wasapi: Add a property for trying the AudioClient3 API

The AudioClient3 API is only available on Windows 10, and we will
automatically detect when it is available and use it.

However, using it for capturing audio with low latency and without
glitches seems to require setting the realtime priority of the entire
pipeline to "critical", which we cannot do from inside the element.

Hence, we can only enable that by default for wasapisink since
apps should be able to safely set the low-latency property to TRUE if
they need low-latency capture or playback.

4 files changed, 64 insertions, 8 deletions

diff --git a/sys/wasapi/gstwasapisink.c b/sys/wasapi/gstwasapisink.c
index 7ef0516f8..e6a0e826a 100644
--- a/sys/wasapi/gstwasapisink.c
+++ b/sys/wasapi/gstwasapisink.c
@@ -54,6 +54,7 @@ static GstStaticPadTemplate sink_template = GST_STATIC_PAD_TEMPLATE ("sink",
 #define DEFAULT_MUTE          FALSE
 #define DEFAULT_EXCLUSIVE     FALSE
 #define DEFAULT_LOW_LATENCY   FALSE
+#define DEFAULT_AUDIOCLIENT3  TRUE
 
 enum
 {
@@ -62,7 +63,8 @@ enum
   PROP_MUTE,
   PROP_DEVICE,
   PROP_EXCLUSIVE,
-  PROP_LOW_LATENCY
+  PROP_LOW_LATENCY,
+  PROP_AUDIOCLIENT3
 };
 
 static void gst_wasapi_sink_dispose (GObject * object);
@@ -132,6 +134,12 @@ gst_wasapi_sink_class_init (GstWasapiSinkClass * klass)
           "Optimize all settings for lowest latency",
           DEFAULT_LOW_LATENCY, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
 
+  g_object_class_install_property (gobject_class,
+      PROP_AUDIOCLIENT3,
+      g_param_spec_boolean ("use-audioclient3", "Use the AudioClient3 API",
+          "Use the Windows 10 AudioClient3 API when available",
+          DEFAULT_AUDIOCLIENT3, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
   gst_element_class_add_static_pad_template (gstelement_class, &sink_template);
   gst_element_class_set_static_metadata (gstelement_class, "WasapiSrc",
       "Sink/Audio",
@@ -155,6 +163,11 @@ gst_wasapi_sink_class_init (GstWasapiSinkClass * klass)
 static void
 gst_wasapi_sink_init (GstWasapiSink * self)
 {
+  self->role = DEFAULT_ROLE;
+  self->mute = DEFAULT_MUTE;
+  self->sharemode = AUDCLNT_SHAREMODE_SHARED;
+  self->low_latency = DEFAULT_LOW_LATENCY;
+  self->try_audioclient3 = DEFAULT_AUDIOCLIENT3;
   self->event_handle = CreateEvent (NULL, FALSE, FALSE, NULL);
 
   CoInitialize (NULL);
@@ -232,6 +245,9 @@ gst_wasapi_sink_set_property (GObject * object, guint prop_id,
     case PROP_LOW_LATENCY:
       self->low_latency = g_value_get_boolean (value);
       break;
+    case PROP_AUDIOCLIENT3:
+      self->try_audioclient3 = g_value_get_boolean (value);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -262,12 +278,24 @@ gst_wasapi_sink_get_property (GObject * object, guint prop_id,
     case PROP_LOW_LATENCY:
       g_value_set_boolean (value, self->low_latency);
       break;
+    case PROP_AUDIOCLIENT3:
+      g_value_set_boolean (value, self->try_audioclient3);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
   }
 }
 
+static gboolean
+gst_wasapi_sink_can_audioclient3 (GstWasapiSink * self)
+{
+  if (self->sharemode == AUDCLNT_SHAREMODE_SHARED &&
+      self->try_audioclient3 && gst_wasapi_util_have_audioclient3 ())
+    return TRUE;
+  return FALSE;
+}
+
 static GstCaps *
 gst_wasapi_sink_get_caps (GstBaseSink * bsink, GstCaps * filter)
 {
@@ -416,8 +444,7 @@ gst_wasapi_sink_prepare (GstAudioSink * asink, GstAudioRingBufferSpec * spec)
   guint bpf, rate, devicep_frames;
   HRESULT hr;
 
-  if (self->sharemode == AUDCLNT_SHAREMODE_SHARED &&
-      gst_wasapi_util_have_audioclient3 ()) {
+  if (gst_wasapi_sink_can_audioclient3 (self)) {
     if (!gst_wasapi_util_initialize_audioclient3 (GST_ELEMENT (self), spec,
             (IAudioClient3 *) self->client, self->mix_format, self->low_latency,
             &devicep_frames))
@@ -521,7 +548,7 @@ gst_wasapi_sink_unprepare (GstAudioSink * asink)
   GstWasapiSink *self = GST_WASAPI_SINK (asink);
 
   if (self->sharemode == AUDCLNT_SHAREMODE_EXCLUSIVE &&
-      !gst_wasapi_util_have_audioclient3 ())
+      !gst_wasapi_sink_can_audioclient3 (self))
     CoUninitialize ();
 
   if (self->thread_priority_handle != NULL) {
diff --git a/sys/wasapi/gstwasapisink.h b/sys/wasapi/gstwasapisink.h
index e445ce290..c17866991 100644
--- a/sys/wasapi/gstwasapisink.h
+++ b/sys/wasapi/gstwasapisink.h
@@ -62,6 +62,7 @@ struct _GstWasapiSink
   gint sharemode;
   gboolean mute;
   gboolean low_latency;
+  gboolean try_audioclient3;
   wchar_t *device_strid;
 };
 
