_FONT_CHARACTER_SIZE)) / 2.0f;
+    y = (((float) winh) - SDL_DEBUG_TEXT_FONT_CHARACTER_SIZE) / 2.0f;
+    SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
+    SDL_RenderDebugText(renderer, x, y, text);
+    SDL_RenderPresent(renderer);
+
+    return SDL_APP_CONTINUE;  /* carry on with the program! */
+}
+
+/* This function runs once at shutdown. */
+void SDL_AppQuit(void *appstate, SDL_AppResult result)
+{
+    int i;
+
+    SDL_CloseAudioDevice(audio_device);
+
+    /* see if any streams have finished; destroy them if so. */
+    for (i = 0; i < num_streams; i++) {
+        if (streams[i]) {
+            SDL_DestroyAudioStream(streams[i]);
+        }
+    }
+
+    SDL_free(streams);
+
+    /* SDL will clean up the window/renderer for us. */
+}