[Spice-devel] [PATCH spice-gtk 1/2] gstreamer: use custom playbin sink

[Snir Sheriber]

Use custom playbin sink instead of just appsink.
In order to allow playbin to choose decoders that requires
more complex pipelines (e.g. pipeline that requires color
space conversion & uses gl memory).
The new sink composed as such:
... ! autovideoconvert ! gldownload ! appsink
---
 src/channel-display-gst.c | 32 ++++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/src/channel-display-gst.c b/src/channel-display-gst.c
index f978602..af87fb5 100644
--- a/src/channel-display-gst.c
+++ b/src/channel-display-gst.c
@@ -38,6 +38,7 @@ typedef struct SpiceGstDecoder {
 
     GstAppSrc *appsrc;
     GstAppSink *appsink;
+    GstElement *sinkbin;
     GstElement *pipeline;
     GstClock *clock;
 
@@ -265,7 +266,7 @@ static void free_pipeline(SpiceGstDecoder *decoder)
 
     gst_element_set_state(decoder->pipeline, GST_STATE_NULL);
     gst_object_unref(decoder->appsrc);
-    gst_object_unref(decoder->appsink);
+    gst_object_unref(decoder->sinkbin);
     gst_object_unref(decoder->pipeline);
     gst_object_unref(decoder->clock);
     decoder->pipeline = NULL;
@@ -346,7 +347,8 @@ static gboolean create_pipeline(SpiceGstDecoder *decoder)
     GstAppSinkCallbacks appsink_cbs = { NULL };
     GstBus *bus;
 #if GST_CHECK_VERSION(1,9,0)
-    GstElement *playbin, *sink;
+    GstElement *playbin, *sinkbin, *convert, *download, *appsink;
+    GstPad *pad, *ghost_pad;
     SpiceGstPlayFlags flags;
     GstCaps *caps;
 
@@ -356,26 +358,39 @@ static gboolean create_pipeline(SpiceGstDecoder *decoder)
         return FALSE;
     }
 
-    sink = gst_element_factory_make("appsink", "sink");
-    if (sink == NULL) {
-        spice_warning("error upon creation of 'appsink' element");
+    convert = gst_element_factory_make("autovideoconvert", "autovideoconvert");
+    download = gst_element_factory_make("gldownload", "gldownload");
+    appsink = gst_element_factory_make("appsink", "appsink");
+    if ( !appsink || !convert || !download ) {
+        spice_warning("error upon creation of one of the bin elements");
         gst_object_unref(playbin);
         return FALSE;
     }
 
     caps = gst_caps_from_string("video/x-raw,format=BGRx");
-    g_object_set(sink,
+    g_object_set(appsink,
                  "caps", caps,
                  "sync", FALSE,
                  "drop", FALSE,
                  NULL);
     gst_caps_unref(caps);
 
+    /* Create advanced playbin sink by binning the appsink, gldownload and
+     * autovideoconvert elements together */
+    sinkbin = gst_bin_new("sink_bin");
+    gst_bin_add_many (GST_BIN (sinkbin), convert, download, appsink, NULL);
+    gst_element_link_many(convert, download, appsink, NULL);
+    pad = gst_element_get_static_pad (convert, "sink");
+    ghost_pad = gst_ghost_pad_new ("sink", pad);
+    gst_pad_set_active (ghost_pad, TRUE);
+    gst_element_add_pad (sinkbin, ghost_pad);
+    gst_object_unref (pad);
+
     g_signal_connect(playbin, "source-setup", G_CALLBACK(app_source_setup), decoder);
 
     g_object_set(playbin,
                  "uri", "appsrc://",
-                 "video-sink", gst_object_ref(sink),
+                 "video-sink", gst_object_ref(sinkbin),
                  NULL);
 
     /* Disable audio in playbin */
@@ -384,7 +399,8 @@ static gboolean create_pipeline(SpiceGstDecoder *decoder)
     g_object_set(playbin, "flags", flags, NULL);
 
     g_warn_if_fail(decoder->appsrc == NULL);
-    decoder->appsink = GST_APP_SINK(sink);
+    decoder->appsink = GST_APP_SINK(appsink);
+    decoder->sinkbin = sinkbin;
     decoder->pipeline = playbin;
 #else
     gchar *desc;
-- 
2.9.5