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ao_wasapi: replace laggy COM messaging with mp_dispatch_queue
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A COM message loop is apparently totally inappropriate for a low latency
thread. It leads to audio glitches because the thread doesn't wake up fast
enough when it should. It also causes mysterious correlations between the vo
and ao thread (i.e., toggling fullscreen delays audio feed events). Instead use
an mp_dispatch_queue to set/get volume/mute/session display name from the audio
thread. This has the added benefit of obviating the need to marshal the
associated interfaces from the audio thread.
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@kevmitch
kevmitch committed Feb 26, 2016
1 parent 3153988 commit 84a3c21
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Showing 3 changed files with 80 additions and 175 deletions.
146 changes: 78 additions & 68 deletions audio/out/ao_wasapi.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
#include "options/m_option.h"
#include "osdep/timer.h"
#include "osdep/io.h"
#include "misc/dispatch.h"
#include "ao_wasapi.h"

// naive av_rescale for unsigned
Expand Down Expand Up @@ -188,6 +189,21 @@ static void thread_reset(struct ao *ao)
return;
}

static void thread_wakeup(void *ptr)
{
struct ao *ao = ptr;
struct wasapi_state *state = ao->priv;
SetEvent(state->hWake);
}

static void set_thread_state(struct ao *ao,
enum wasapi_thread_state thread_state)
{
struct wasapi_state *state = ao->priv;
atomic_store(&state->thread_state, thread_state);
thread_wakeup(ao);
}

static DWORD __stdcall AudioThread(void *lpParameter)
{
struct ao *ao = lpParameter;
Expand All @@ -200,41 +216,31 @@ static DWORD __stdcall AudioThread(void *lpParameter)
goto exit_label;

MP_DBG(ao, "Entering dispatch loop\n");
while (true) { // watch events
HANDLE events[] = {state->hWake};
switch (MsgWaitForMultipleObjects(MP_ARRAY_SIZE(events), events,
FALSE, INFINITE,
QS_POSTMESSAGE | QS_SENDMESSAGE)) {
// AudioThread wakeup
case WAIT_OBJECT_0:
switch (atomic_load(&state->thread_state)) {
case WASAPI_THREAD_FEED:
// fill twice on under-full buffer (see comment in thread_feed)
if (thread_feed(ao) && thread_feed(ao))
MP_ERR(ao, "Unable to fill buffer fast enough\n");
break;
case WASAPI_THREAD_RESET:
thread_reset(ao);
break;
case WASAPI_THREAD_RESUME:
thread_reset(ao);
thread_resume(ao);
break;
case WASAPI_THREAD_SHUTDOWN:
thread_reset(ao);
goto exit_label;
default:
MP_ERR(ao, "Unhandled thread state\n");
goto exit_label;
}
while (true) {
if (WaitForSingleObject(state->hWake, INFINITE) != WAIT_OBJECT_0)
MP_ERR(ao, "Unexpected return value from WaitForSingleObject\n");

mp_dispatch_queue_process(state->dispatch, 0);

int thread_state = atomic_load(&state->thread_state);
switch (thread_state) {
case WASAPI_THREAD_FEED:
// fill twice on under-full buffer (see comment in thread_feed)
if (thread_feed(ao) && thread_feed(ao))
MP_ERR(ao, "Unable to fill buffer fast enough\n");
break;
// messages to dispatch (COM marshalling)
case (WAIT_OBJECT_0 + MP_ARRAY_SIZE(events)):
wasapi_dispatch(ao);
case WASAPI_THREAD_RESET:
thread_reset(ao);
break;
default:
MP_ERR(ao, "Unhandled thread event\n");
case WASAPI_THREAD_RESUME:
thread_reset(ao);
thread_resume(ao);
break;
case WASAPI_THREAD_SHUTDOWN:
thread_reset(ao);
goto exit_label;
default:
MP_ERR(ao, "Unhandled thread state: %d\n", thread_state);
}
}
exit_label:
Expand All @@ -245,19 +251,10 @@ static DWORD __stdcall AudioThread(void *lpParameter)
return 0;
}

static void set_thread_state(struct ao *ao,
enum wasapi_thread_state thread_state)
{
struct wasapi_state *state = ao->priv;
atomic_store(&state->thread_state, thread_state);
SetEvent(state->hWake);
}

static void uninit(struct ao *ao)
{
MP_DBG(ao, "Uninit wasapi\n");
struct wasapi_state *state = ao->priv;
wasapi_release_proxies(state);
if (state->hWake)
set_thread_state(ao, WASAPI_THREAD_SHUTDOWN);