diff --git a/sys/wasapi/gstwasapisrc.c b/sys/wasapi/gstwasapisrc.c
index 93b166e4d..f1fd6415d 100644
--- a/sys/wasapi/gstwasapisrc.c
+++ b/sys/wasapi/gstwasapisrc.c
@@ -51,6 +51,7 @@ static GstStaticPadTemplate src_template = GST_STATIC_PAD_TEMPLATE ("src",
 #define DEFAULT_ROLE          GST_WASAPI_DEVICE_ROLE_CONSOLE
 #define DEFAULT_EXCLUSIVE     FALSE
 #define DEFAULT_LOW_LATENCY   FALSE
+#define DEFAULT_AUDIOCLIENT3  FALSE
 
 enum
 {
@@ -58,7 +59,8 @@ enum
   PROP_ROLE,
   PROP_DEVICE,
   PROP_EXCLUSIVE,
-  PROP_LOW_LATENCY
+  PROP_LOW_LATENCY,
+  PROP_AUDIOCLIENT3
 };
 
 static void gst_wasapi_src_dispose (GObject * object);
@@ -124,6 +126,12 @@ gst_wasapi_src_class_init (GstWasapiSrcClass * klass)
           "Optimize all settings for lowest latency",
           DEFAULT_LOW_LATENCY, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
 
+  g_object_class_install_property (gobject_class,
+      PROP_AUDIOCLIENT3,
+      g_param_spec_boolean ("use-audioclient3", "Use the AudioClient3 API",
+          "Whether to use the Windows 10 AudioClient3 API when available",
+          DEFAULT_AUDIOCLIENT3, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
   gst_element_class_add_static_pad_template (gstelement_class, &src_template);
   gst_element_class_set_static_metadata (gstelement_class, "WasapiSrc",
       "Source/Audio",
@@ -155,6 +163,10 @@ gst_wasapi_src_init (GstWasapiSrc * self)
       gst_wasapi_src_get_time, gst_object_ref (self),
       (GDestroyNotify) gst_object_unref);
 
+  self->role = DEFAULT_ROLE;
+  self->sharemode = AUDCLNT_SHAREMODE_SHARED;
+  self->low_latency = DEFAULT_LOW_LATENCY;
+  self->try_audioclient3 = DEFAULT_AUDIOCLIENT3;
   self->event_handle = CreateEvent (NULL, FALSE, FALSE, NULL);
 
   CoInitialize (NULL);
@@ -229,6 +241,9 @@ gst_wasapi_src_set_property (GObject * object, guint prop_id,
     case PROP_LOW_LATENCY:
       self->low_latency = g_value_get_boolean (value);
       break;
+    case PROP_AUDIOCLIENT3:
+      self->try_audioclient3 = g_value_get_boolean (value);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -256,12 +271,24 @@ gst_wasapi_src_get_property (GObject * object, guint prop_id,
     case PROP_LOW_LATENCY:
       g_value_set_boolean (value, self->low_latency);
       break;
+    case PROP_AUDIOCLIENT3:
+      g_value_set_boolean (value, self->try_audioclient3);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
   }
 }
 
+static gboolean
+gst_wasapi_src_can_audioclient3 (GstWasapiSrc * self)
+{
+  if (self->sharemode == AUDCLNT_SHAREMODE_SHARED &&
+      self->try_audioclient3 && gst_wasapi_util_have_audioclient3 ())
+    return TRUE;
+  return FALSE;
+}
+
 static GstCaps *
 gst_wasapi_src_get_caps (GstBaseSrc * bsrc, GstCaps * filter)
 {
@@ -384,8 +411,7 @@ gst_wasapi_src_prepare (GstAudioSrc * asrc, GstAudioRingBufferSpec * spec)
   guint bpf, rate, devicep_frames, buffer_frames;
   HRESULT hr;
 
-  if (self->sharemode == AUDCLNT_SHAREMODE_SHARED &&
-      gst_wasapi_util_have_audioclient3 ()) {
+  if (gst_wasapi_src_can_audioclient3 (self)) {
     if (!gst_wasapi_util_initialize_audioclient3 (GST_ELEMENT (self), spec,
             (IAudioClient3 *) self->client, self->mix_format, self->low_latency,
             &devicep_frames))
@@ -466,7 +492,8 @@ gst_wasapi_src_unprepare (GstAudioSrc * asrc)
 {
   GstWasapiSrc *self = GST_WASAPI_SRC (asrc);
 
-  if (self->sharemode == AUDCLNT_SHAREMODE_EXCLUSIVE)
+  if (self->sharemode == AUDCLNT_SHAREMODE_EXCLUSIVE &&
+      !gst_wasapi_src_can_audioclient3 (self))
     CoUninitialize ();
 
   if (self->thread_priority_handle != NULL) {
diff --git a/sys/wasapi/gstwasapisrc.h b/sys/wasapi/gstwasapisrc.h
index ca3f64146..21e4647e8 100644
--- a/sys/wasapi/gstwasapisrc.h
+++ b/sys/wasapi/gstwasapisrc.h
@@ -63,6 +63,7 @@ struct _GstWasapiSrc
   gint role;
   gint sharemode;
   gboolean low_latency;
+  gboolean try_audioclient3;
   wchar_t *device_strid;
 };