HRESULT wasapi_change_init(struct ao *ao)
{
MP_DBG(ao, "Setting up monitoring on playback device\n");
struct wasapi_state *state = (struct wasapi_state *)ao->priv;
struct change_notify *change = &state->change;
/* COM voodoo to emulate c++ class */
change->client.lpVtbl = &sIMMDeviceEnumeratorVtbl_vtbl;
/* so the callbacks can access the ao */
change->ao = ao;
/* get the device string to compare with the pwstrDeviceId argument in callbacks */
HRESULT hr = IMMDevice_GetId(state->pDevice, &change->monitored);
EXIT_ON_ERROR(hr);
/* register the change notification client */
hr = IMMDeviceEnumerator_RegisterEndpointNotificationCallback(
state->pEnumerator, (IMMNotificationClient *)change);
EXIT_ON_ERROR(hr);
MP_VERBOSE(state, "Monitoring changes in device: %S\n", state->change.monitored);
return hr;
exit_label:
MP_ERR(state, "Error setting up device change monitoring: %s\n",
wasapi_explain_err(hr));
wasapi_change_uninit(ao);
return hr;
}
static double get_device_delay(struct wasapi_state *state) {
UINT64 sample_count = atomic_load(&state->sample_count);
UINT64 position, qpc_position;
HRESULT hr;
switch (hr = IAudioClock_GetPosition(state->pAudioClock, &position, &qpc_position)) {
case S_OK: case S_FALSE:
break;
default:
MP_ERR(state, "IAudioClock::GetPosition returned %s\n", wasapi_explain_err(hr));
}
LARGE_INTEGER qpc_count;
QueryPerformanceCounter(&qpc_count);
double qpc_diff = (qpc_count.QuadPart * 1e7 / state->qpc_frequency.QuadPart) - qpc_position;
position += state->clock_frequency * (uint64_t)(qpc_diff / 1e7);
/* convert position to the same base as sample_count */
position = position * state->format.Format.nSamplesPerSec / state->clock_frequency;
double diff = sample_count - position;
double delay = diff / state->format.Format.nSamplesPerSec;
MP_TRACE(state, "device delay: %g samples (%g ms)\n", diff, delay * 1000);
return delay;
}