Expand Down Expand Up @@ -305,6 +302,9 @@ static int init(struct ao *ao)
return -1;
}

state->dispatch = mp_dispatch_create(state);
mp_dispatch_set_wakeup_fn(state->dispatch, thread_wakeup, ao);

state->init_ret = E_FAIL;
state->hAudioThread = CreateThread(NULL, 0, &AudioThread, ao, 0, NULL);
if (!state->hAudioThread) {
Expand All @@ -322,19 +322,18 @@ static int init(struct ao *ao)
return -1;
}

wasapi_receive_proxies(state);
MP_DBG(ao, "Init wasapi done\n");
return 0;
}

static int control_exclusive(struct ao *ao, enum aocontrol cmd, void *arg)
static int thread_control_exclusive(struct ao *ao, enum aocontrol cmd, void *arg)
{
struct wasapi_state *state = ao->priv;

switch (cmd) {
case AOCONTROL_GET_VOLUME:
case AOCONTROL_SET_VOLUME:
if (!state->pEndpointVolumeProxy ||
if (!state->pEndpointVolume ||
!(state->vol_hw_support & ENDPOINT_HARDWARE_SUPPORT_VOLUME)) {
return CONTROL_FALSE;
}
Expand All @@ -343,8 +342,7 @@ static int control_exclusive(struct ao *ao, enum aocontrol cmd, void *arg)
switch (cmd) {
case AOCONTROL_GET_VOLUME:
IAudioEndpointVolume_GetMasterVolumeLevelScalar(
state->pEndpointVolumeProxy,
&volume);
state->pEndpointVolume, &volume);
*(ao_control_vol_t *)arg = (ao_control_vol_t){
.left = 100.0f * volume,
.right = 100.0f * volume,
Expand All @@ -353,28 +351,25 @@ static int control_exclusive(struct ao *ao, enum aocontrol cmd, void *arg)
case AOCONTROL_SET_VOLUME:
volume = ((ao_control_vol_t *)arg)->left / 100.f;
IAudioEndpointVolume_SetMasterVolumeLevelScalar(
state->pEndpointVolumeProxy,
volume, NULL);
state->pEndpointVolume, volume, NULL);
return CONTROL_OK;
}
case AOCONTROL_GET_MUTE:
case AOCONTROL_SET_MUTE:
if (!state->pEndpointVolumeProxy ||
if (!state->pEndpointVolume ||
!(state->vol_hw_support & ENDPOINT_HARDWARE_SUPPORT_MUTE)) {
return CONTROL_FALSE;
}

BOOL mute;
switch (cmd) {
case AOCONTROL_GET_MUTE:
IAudioEndpointVolume_GetMute(state->pEndpointVolumeProxy,
&mute);
IAudioEndpointVolume_GetMute(state->pEndpointVolume, &mute);
*(bool *)arg = mute;
return CONTROL_OK;
case AOCONTROL_SET_MUTE:
mute = *(bool *)arg;
IAudioEndpointVolume_SetMute(state->pEndpointVolumeProxy,
mute, NULL);
IAudioEndpointVolume_SetMute(state->pEndpointVolume, mute, NULL);
return CONTROL_OK;
}
case AOCONTROL_HAS_PER_APP_VOLUME:
Expand All @@ -384,35 +379,33 @@ static int control_exclusive(struct ao *ao, enum aocontrol cmd, void *arg)
}
}

static int control_shared(struct ao *ao, enum aocontrol cmd, void *arg)
static int thread_control_shared(struct ao *ao, enum aocontrol cmd, void *arg)
{
struct wasapi_state *state = ao->priv;
if (!state->pAudioVolumeProxy)
if (!state->pAudioVolume)
return CONTROL_UNKNOWN;

float volume;
BOOL mute;
switch(cmd) {
case AOCONTROL_GET_VOLUME:
ISimpleAudioVolume_GetMasterVolume(state->pAudioVolumeProxy,
&volume);
ISimpleAudioVolume_GetMasterVolume(state->pAudioVolume, &volume);
*(ao_control_vol_t *)arg = (ao_control_vol_t){
.left = 100.0f * volume,
.right = 100.0f * volume,
};
return CONTROL_OK;
case AOCONTROL_SET_VOLUME:
volume = ((ao_control_vol_t *)arg)->left / 100.f;
ISimpleAudioVolume_SetMasterVolume(state->pAudioVolumeProxy,
volume, NULL);
ISimpleAudioVolume_SetMasterVolume(state->pAudioVolume, volume, NULL);
return CONTROL_OK;
case AOCONTROL_GET_MUTE:
ISimpleAudioVolume_GetMute(state->pAudioVolumeProxy, &mute);
ISimpleAudioVolume_GetMute(state->pAudioVolume, &mute);
*(bool *)arg = mute;
return CONTROL_OK;
case AOCONTROL_SET_MUTE:
mute = *(bool *)arg;
ISimpleAudioVolume_SetMute(state->pAudioVolumeProxy, mute, NULL);
ISimpleAudioVolume_SetMute(state->pAudioVolume, mute, NULL);
return CONTROL_OK;
case AOCONTROL_HAS_PER_APP_VOLUME:
return CONTROL_TRUE;
Expand All @@ -421,14 +414,14 @@ static int control_shared(struct ao *ao, enum aocontrol cmd, void *arg)
}
}

