sys/dshowsrcwrapper/gstdshowvideosrc.*: Don't increase latency by queuing buffers in an async queue when the streamin...

Original commit message from CVS:
Patch by: Ole André Vadla Ravnås  <ole.andre.ravnas at tandberg com>
* sys/dshowsrcwrapper/gstdshowvideosrc.c: (PROP_DEVICE_NAME),
(gst_dshowvideosrc_class_init), (gst_dshowvideosrc_init),
(gst_dshowvideosrc_dispose), (gst_dshowvideosrc_stop),
(gst_dshowvideosrc_unlock), (gst_dshowvideosrc_unlock_stop),
(gst_dshowvideosrc_create), (gst_dshowvideosrc_push_buffer):
* sys/dshowsrcwrapper/gstdshowvideosrc.h:
Don't increase latency by queuing buffers in an async queue when
the streaming thread can't keep up or isn't scheduled often
enough for some other reason, but just drop the previous buffer
in that case. Also implement GstBaseSrc::unlock for faster
unlocking when shutting down. (#520892).

2 files changed, 71 insertions, 8 deletions

diff --git a/sys/dshowsrcwrapper/gstdshowvideosrc.c b/sys/dshowsrcwrapper/gstdshowvideosrc.c
index 79ed5963..a7692ad5 100644
--- a/sys/dshowsrcwrapper/gstdshowvideosrc.c
+++ b/sys/dshowsrcwrapper/gstdshowvideosrc.c
@@ -100,6 +100,8 @@ static GstStateChangeReturn gst_dshowvideosrc_change_state (GstElement *
 
 static gboolean gst_dshowvideosrc_start (GstBaseSrc * bsrc);
 static gboolean gst_dshowvideosrc_stop (GstBaseSrc * bsrc);
+static gboolean gst_dshowvideosrc_unlock (GstBaseSrc * bsrc);
+static gboolean gst_dshowvideosrc_unlock_stop (GstBaseSrc * bsrc);
 static gboolean gst_dshowvideosrc_set_caps (GstBaseSrc * bsrc, GstCaps * caps);
 static GstCaps *gst_dshowvideosrc_get_caps (GstBaseSrc * bsrc);
 static GstFlowReturn gst_dshowvideosrc_create (GstPushSrc * psrc,
@@ -170,6 +172,9 @@ gst_dshowvideosrc_class_init (GstDshowVideoSrcClass * klass)
   gstbasesrc_class->set_caps = GST_DEBUG_FUNCPTR (gst_dshowvideosrc_set_caps);
   gstbasesrc_class->start = GST_DEBUG_FUNCPTR (gst_dshowvideosrc_start);
   gstbasesrc_class->stop = GST_DEBUG_FUNCPTR (gst_dshowvideosrc_stop);
+  gstbasesrc_class->unlock = GST_DEBUG_FUNCPTR (gst_dshowvideosrc_unlock);
+  gstbasesrc_class->unlock_stop =
+      GST_DEBUG_FUNCPTR (gst_dshowvideosrc_unlock_stop);
 
   gstpushsrc_class->create = GST_DEBUG_FUNCPTR (gst_dshowvideosrc_create);
 
@@ -201,7 +206,10 @@ gst_dshowvideosrc_init (GstDshowVideoSrc * src, GstDshowVideoSrcClass * klass)
   src->pins_mediatypes = NULL;
   src->is_rgb = FALSE;
 
-  src->async_queue = g_async_queue_new ();
+  src->buffer_cond = g_cond_new ();
+  src->buffer_mutex = g_mutex_new ();
+  src->buffer = NULL;
+  src->stop_requested = FALSE;
 
   CoInitializeEx (NULL, COINIT_MULTITHREADED);
 
@@ -239,9 +247,19 @@ gst_dshowvideosrc_dispose (GObject * gobject)
     src->video_cap_filter = NULL;
   }
 
