Implement CUBEB_STREAM_PREF_EXCLUSIVE

Author: spycrab

include/cubeb/cubeb.h

@@ -217,11 +217,16 @@ typedef enum {
 
 /** Miscellaneous stream preferences. */
 typedef enum {
-  CUBEB_STREAM_PREF_NONE     = 0x00, /**< No stream preferences are requested. */
-  CUBEB_STREAM_PREF_LOOPBACK = 0x01 /**< Request a loopback stream. Should be
-                                         specified on the input params and an
-                                         output device to loopback from should
-                                         be passed in place of an input device. */
+    CUBEB_STREAM_PREF_NONE     = 0x00, /**< No stream preferences are requested. */
+    CUBEB_STREAM_PREF_LOOPBACK = 0x01, /**< Request a loopback stream. Should be
+                                       specified on the input params and an
+                                       output device to loopback from should
+                                       be passed in place of an input device. */
+    CUBEB_STREAM_PREF_EXCLUSIVE = 0x02 /**< (Windows / WASAPI only) Request that
+                                       this stream is run in exclusive mode
+                                       which results in lower latency but
+                                       doesn't allow other applications to
+                                       use the same device */
 } cubeb_stream_prefs;
 
 /** Stream format initialization parameters. */

src/cubeb.c

@@ -318,6 +318,11 @@ cubeb_stream_init(cubeb * context, cubeb_stream ** stream, char const * stream_n
     return r;
   }
 
+  if ((output_stream_params && output_stream_params->prefs) & CUBEB_STREAM_PREF_EXCLUSIVE || (input_stream_params && input_stream_params->prefs & CUBEB_STREAM_PREF_EXCLUSIVE)) {
+    if (strcmp(cubeb_get_backend_id(context), "wasapi") != 0)
+      return CUBEB_ERROR_NOT_SUPPORTED;
+  }
+
   r = context->ops->stream_init(context, stream, stream_name,
                                 input_device,
                                 input_stream_params,

src/cubeb_wasapi.cpp

@@ -617,9 +617,20 @@ refill(cubeb_stream * stm, void * input_buffer, long input_frames_count,
 
 int wasapi_stream_reset_default_device(cubeb_stream * stm);
 
+/* Helper for making get_input_buffer work in exclusive mode */
+HRESULT get_next_packet_size(cubeb_stream * stm, PUINT32 next)
+{
+    if (stm->input_stream_params.prefs & CUBEB_STREAM_PREF_EXCLUSIVE) {
+        *next = stm->input_buffer_frame_count;
+        return S_OK;
+    } else {
+        return stm->capture_client->GetNextPacketSize(next);
+    }
+}
+
 /* This helper grabs all the frames available from a capture client, put them in
  * linear_input_buffer. linear_input_buffer should be cleared before the
- * callback exits. This helper does not work with exclusive mode streams. */
+ * callback exits. */
 bool get_input_buffer(cubeb_stream * stm)
 {
   XASSERT(has_input(stm));
@@ -636,9 +647,9 @@ bool get_input_buffer(cubeb_stream * stm)
   // single packet each time. However, if we're pulling from the stream we may
   // need to grab multiple packets worth of frames that have accumulated (so
   // need a loop).
-  for (hr = stm->capture_client->GetNextPacketSize(&next);
+  for (hr = get_next_packet_size(stm, &next);
        next > 0;
-       hr = stm->capture_client->GetNextPacketSize(&next)) {
+       hr = get_next_packet_size(stm, &next)) {
     if (hr == AUDCLNT_E_DEVICE_INVALIDATED) {
       // Application can recover from this error. More info
       // https://msdn.microsoft.com/en-us/library/windows/desktop/dd316605(v=vs.85).aspx
@@ -705,6 +716,9 @@ bool get_input_buffer(cubeb_stream * stm)
       return false;
     }
     offset += packet_size;
+
+    if (stm->input_stream_params.prefs & CUBEB_STREAM_PREF_EXCLUSIVE)
+      break;
   }
 
   XASSERT(stm->linear_input_buffer->length() >= offset);
@@ -1395,8 +1409,11 @@ wasapi_get_min_latency(cubeb * ctx, cubeb_stream_params params, uint32_t * laten
     return CUBEB_ERROR;
   }
 
-  /* The second parameter is for exclusive mode, that we don't use. */
-  hr = client->GetDevicePeriod(&default_period, NULL);
+  if (params.prefs & CUBEB_STREAM_PREF_EXCLUSIVE)
+      hr = client->GetDevicePeriod(NULL, &default_period);
+  else
+      hr = client->GetDevicePeriod(&default_period, NULL);
+
   if (FAILED(hr)) {
     LOG("Could not get device period: %lx", hr);
     return CUBEB_ERROR;
@@ -1531,7 +1548,7 @@ handle_channel_layout(cubeb_stream * stm,  EDataFlow direction, com_heap_ptr<WAV
 
   /* Check if wasapi will accept our channel layout request. */
   WAVEFORMATEX * closest;
-  HRESULT hr = audio_client->IsFormatSupported(AUDCLNT_SHAREMODE_SHARED,
+  HRESULT hr = audio_client->IsFormatSupported(stream_params->prefs & CUBEB_STREAM_PREF_EXCLUSIVE ? AUDCLNT_SHAREMODE_EXCLUSIVE : AUDCLNT_SHAREMODE_SHARED,
                                                mix_format.get(),
                                                &closest);
   if (hr == S_FALSE) {
@@ -1665,6 +1682,13 @@ int setup_wasapi_stream_one_side(cubeb_stream * stm,
     // audio according to layout.
     LOG("Channel count is different from the layout standard!\n");
   }
+
+
+  if (stream_params->prefs & CUBEB_STREAM_PREF_EXCLUSIVE)
+      LOG("Setup requested=[f=%d r=%u c=%u] mix=[f=%d r=%u c=%u]",
+          stream_params->format, stream_params->rate, stream_params->channels,
+          mix_params->format, mix_params->rate, mix_params->channels);
+  else
   LOG("Setup requested=[f=%d r=%u c=%u l=%s] mix=[f=%d r=%u c=%u l=%s]",
       stream_params->format, stream_params->rate, stream_params->channels,
       CUBEB_CHANNEL_LAYOUT_MAPS[stream_params->layout].name,
@@ -1681,10 +1705,10 @@ int setup_wasapi_stream_one_side(cubeb_stream * stm,
     flags |= AUDCLNT_STREAMFLAGS_EVENTCALLBACK;
   }
 
-  hr = audio_client->Initialize(AUDCLNT_SHAREMODE_SHARED,
+  hr = audio_client->Initialize(stream_params->prefs & CUBEB_STREAM_PREF_EXCLUSIVE ? AUDCLNT_SHAREMODE_EXCLUSIVE : AUDCLNT_SHAREMODE_SHARED,
                                 flags,
                                 frames_to_hns(stm, stm->latency),
-                                0,
+                                stream_params->prefs & CUBEB_STREAM_PREF_EXCLUSIVE ? frames_to_hns(stm, stm->latency) : 0,
                                 mix_format.get(),
                                 NULL);
   if (FAILED(hr)) {