Function WASAPI_PrepDevice

deps/SDL2/src/audio/wasapi/SDL_wasapi.c:494–659

This is called once a device is activated, possibly asynchronously. */

/* This is called once a device is activated, possibly asynchronously. */
int
WASAPI_PrepDevice(_THIS, const SDL_bool updatestream)
{
    /* !!! FIXME: we could request an exclusive mode stream, which is lower latency;
       !!!  it will write into the kernel's audio buffer directly instead of
       !!!  shared memory that a user-mode mixer then writes to the kernel with
       !!!  everything else. Doing this means any other sound using this device will
       !!!  stop playing, including the user's MP3 player and system notification
       !!!  sounds. You'd probably need to release the device when the app isn't in
       !!!  the foreground, to be a good citizen of the system. It's doable, but it's
       !!!  more work and causes some annoyances, and I don't know what the latency
       !!!  wins actually look like. Maybe add a hint to force exclusive mode at
       !!!  some point. To be sure, defaulting to shared mode is the right thing to
       !!!  do in any case. */
    const SDL_AudioSpec oldspec = this->spec;
    const AUDCLNT_SHAREMODE sharemode = AUDCLNT_SHAREMODE_SHARED;
    UINT32 bufsize = 0;  /* this is in sample frames, not samples, not bytes. */
    REFERENCE_TIME duration = 0;
    IAudioClient *client = this->hidden->client;
    IAudioRenderClient *render = NULL;
    IAudioCaptureClient *capture = NULL;
    WAVEFORMATEX *waveformat = NULL;
    SDL_AudioFormat test_format = SDL_FirstAudioFormat(this->spec.format);
    SDL_AudioFormat wasapi_format = 0;
    SDL_bool valid_format = SDL_FALSE;
    HRESULT ret = S_OK;
    DWORD streamflags = 0;

    SDL_assert(client != NULL);

#ifdef __WINRT__  /* CreateEventEx() arrived in Vista, so we need an #ifdef for XP. */
    this->hidden->event = CreateEventEx(NULL, NULL, 0, EVENT_ALL_ACCESS);
#else
    this->hidden->event = CreateEventW(NULL, 0, 0, NULL);
#endif

    if (this->hidden->event == NULL) {
        return WIN_SetError("WASAPI can't create an event handle");
    }

    ret = IAudioClient_GetMixFormat(client, &waveformat);
    if (FAILED(ret)) {
        return WIN_SetErrorFromHRESULT("WASAPI can't determine mix format", ret);
    }

    SDL_assert(waveformat != NULL);
    this->hidden->waveformat = waveformat;

    this->spec.channels = (Uint8) waveformat->nChannels;

    /* Make sure we have a valid format that we can convert to whatever WASAPI wants. */
    if ((waveformat->wFormatTag == WAVE_FORMAT_IEEE_FLOAT) && (waveformat->wBitsPerSample == 32)) {
        wasapi_format = AUDIO_F32SYS;
    } else if ((waveformat->wFormatTag == WAVE_FORMAT_PCM) && (waveformat->wBitsPerSample == 16)) {
        wasapi_format = AUDIO_S16SYS;
    } else if ((waveformat->wFormatTag == WAVE_FORMAT_PCM) && (waveformat->wBitsPerSample == 32)) {
        wasapi_format = AUDIO_S32SYS;
    } else if (waveformat->wFormatTag == WAVE_FORMAT_EXTENSIBLE) {