Add example for using custom decoders with the resource manager.

research/_examples/custom_decoder_engine.c

+/*
+Demonstrates how to implement a custom decoder.
+
+This example implements two custom decoders:
+
+  * Vorbis via libvorbis
+  * Opus via libopus
+
+A custom decoder must implement a data source. In this example, the libvorbis data source is called
+`ma_libvorbis` and the Opus data source is called `ma_libopus`. These two objects are compatible
+with the `ma_data_source` APIs and can be taken straight from this example and used in real code.
+
+The custom decoding data sources (`ma_libvorbis` and `ma_libopus` in this example) are connected to
+the decoder via the decoder config (`ma_decoder_config`). You need to implement a vtable for each
+of your custom decoders. See `ma_decoding_backend_vtable` for the functions you need to implement.
+The `onInitFile`, `onInitFileW` and `onInitMemory` functions are optional.
+*/
+#define MA_NO_VORBIS    /* Disable the built-in Vorbis decoder to ensure the libvorbis decoder is picked. */
+#define MA_NO_OPUS      /* Disable the (not yet implemented) built-in Opus decoder to ensure the libopus decoder is picked. */
+#define MINIAUDIO_IMPLEMENTATION
+#include "../../miniaudio.h"
+#include "../../extras/miniaudio_libvorbis.h"
+#include "../../extras/miniaudio_libopus.h"
+#include "../miniaudio_engine.h"
+
+#include <stdio.h>
+
+static ma_result ma_decoding_backend_init__libvorbis(void* pUserData, ma_read_proc onRead, ma_seek_proc onSeek, ma_tell_proc onTell, void* pReadSeekTellUserData, const ma_decoding_backend_config* pConfig, const ma_allocation_callbacks* pAllocationCallbacks, ma_data_source** ppBackend)
+{
+    ma_result result;
+    ma_libvorbis* pVorbis;
+
+    (void)pUserData;
+
+    pVorbis = (ma_libvorbis*)ma_malloc(sizeof(*pVorbis), pAllocationCallbacks);
+    if (pVorbis == NULL) {
+        return MA_OUT_OF_MEMORY;
+    }
+
+    result = ma_libvorbis_init(onRead, onSeek, onTell, pReadSeekTellUserData, pConfig, pAllocationCallbacks, pVorbis);
+    if (result != MA_SUCCESS) {
+        return result;
+    }
+
+    *ppBackend = pVorbis;
+
+    return MA_SUCCESS;
+}
+
+static ma_result ma_decoding_backend_init_file__libvorbis(void* pUserData, const char* pFilePath, const ma_decoding_backend_config* pConfig, const ma_allocation_callbacks* pAllocationCallbacks, ma_data_source** ppBackend)
+{
+    ma_result result;
+    ma_libvorbis* pVorbis;
+
+    (void)pUserData;
+
+    pVorbis = (ma_libvorbis*)ma_malloc(sizeof(*pVorbis), pAllocationCallbacks);
+    if (pVorbis == NULL) {
+        return MA_OUT_OF_MEMORY;
+    }
+
+    result = ma_libvorbis_init_file(pFilePath, pConfig, pAllocationCallbacks, pVorbis);
+    if (result != MA_SUCCESS) {
+        return result;
+    }
+
+    *ppBackend = pVorbis;
+
+    return MA_SUCCESS;
+}
+
+static void ma_decoding_backend_uninit__libvorbis(void* pUserData, ma_data_source* pBackend, const ma_allocation_callbacks* pAllocationCallbacks)
+{
+    ma_libvorbis* pVorbis = (ma_libvorbis*)pBackend;
+
+    (void)pUserData;
+
+    ma_libvorbis_uninit(pVorbis, pAllocationCallbacks);
+    ma_free(pVorbis, pAllocationCallbacks);
+}
+
+static ma_result ma_decoding_backend_get_channel_map__libvorbis(void* pUserData, ma_data_source* pBackend, ma_channel* pChannelMap, size_t channelMapCap)
+{
+    ma_libvorbis* pVorbis = (ma_libvorbis*)pBackend;
+
+    (void)pUserData;
+
+    return ma_libvorbis_get_data_format(pVorbis, NULL, NULL, NULL, pChannelMap, channelMapCap);
+}
+
+static ma_decoding_backend_vtable g_ma_decoding_backend_vtable_libvorbis =
+{
+    ma_decoding_backend_init__libvorbis,
+    ma_decoding_backend_init_file__libvorbis,
+    NULL, /* onInitFileW() */
+    NULL, /* onInitMemory() */
+    ma_decoding_backend_uninit__libvorbis,
+    ma_decoding_backend_get_channel_map__libvorbis
+};
+
+
+
+static ma_result ma_decoding_backend_init__libopus(void* pUserData, ma_read_proc onRead, ma_seek_proc onSeek, ma_tell_proc onTell, void* pReadSeekTellUserData, const ma_decoding_backend_config* pConfig, const ma_allocation_callbacks* pAllocationCallbacks, ma_data_source** ppBackend)
+{
+    ma_result result;
+    ma_libopus* pOpus;
+
+    (void)pUserData;
+
+    pOpus = (ma_libopus*)ma_malloc(sizeof(*pOpus), pAllocationCallbacks);
+    if (pOpus == NULL) {
