Ensure pre-roll frames are displayed when gstreamer backend is paused.

Perform a seek before transitioning from the stopped state to paused or
playing to force the pipeline to resupply the video sink with any
pre-roll buffer it may have previously ignored during loading.  And
don't assume showPrerollFrames to be true if the current state is not
stopped as the policy handling may have prevented an effectual state
change.

Change-Id: I288a70bc4da32f3534eab4b14702ca8f8fdb4222
Reviewed-by: Yoann Lopes <yoann.lopes@digia.com>

1 files changed, 4 insertions, 82 deletions

diff --git a/src/gsttools/qvideosurfacegstsink.cpp b/src/gsttools/qvideosurfacegstsink.cpp
index 36f8c049b..f3e2d884c 100644
--- a/src/gsttools/qvideosurfacegstsink.cpp
+++ b/src/gsttools/qvideosurfacegstsink.cpp
@@ -56,7 +56,6 @@ QVideoSurfaceGstDelegate::QVideoSurfaceGstDelegate(
     : m_surface(surface)
     , m_pool(0)
     , m_renderReturn(GST_FLOW_ERROR)
-    , m_lastPrerolledBuffer(0)
     , m_bytesPerLine(0)
     , m_startCanceled(false)
 {
@@ -74,7 +73,6 @@ QVideoSurfaceGstDelegate::QVideoSurfaceGstDelegate(
 
 QVideoSurfaceGstDelegate::~QVideoSurfaceGstDelegate()
 {
-    setLastPrerolledBuffer(0);
 }
 
 QList<QVideoFrame::PixelFormat> QVideoSurfaceGstDelegate::supportedPixelFormats(QAbstractVideoBuffer::HandleType handleType) const
@@ -209,23 +207,6 @@ GstFlowReturn QVideoSurfaceGstDelegate::render(GstBuffer *buffer)
     return m_renderReturn;
 }
 
-void QVideoSurfaceGstDelegate::setLastPrerolledBuffer(GstBuffer *prerolledBuffer)
-{
-    // discard previously stored buffer
-    if (m_lastPrerolledBuffer) {
-        gst_buffer_unref(m_lastPrerolledBuffer);
-        m_lastPrerolledBuffer = 0;
-    }
-
-    if (!prerolledBuffer)
-        return;
-
-    // store a reference to the buffer
-    Q_ASSERT(!m_lastPrerolledBuffer);
-    m_lastPrerolledBuffer = prerolledBuffer;
-    gst_buffer_ref(m_lastPrerolledBuffer);
-}
-
 void QVideoSurfaceGstDelegate::queuedStart()
 {
     if (!m_startCanceled) {
@@ -397,8 +378,6 @@ QVideoSurfaceGstSink *QVideoSurfaceGstSink::createSink(QAbstractVideoSurface *su
 
     sink->delegate = new QVideoSurfaceGstDelegate(surface);
 
-    g_signal_connect(G_OBJECT(sink), "notify::show-preroll-frame", G_CALLBACK(handleShowPrerollChange), sink);
-
     return sink;
 }
 
@@ -434,16 +413,15 @@ void QVideoSurfaceGstSink::class_init(gpointer g_class, gpointer class_data)
 
     sink_parent_class = reinterpret_cast<GstVideoSinkClass *>(g_type_class_peek_parent(g_class));
 
+    GstVideoSinkClass *video_sink_class = reinterpret_cast<GstVideoSinkClass *>(g_class);
+    video_sink_class->show_frame = QVideoSurfaceGstSink::show_frame;
+
     GstBaseSinkClass *base_sink_class = reinterpret_cast<GstBaseSinkClass *>(g_class);
     base_sink_class->get_caps = QVideoSurfaceGstSink::get_caps;
     base_sink_class->set_caps = QVideoSurfaceGstSink::set_caps;
     base_sink_class->buffer_alloc = QVideoSurfaceGstSink::buffer_alloc;
     base_sink_class->start = QVideoSurfaceGstSink::start;
     base_sink_class->stop = QVideoSurfaceGstSink::stop;
-    // base_sink_class->unlock = QVideoSurfaceGstSink::unlock; // Not implemented.
-    base_sink_class->event = QVideoSurfaceGstSink::event;
-    base_sink_class->preroll = QVideoSurfaceGstSink::preroll;
-    base_sink_class->render = QVideoSurfaceGstSink::render;
 
     GstElementClass *element_class = reinterpret_cast<GstElementClass *>(g_class);
     element_class->change_state = QVideoSurfaceGstSink::change_state;
@@ -709,27 +687,6 @@ void QVideoSurfaceGstSink::setFrameTimeStamps(QVideoFrame *frame, GstBuffer *buf
     }
 }
 
-void QVideoSurfaceGstSink::handleShowPrerollChange(GObject *o, GParamSpec *p, gpointer d)
-{
-    Q_UNUSED(o);
-    Q_UNUSED(p);
-    QVideoSurfaceGstSink *sink = reinterpret_cast<QVideoSurfaceGstSink *>(d);
-
-    gboolean value = true; // "show-preroll-frame" property is true by default
-    g_object_get(G_OBJECT(sink), "show-preroll-frame", &value, NULL);
-
-    GstBuffer *buffer = sink->delegate->lastPrerolledBuffer();
-    // Render the stored prerolled buffer if requested.
-    // e.g. player is in stopped mode, then seek operation is requested,
-    // surface now stores a prerolled frame, but doesn't display it until
-    // "show-preroll-frame" property is set to "true"
-    // when switching to pause or playing state.
-    if (value && buffer) {
-        sink->delegate->render(buffer);
-        sink->delegate->setLastPrerolledBuffer(0);
-    }
-}
-
 GstFlowReturn QVideoSurfaceGstSink::buffer_alloc(
         GstBaseSink *base, guint64 offset, guint size, GstCaps *caps, GstBuffer **buffer)
 {
@@ -842,44 +799,9 @@ gboolean QVideoSurfaceGstSink::stop(GstBaseSink *base)
     return TRUE;
 }
 
-gboolean QVideoSurfaceGstSink::unlock(GstBaseSink *base)
-{
-    Q_UNUSED(base);
-
-    return TRUE;
-}
-
-gboolean QVideoSurfaceGstSink::event(GstBaseSink *base, GstEvent *event)
-{
-    // discard prerolled frame
-    if (event->type == GST_EVENT_FLUSH_START) {
-        VO_SINK(base);
-        sink->delegate->setLastPrerolledBuffer(0);
-    }
-
-    return TRUE;
-}
-
-GstFlowReturn QVideoSurfaceGstSink::preroll(GstBaseSink *base, GstBuffer *buffer)
-{
-    VO_SINK(base);
-
-    gboolean value = true; // "show-preroll-frame" property is true by default
-    g_object_get(G_OBJECT(base), "show-preroll-frame", &value, NULL);
-    if (value) {
-        sink->delegate->setLastPrerolledBuffer(0); // discard prerolled buffer
-        return sink->delegate->render(buffer); // display frame
-    }
-
-    // otherwise keep a reference to the buffer to display it later
-    sink->delegate->setLastPrerolledBuffer(buffer);
-    return GST_FLOW_OK;
-}
-
-GstFlowReturn QVideoSurfaceGstSink::render(GstBaseSink *base, GstBuffer *buffer)
+GstFlowReturn QVideoSurfaceGstSink::show_frame(GstVideoSink *base, GstBuffer *buffer)
 {
     VO_SINK(base);
-    sink->delegate->setLastPrerolledBuffer(0); // discard prerolled buffer
     return sink->delegate->render(buffer);
 }