Custom Decoder

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.

/*
For now these need to be declared before miniaudio.c due to some compatibility issues with the old
MINIAUDIO_IMPLEMENTATION system. This will change from version 0.12.
*/
#include "../extras/decoders/libvorbis/miniaudio_libvorbis.c"
#include "../extras/decoders/libopus/miniaudio_libopus.c"
#include "../miniaudio.c"

#include <stdio.h>


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);

    (void)pInput;
}

int main(int argc, char** argv)
{
    ma_result result;
    ma_decoder_config decoderConfig;
    ma_decoder decoder;
    ma_device_config deviceConfig;
    ma_device device;
    ma_format format;
    ma_uint32 channels;
    ma_uint32 sampleRate;

    /*
    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.
    */
    const ma_decoding_backend_vtable* pCustomBackendVTables[] =
    {
        ma_decoding_backend_libvorbis,
        ma_decoding_backend_libopus
    };


    if (argc < 2) {
        printf("No input file.\n");
        return -1;
    }

    
    /* Initialize the decoder. */
    decoderConfig = ma_decoder_config_init_default();
    decoderConfig.pCustomBackendUserData = NULL;  /* None of our decoders require user data, so this can be set to null. */
    decoderConfig.ppCustomBackendVTables = pCustomBackendVTables;
    decoderConfig.customBackendCount     = sizeof(pCustomBackendVTables) / sizeof(pCustomBackendVTables[0]);
    
    result = ma_decoder_init_file(argv[1], &decoderConfig, &decoder);
    if (result != MA_SUCCESS) {
        printf("Failed to initialize decoder.");
        return -1;
    }

    ma_data_source_set_looping(&decoder, MA_TRUE);


    /* Initialize the device. */
    result = ma_data_source_get_data_format(&decoder, &format, &channels, &sampleRate, NULL, 0);
    if (result != MA_SUCCESS) {
        printf("Failed to retrieve decoder data format.");
        ma_decoder_uninit(&decoder);
        return -1;
    }

    deviceConfig = ma_device_config_init(ma_device_type_playback);
    deviceConfig.playback.format   = format;
    deviceConfig.playback.channels = channels;
    deviceConfig.sampleRate        = sampleRate;
    deviceConfig.dataCallback      = data_callback;
    deviceConfig.pUserData         = &decoder;

    if (ma_device_init(NULL, &deviceConfig, &device) != MA_SUCCESS) {
        printf("Failed to open playback device.\n");
        ma_decoder_uninit(&decoder);
        return -1;
    }

    if (ma_device_start(&device) != MA_SUCCESS) {
        printf("Failed to start playback device.\n");
        ma_device_uninit(&device);
        ma_decoder_uninit(&decoder);
        return -1;
    }

    printf("Press Enter to quit...");
    getchar();

    ma_device_uninit(&device);
    ma_decoder_uninit(&decoder);

    return 0;
}