+        return MA_OUT_OF_MEMORY;
+    }
+
+    result = ma_libopus_init(onRead, onSeek, onTell, pReadSeekTellUserData, pConfig, pAllocationCallbacks, pOpus);
+    if (result != MA_SUCCESS) {
+        return result;
+    }
+
+    *ppBackend = pOpus;
+
+    return MA_SUCCESS;
+}
+
+static ma_result ma_decoding_backend_init_file__libopus(void* pUserData, const char* pFilePath, const ma_decoding_backend_config* pConfig, const ma_allocation_callbacks* pAllocationCallbacks, ma_data_source** ppBackend)
+{
+    ma_result result;
+    ma_libopus* pOpus;
+
+    (void)pUserData;
+
+    pOpus = (ma_libopus*)ma_malloc(sizeof(*pOpus), pAllocationCallbacks);
+    if (pOpus == NULL) {
+        return MA_OUT_OF_MEMORY;
+    }
+
+    result = ma_libopus_init_file(pFilePath, pConfig, pAllocationCallbacks, pOpus);
+    if (result != MA_SUCCESS) {
+        return result;
+    }
+
+    *ppBackend = pOpus;
+
+    return MA_SUCCESS;
+}
+
+static void ma_decoding_backend_uninit__libopus(void* pUserData, ma_data_source* pBackend, const ma_allocation_callbacks* pAllocationCallbacks)
+{
+    ma_libopus* pOpus = (ma_libopus*)pBackend;
+
+    (void)pUserData;
+
+    ma_libopus_uninit(pOpus, pAllocationCallbacks);
+    ma_free(pOpus, pAllocationCallbacks);
+}
+
+static ma_result ma_decoding_backend_get_channel_map__libopus(void* pUserData, ma_data_source* pBackend, ma_channel* pChannelMap, size_t channelMapCap)
+{
+    ma_libopus* pOpus = (ma_libopus*)pBackend;
+
+    (void)pUserData;
+
+    return ma_libopus_get_data_format(pOpus, NULL, NULL, NULL, pChannelMap, channelMapCap);
+}
+
+static ma_decoding_backend_vtable g_ma_decoding_backend_vtable_libopus =
+{
+    ma_decoding_backend_init__libopus,
+    ma_decoding_backend_init_file__libopus,
+    NULL, /* onInitFileW() */
+    NULL, /* onInitMemory() */
+    ma_decoding_backend_uninit__libopus,
+    ma_decoding_backend_get_channel_map__libopus
+};
+
+
+
+
+void data_callback(ma_device* pDevice, void* pOutput, const void* pInput, ma_uint32 frameCount)
+{
+    ma_data_source* pDataSource = (ma_data_source*)pDevice->pUserData;
+    if (pDataSource == NULL) {
+        return;
+    }
+
+    ma_data_source_read_pcm_frames(pDataSource, pOutput, frameCount, NULL, MA_TRUE);
+
+    (void)pInput;
+}
+
+int main(int argc, char** argv)
+{
+    ma_result result;
+    ma_resource_manager_config resourceManagerConfig;
+    ma_resource_manager resourceManager;
+    ma_engine_config engineConfig;
+    ma_engine engine;
+
+    /*
+    Add your custom backend vtables here. The order in the array defines the order of priority. The
+    vtables will be passed in via the decoder config.
+    */
+    ma_decoding_backend_vtable* pCustomBackendVTables[] =
+    {
+        &g_ma_decoding_backend_vtable_libvorbis,
+        &g_ma_decoding_backend_vtable_libopus
+    };
+
+
+    if (argc < 2) {
+        printf("No input file.\n");
+        return -1;
+    }
+
+
+    /* Using custom decoding backends requires a resource manager. */
+    resourceManagerConfig = ma_resource_manager_config_init();
+    resourceManagerConfig.ppCustomDecodingBackendVTables   = pCustomBackendVTables;
+    resourceManagerConfig.customDecodingBackendVTableCount = sizeof(pCustomBackendVTables) / sizeof(pCustomBackendVTables[0]);
+    resourceManagerConfig.pCustomDecodingBackendUserData   = NULL;  /* <-- This will be passed in to the pUserData parameter of each function in the decoding backend vtables. */
+
+    result = ma_resource_manager_init(&resourceManagerConfig, &resourceManager);
+    if (result != MA_SUCCESS) {
+        printf("Failed to initialize resource manager.");
+        return -1;
+    }
+
+
+    /* Once we have a resource manager we can create the engine. */
+    engineConfig = ma_engine_config_init();
+    engineConfig.pResourceManager = &resourceManager;
+
+    result = ma_engine_init(&engineConfig, &engine);
+    if (result != MA_SUCCESS) {
+        printf("Failed to initialize engine.");
+        return -1;
+    }
+
+
+    /* Now we can start our sound. */
+    result = ma_engine_play_sound(&engine, argv[1], NULL);
+    if (result != MA_SUCCESS) {
+        printf("Failed to play sound.");
+        return -1;
+    }
+
+
+    printf("Press Enter to quit...");
+    getchar();
+
+    return 0;
+}
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