[vlc-devel] [PATCH 2/2] wasapi: add loopback mode

[Rémi Denis-Courmont]

---
 modules/access/wasapi.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/modules/access/wasapi.c b/modules/access/wasapi.c
index 387546c..3a0c67e 100644
--- a/modules/access/wasapi.c
+++ b/modules/access/wasapi.c
@@ -73,6 +73,7 @@ struct demux_sys_t
     IAudioClient *client;
     es_out_id_t *es;
 
+    bool loopback;
     size_t frame_size;
     mtime_t caching;
     mtime_t start_time;
@@ -82,12 +83,14 @@ struct demux_sys_t
     SYNCHRONIZATION_BARRIER ready;
 };
 
-static IAudioClient *GetClient(demux_t *demux)
+static IAudioClient *GetClient(demux_t *demux, bool loopback)
 {
     IMMDeviceEnumerator *e;
     IMMDevice *dev;
     void *pv;
     HRESULT hr;
+    EDataFlow flow = loopback ? eRender : eCapture;
+    ERole role = loopback ? eConsole : eCommunications;
 
     hr = CoCreateInstance(&CLSID_MMDeviceEnumerator, NULL, CLSCTX_ALL,
                           &IID_IMMDeviceEnumerator, &pv);
@@ -98,8 +101,7 @@ static IAudioClient *GetClient(demux_t *demux)
     }
     e = pv;
 
-    hr = IMMDeviceEnumerator_GetDefaultAudioEndpoint(e, eCapture,
-                                                     eCommunications, &dev);
+    hr = IMMDeviceEnumerator_GetDefaultAudioEndpoint(e, flow, role, &dev);
     IMMDeviceEnumerator_Release(e);
     if (FAILED(hr))
     {
@@ -214,7 +216,7 @@ static int vlc_FromWave(const WAVEFORMATEX *restrict wf,
     return 0;
 }
 
-static es_out_id_t *CreateES(demux_t *demux, IAudioClient *client,
+static es_out_id_t *CreateES(demux_t *demux, IAudioClient *client, bool loop,
                              mtime_t caching, size_t *restrict frame_size)
 {
     es_format_t fmt;
@@ -241,7 +243,10 @@ static es_out_id_t *CreateES(demux_t *demux, IAudioClient *client,
                                               * fmt.audio.i_rate;
     *frame_size = fmt.audio.i_bitspersample * fmt.audio.i_channels / 8;
 
-    DWORD flags = AUDCLNT_STREAMFLAGS_EVENTCALLBACK; /* TODO: loopback */
+    DWORD flags = AUDCLNT_STREAMFLAGS_EVENTCALLBACK;
+    if (loop)
+        flags |= AUDCLNT_STREAMFLAGS_LOOPBACK;
+
     /* Request at least thrice the PTS delay */
     REFERENCE_TIME bufsize = caching * INT64_C(10000) * 3;
 
@@ -368,6 +373,7 @@ static int Open(vlc_object_t *obj)
 
     sys->client = NULL;
     sys->es = NULL;
+    sys->loopback = var_InheritBool(obj, "wasapi-loopback");
     sys->caching = INT64_C(1000) * var_InheritInteger(obj, "live-caching");
     sys->start_time = mdate();
     for (unsigned i = 0; i < 2; i++)
@@ -385,13 +391,14 @@ static int Open(vlc_object_t *obj)
         goto error;
     }
 
-    sys->client = GetClient(demux);
+    sys->client = GetClient(demux, sys->loopback);
     if (sys->client == NULL) {
         CoUninitialize();
         goto error;
     }
 
-    sys->es = CreateES(demux, sys->client, sys->caching, &sys->frame_size);
+    sys->es = CreateES(demux, sys->client, sys->loopback, sys->caching,
+                       &sys->frame_size);
     if (sys->es == NULL)
         goto error;
 
@@ -455,6 +462,9 @@ static void Close (vlc_object_t *obj)
     free(sys);
 }
 
+#define LOOPBACK_TEXT N_("Loopback mode")
+#define LOOPBACK_LONGTEXT N_("Record an audio rendering endpoint.")
+
 vlc_module_begin()
     set_shortname(N_("WASAPI"))
     set_description(N_("Windows Audio Session API input"))
@@ -462,6 +472,8 @@ vlc_module_begin()
     set_category(CAT_INPUT)
     set_subcategory(SUBCAT_INPUT_ACCESS)
 
+    add_bool("wasapi-loopback", false, LOOPBACK_TEXT, LOOPBACK_LONGTEXT, true)
+
     add_shortcut("wasapi")
     set_callbacks(Open, Close)
 vlc_module_end()
-- 
2.1.4