v4l2videodec: Add dynamic resolution change support

This implements a "big hammer" reallocation method. We effectively
drain and stop both side of the decoder and restart. This though is
the most generic method. This change should enable on most drivers
adaptive streaming.

https://bugzilla.gnome.org/show_bug.cgi?id=752962

2 files changed, 52 insertions, 6 deletions

diff --git a/sys/v4l2/gstv4l2object.c b/sys/v4l2/gstv4l2object.c
index 0ec774ae4..8817f6987 100644
--- a/sys/v4l2/gstv4l2object.c
+++ b/sys/v4l2/gstv4l2object.c
@@ -3393,6 +3393,7 @@ gst_v4l2_object_set_format_full (GstV4l2Object * v4l2object, GstCaps * caps,
     gint stride = GST_VIDEO_INFO_PLANE_STRIDE (&info, 0);
 
     format.type = v4l2object->type;
+
     format.fmt.pix.width = width;
     format.fmt.pix.height = height;
     format.fmt.pix.pixelformat = pixelformat;
diff --git a/sys/v4l2/gstv4l2videodec.c b/sys/v4l2/gstv4l2videodec.c
index c7c795b68..8868d26b9 100644
--- a/sys/v4l2/gstv4l2videodec.c
+++ b/sys/v4l2/gstv4l2videodec.c
@@ -57,6 +57,8 @@ enum
 G_DEFINE_ABSTRACT_TYPE (GstV4l2VideoDec, gst_v4l2_video_dec,
     GST_TYPE_VIDEO_DECODER);
 
+static GstFlowReturn gst_v4l2_video_dec_finish (GstVideoDecoder * decoder);
+
 static void
 gst_v4l2_video_dec_set_property (GObject * object,
     guint prop_id, const GValue * value, GParamSpec * pspec)
@@ -245,7 +247,31 @@ gst_v4l2_video_dec_set_format (GstVideoDecoder * decoder,
     gst_video_codec_state_unref (self->input_state);
     self->input_state = NULL;
 
-    /* FIXME we probably need to do more work if pools are active */
+    gst_v4l2_video_dec_finish (decoder);
+    gst_v4l2_object_stop (self->v4l2output);
+
+    /* The renegotiation flow don't blend with the base class flow. To
+     * properly stop the capture pool we need to reclaim our buffers, which
+     * will happend through the allocation query. The allocation query is
+     * triggered by gst_video_decoder_negotiate() which requires the output
+     * caps to be set, but we can't know this information as we rely on the
+     * decoder, which requires the capture queue to be stopped.
+     *
+     * To workaround this issue, we simply run an allocation query with the
+     * old negotiated caps in order to drain/reclaim our buffers. That breaks
+     * the complexity and should not have much impact in performance since the
+     * following allocation query will happen on a drained pipeline and won't
+     * block. */
+    {
+      GstCaps *caps = gst_pad_get_current_caps (decoder->srcpad);
+      GstQuery *query = gst_query_new_allocation (caps, FALSE);
+      gst_pad_peer_query (decoder->srcpad, query);
+      gst_query_unref (query);
+      gst_caps_unref (caps);
+    }
+
+    gst_v4l2_object_stop (self->v4l2capture);
+    self->output_flow = GST_FLOW_OK;
   }
 
   ret = gst_v4l2_object_set_format (self->v4l2output, state->caps, &error);
@@ -279,12 +305,15 @@ gst_v4l2_video_dec_flush (GstVideoDecoder * decoder)
 
   self->output_flow = GST_FLOW_OK;
 
+  if (self->v4l2output->pool)
+    gst_v4l2_buffer_pool_flush (self->v4l2output->pool);
+
+  if (self->v4l2capture->pool)
+    gst_v4l2_buffer_pool_flush (self->v4l2capture->pool);
+
   gst_v4l2_object_unlock_stop (self->v4l2output);
   gst_v4l2_object_unlock_stop (self->v4l2capture);
 
-  gst_v4l2_buffer_pool_flush (self->v4l2output->pool);
-  gst_v4l2_buffer_pool_flush (self->v4l2capture->pool);
-
   return TRUE;
 }
 
@@ -379,10 +408,24 @@ gst_v4l2_video_dec_finish (GstVideoDecoder * decoder)
 
   GST_DEBUG_OBJECT (decoder, "Done draining buffers");
 
+  /* TODO Shall we cleanup any reffed frame to workaround broken decoders ? */
+
 done:
   return ret;
 }
 
+static gboolean
+gst_v4l2_video_dec_drain (GstVideoDecoder * decoder)
+{
+  GstV4l2VideoDec *self = GST_V4L2_VIDEO_DEC (decoder);
+
+  GST_DEBUG_OBJECT (self, "Draining...");
+  gst_v4l2_video_dec_finish (decoder);
+  gst_v4l2_video_dec_flush (decoder);
+
+  return TRUE;
+}
+
 static GstVideoCodecFrame *
 gst_v4l2_video_dec_get_oldest_frame (GstVideoDecoder * decoder)
 {
@@ -522,6 +565,7 @@ gst_v4l2_video_dec_handle_frame (GstVideoDecoder * decoder,
   GstFlowReturn ret = GST_FLOW_OK;
   gboolean processed = FALSE;
   GstBuffer *tmp;
+  GstTaskState task_state;
 
   GST_DEBUG_OBJECT (self, "Handling frame %d", frame->system_frame_number);
 
@@ -649,8 +693,8 @@ gst_v4l2_video_dec_handle_frame (GstVideoDecoder * decoder,
       goto activate_failed;
   }
 
-  if (gst_pad_get_task_state (GST_VIDEO_DECODER_SRC_PAD (self)) ==
-      GST_TASK_STOPPED) {
+  task_state = gst_pad_get_task_state (GST_VIDEO_DECODER_SRC_PAD (self));
+  if (task_state == GST_TASK_STOPPED || task_state == GST_TASK_PAUSED) {
     /* It's possible that the processing thread stopped due to an error */
     if (self->output_flow != GST_FLOW_OK &&
         self->output_flow != GST_FLOW_FLUSHING) {
@@ -949,6 +993,7 @@ gst_v4l2_video_dec_class_init (GstV4l2VideoDecClass * klass)
   video_decoder_class->stop = GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_stop);
   video_decoder_class->finish = GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_finish);
   video_decoder_class->flush = GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_flush);
+  video_decoder_class->drain = GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_drain);
   video_decoder_class->set_format =
       GST_DEBUG_FUNCPTR (gst_v4l2_video_dec_set_format);
   video_decoder_class->negotiate =