-  if (src->async_queue) {
-    g_async_queue_unref (src->async_queue);
-    src->async_queue = NULL;
+  if (src->buffer_mutex) {
+    g_mutex_free (src->buffer_mutex);
+    src->buffer_mutex = NULL;
+  }
+
+  if (src->buffer_cond) {
+    g_cond_free (src->buffer_cond);
+    src->buffer_cond = NULL;
+  }
+
+  if (src->buffer) {
+    gst_buffer_unref (src->buffer);
+    src->buffer = NULL;
   }
 
   CoUninitialize ();
@@ -511,6 +529,7 @@ gst_dshowvideosrc_get_caps (GstBaseSrc * basesrc)
               GstCaps *caps =
                   gst_dshowvideosrc_getcaps_from_streamcaps (src, capture_pin,
                   streamcaps);
+
               if (caps) {
                 gst_caps_append (src->caps, caps);
               }
@@ -791,12 +810,48 @@ gst_dshowvideosrc_stop (GstBaseSrc * bsrc)
   return TRUE;
 }
 
+static gboolean
+gst_dshowvideosrc_unlock (GstBaseSrc * bsrc)
+{
+  GstDshowVideoSrc *src = GST_DSHOWVIDEOSRC (bsrc);
+
+  g_mutex_lock (src->buffer_mutex);
+  src->stop_requested = TRUE;
+  g_cond_signal (src->buffer_cond);
+  g_mutex_unlock (src->buffer_mutex);
+
+  return TRUE;
+}
+
+static gboolean
+gst_dshowvideosrc_unlock_stop (GstBaseSrc * bsrc)
+{
+  GstDshowVideoSrc *src = GST_DSHOWVIDEOSRC (bsrc);
+
+  src->stop_requested = FALSE;
+
+  return TRUE;
+}
+
 static GstFlowReturn
 gst_dshowvideosrc_create (GstPushSrc * psrc, GstBuffer ** buf)
 {
   GstDshowVideoSrc *src = GST_DSHOWVIDEOSRC (psrc);
 
-  *buf = g_async_queue_pop (src->async_queue);
+  g_mutex_lock (src->buffer_mutex);
+  while (src->buffer == NULL && !src->stop_requested)
+    g_cond_wait (src->buffer_cond, src->buffer_mutex);
+  *buf = src->buffer;
+  src->buffer = NULL;
+  g_mutex_unlock (src->buffer_mutex);
+
+  if (src->stop_requested) {
+    if (*buf != NULL) {
+      gst_buffer_unref (*buf);
+      *buf = NULL;
+    }
+    return GST_FLOW_WRONG_STATE;
+  }
 
   GST_CAT_DEBUG (dshowvideosrc_debug,
       "dshowvideosrc_create => pts %" GST_TIME_FORMAT " duration %"
@@ -998,7 +1053,12 @@ gst_dshowvideosrc_push_buffer (byte * buffer, long size, byte * src_object,
   /* the negotiate() method already set caps on the source pad */
   gst_buffer_set_caps (buf, GST_PAD_CAPS (GST_BASE_SRC_PAD (src)));
 
-  g_async_queue_push (src->async_queue, buf);
+  g_mutex_lock (src->buffer_mutex);
+  if (src->buffer != NULL)
+    gst_buffer_unref (src->buffer);
+  src->buffer = buf;
+  g_cond_signal (src->buffer_cond);
+  g_mutex_unlock (src->buffer_mutex);
 
   return TRUE;
 }
diff --git a/sys/dshowsrcwrapper/gstdshowvideosrc.h b/sys/dshowsrcwrapper/gstdshowvideosrc.h
index 994326fd..8bc52fa9 100644
--- a/sys/dshowsrcwrapper/gstdshowvideosrc.h
+++ b/sys/dshowsrcwrapper/gstdshowvideosrc.h
@@ -66,8 +66,11 @@ struct _GstDshowVideoSrc
   IMediaFilter *media_filter;
   IFilterGraph *filter_graph;
 
-  /* async queue which will contain incoming buffers from directshow */
-  GAsyncQueue *async_queue;
+  /* the last buffer from DirectShow */
+  GCond * buffer_cond;
+  GMutex * buffer_mutex;
+  GstBuffer * buffer;
+  gboolean stop_requested;
 
   gboolean is_rgb;
   gint width;