msdk:dec: Add new propery to dump frames in decoded order

The new property "output-order" can be set to either "display" order
which is the default where frames will be outputting in display order,
or "decoded-order" which will be outputting the frames in decoded order.

The "decoded order" output is generally useful for debugging. But there
are few
customers who use it for low-latency streaming. For eg if the customer
already knows that the stream doesn't have b-frames (which means no
algorithm requires for display order calculation), then they can use
"decoded-order"
output to skip some of the DPB logic to avoid the frame accumulation at
start-up.

The root cause of the above issue is a bit of unclarity in h264 spec +
lazy implementation of many H264 encoders; This is well handled in
gstreamer-vaapi using "low-latency" property:
https://bugzilla.gnome.org/show_bug.cgi?id=762509

https://bugzilla.gnome.org/show_bug.cgi?id=795783

sys/msdk/gstmsdkdec.c

@@ -40,6 +40,7 @@
 #include "gstmsdkvideomemory.h"
 #include "gstmsdksystemmemory.h"
 #include "gstmsdkcontextutil.h"
+#include "msdk-enums.h"
 
 GST_DEBUG_CATEGORY_EXTERN (gst_msdkdec_debug);
 #define GST_CAT_DEFAULT gst_msdkdec_debug
@@ -61,10 +62,12 @@ enum
   PROP_0,
   PROP_HARDWARE,
   PROP_ASYNC_DEPTH,
+  PROP_OUTPUT_ORDER,
 };
 
 #define PROP_HARDWARE_DEFAULT            TRUE
 #define PROP_ASYNC_DEPTH_DEFAULT         1
+#define PROP_OUTPUT_ORDER_DEFAULT        GST_MSDKDEC_OUTPUT_ORDER_DISPLAY
 
 #define gst_msdkdec_parent_class parent_class
 G_DEFINE_TYPE (GstMsdkDec, gst_msdkdec, GST_TYPE_VIDEO_DECODER);
@@ -272,6 +275,10 @@ gst_msdkdec_init_decoder (GstMsdkDec * thiz)
   thiz->param.mfx.FrameInfo.ChromaFormat = MFX_CHROMAFORMAT_YUV420;
   thiz->param.mfx.FrameInfo.PicStruct = MFX_PICSTRUCT_PROGRESSIVE;
 
+  /* This is a deprecated attribute in msdk-2017 version, but some
+   * customers still using this for low-latency streaming of non-b-frame
+   * encoded streams */
+  thiz->param.mfx.DecodedOrder = thiz->output_order;
   /* allow subclass configure further */
   if (klass->configure) {
     if (!klass->configure (thiz))
@@ -1060,6 +1067,9 @@ gst_msdkdec_set_property (GObject * object, guint prop_id, const GValue * value,
     case PROP_ASYNC_DEPTH:
       thiz->async_depth = g_value_get_uint (value);
       break;
+    case PROP_OUTPUT_ORDER:
+      thiz->output_order = g_value_get_enum (value);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -1089,6 +1099,9 @@ gst_msdkdec_get_property (GObject * object, guint prop_id, GValue * value,
     case PROP_ASYNC_DEPTH:
       g_value_set_uint (value, thiz->async_depth);
       break;
+    case PROP_OUTPUT_ORDER:
+      g_value_set_enum (value, thiz->output_order);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -1144,6 +1157,13 @@ gst_msdkdec_class_init (GstMsdkDecClass * klass)
           1, 20, PROP_ASYNC_DEPTH_DEFAULT,
           G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
 
+  g_object_class_install_property (gobject_class, PROP_OUTPUT_ORDER,
+      g_param_spec_enum ("output-order", "DecodedFramesOutputOrder",
+          "Decoded frames output order",
+          gst_msdkdec_output_order_get_type (),
+          PROP_OUTPUT_ORDER_DEFAULT,
+          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
   gst_element_class_add_static_pad_template (element_class, &src_factory);
 }
 
@@ -1156,6 +1176,7 @@ gst_msdkdec_init (GstMsdkDec * thiz)
   thiz->tasks = g_array_new (FALSE, TRUE, sizeof (MsdkDecTask));
   thiz->hardware = PROP_HARDWARE_DEFAULT;
   thiz->async_depth = PROP_ASYNC_DEPTH_DEFAULT;
+  thiz->output_order = PROP_OUTPUT_ORDER_DEFAULT;
   thiz->is_packetized = TRUE;
   thiz->adapter = gst_adapter_new ();
 }

sys/msdk/gstmsdkdec.h

@@ -86,6 +86,7 @@ struct _GstMsdkDec
   /* element properties */
   gboolean hardware;
   guint async_depth;
+  guint output_order;
 };
 
 struct _GstMsdkDecClass

sys/msdk/msdk-enums.c

@@ -33,6 +33,26 @@
 
 #include "msdk-enums.h"
 
+/*========= MSDK Decoder Enums =========================*/
+GType
+gst_msdkdec_output_order_get_type (void)
+{
+  static GType type = 0;
+
+  static const GEnumValue values[] = {
+    {GST_MSDKDEC_OUTPUT_ORDER_DISPLAY, "Output frames in Display order",
+        "display"},
+    {GST_MSDKDEC_OUTPUT_ORDER_DECODE, "Output frames in Decoded order",
+        "decoded"},
+    {0, NULL, NULL}
+  };
+
+  if (!type) {
+    type = g_enum_register_static ("GstMsdkDecOutputOrder", values);
+  }
+  return type;
+}
+
 /*========= MSDK Encoder Enums =========================*/
 GType
 gst_msdkenc_rate_control_get_type (void)

sys/msdk/msdk-enums.h

@@ -40,6 +40,16 @@ G_BEGIN_DECLS
 
 #define _MFX_TRELLIS_NONE    0
 
+/*========= MSDK Decoder Enums =========================*/
+typedef enum
+{
+  GST_MSDKDEC_OUTPUT_ORDER_DISPLAY = 0,
+  GST_MSDKDEC_OUTPUT_ORDER_DECODE,
+} GstMskdDecOutputOrder;
+
+GType
+gst_msdkdec_output_order_get_type (void);
+
 /*========= MSDK Encoder Enums =========================*/
 GType
 gst_msdkenc_rate_control_get_type (void);