static int control(struct ao *ao, enum aocontrol cmd, void *arg)
static int thread_control(struct ao *ao, enum aocontrol cmd, void *arg)
{
struct wasapi_state *state = ao->priv;

// common to exclusive and shared
switch (cmd) {
case AOCONTROL_UPDATE_STREAM_TITLE:
if (!state->pSessionControlProxy)
if (!state->pSessionControl)
return CONTROL_FALSE;

wchar_t *title = mp_from_utf8(NULL, (char*)arg);
Expand All @@ -437,20 +430,37 @@ static int control(struct ao *ao, enum aocontrol cmd, void *arg)
// it seems that *sometimes* the SetDisplayName does not take effect and
// it still shows the old title. Use this loop to insist until it works.
do {
IAudioSessionControl_SetDisplayName(state->pSessionControlProxy,
title, NULL);
IAudioSessionControl_SetDisplayName(state->pSessionControl, title, NULL);

SAFE_RELEASE(tmp, CoTaskMemFree(tmp));
IAudioSessionControl_GetDisplayName(state->pSessionControlProxy,
&tmp);
IAudioSessionControl_GetDisplayName(state->pSessionControl, &tmp);
} while (lstrcmpW(title, tmp));
SAFE_RELEASE(tmp, CoTaskMemFree(tmp));
talloc_free(title);
return CONTROL_OK;
}

return state->share_mode == AUDCLNT_SHAREMODE_EXCLUSIVE ?
control_exclusive(ao, cmd, arg) : control_shared(ao, cmd, arg);
thread_control_exclusive(ao, cmd, arg) :
thread_control_shared(ao, cmd, arg);
}

static void run_control(void *p)
{
void **pp = p;
struct ao *ao = pp[0];
enum aocontrol cmd = *(enum aocontrol *)pp[1];
void *arg = pp[2];
*(int *)pp[3] = thread_control(ao, cmd, arg);
}

static int control(struct ao *ao, enum aocontrol cmd, void *arg)
{
struct wasapi_state *state = ao->priv;
int ret;
void *p[] = {ao, &cmd, arg, &ret};
mp_dispatch_run(state->dispatch, run_control, p);
return ret;
}

static void audio_reset(struct ao *ao)
Expand Down
16 changes: 2 additions & 14 deletions audio/out/ao_wasapi.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,7 @@ typedef struct wasapi_state {
HANDLE hAudioThread; // the audio thread itself
HANDLE hWake; // thread wakeup event
atomic_int thread_state; // enum wasapi_thread_state (what to do on wakeup)
struct mp_dispatch_queue *dispatch; // for volume/mute/session display

// for setting the audio thread priority
HANDLE hTask;
Expand All @@ -83,25 +84,12 @@ typedef struct wasapi_state {
UINT64 clock_frequency; // scale for position returned by GetPosition
LARGE_INTEGER qpc_frequency; // frequency of Windows' high resolution timer

// WASAPI control (handles owned by audio thread but used by main thread)
// WASAPI control
IAudioSessionControl *pSessionControl; // setting the stream title
IAudioEndpointVolume *pEndpointVolume; // exclusive mode volume/mute
ISimpleAudioVolume *pAudioVolume; // shared mode volume/mute
DWORD vol_hw_support; // is hardware volume supported for exclusive-mode?

// Streams used to marshal the proxy objects. The thread owning the actual
// objects needs to marshal proxy objects into these streams, and the thread
// that wants the proxies unmarshals them from here.
IStream *sSessionControl;
IStream *sEndpointVolume;
IStream *sAudioVolume;

// WASAPI proxy handles, for Single-Threaded Apartment communication. One is
// needed for each audio thread object that's accessed from the main thread.
IAudioSessionControl *pSessionControlProxy;
IAudioEndpointVolume *pEndpointVolumeProxy;
ISimpleAudioVolume *pAudioVolumeProxy;

// ao options
int opt_exclusive;
int opt_list;
Expand Down
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