From 2fce126cc7968246ce4d0602052d62b12e4662b9 Mon Sep 17 00:00:00 2001
From: Wangfei <fei.w.wang@intel.com>
Date: Thu, 30 Aug 2018 11:08:07 +0800
Subject: [PATCH] libs: encoder: h265: add low delay B frame support.

Low delay B frame provide the function of transforming
P frame into low delay B frame which frame type is B, but
only reference predictive frames. This can be used when P
frame unsupported. Especially for P and B both unsupported,
in this case, I and low delay B frame can be encoded in a
stream.

https://bugzilla.gnome.org/show_bug.cgi?id=796984
---
 gst-libs/gst/vaapi/gstvaapiencoder_h265.c | 27 +++++++++++++++++++++++
 gst-libs/gst/vaapi/gstvaapiencoder_h265.h |  2 ++
 2 files changed, 29 insertions(+)

diff --git a/gst-libs/gst/vaapi/gstvaapiencoder_h265.c b/gst-libs/gst/vaapi/gstvaapiencoder_h265.c
index e1814d24b1..1348e64b94 100644
--- a/gst-libs/gst/vaapi/gstvaapiencoder_h265.c
+++ b/gst-libs/gst/vaapi/gstvaapiencoder_h265.c
@@ -110,6 +110,7 @@ struct _GstVaapiEncoderH265
   guint32 luma_height;
   GstClockTime cts_offset;
   gboolean config_changed;
+  gboolean low_delay_b;
 
   /* maximum required size of the decoded picture buffer */
   guint32 max_dec_pic_buffering;
@@ -1684,6 +1685,9 @@ add_slice_headers (GstVaapiEncoderH265 * encoder, GstVaapiEncPicture * picture,
     }
     slice_param->num_ctu_in_slice = cur_slice_ctus;
     slice_param->slice_type = h265_get_slice_type (picture->type);
+    if (encoder->low_delay_b && slice_param->slice_type == GST_H265_P_SLICE) {
+      slice_param->slice_type = GST_H265_B_SLICE;
+    }
     slice_param->slice_pic_parameter_set_id = 0;
 
     slice_param->slice_fields.bits.num_ref_idx_active_override_flag =
@@ -1717,6 +1721,13 @@ add_slice_headers (GstVaapiEncoderH265 * encoder, GstVaapiEncPicture * picture,
             GST_VAAPI_SURFACE_PROXY_SURFACE_ID (reflist_1[i_ref]->pic);
         slice_param->ref_pic_list1[i_ref].pic_order_cnt = reflist_1[i_ref]->poc;
       }
+    } else if (picture->type == GST_VAAPI_PICTURE_TYPE_P
+        && encoder->low_delay_b) {
+      for (; i_ref < reflist_0_count; ++i_ref) {
+        slice_param->ref_pic_list1[i_ref].picture_id =
+            GST_VAAPI_SURFACE_PROXY_SURFACE_ID (reflist_0[i_ref]->pic);
+        slice_param->ref_pic_list1[i_ref].pic_order_cnt = reflist_0[i_ref]->poc;
+      }
     }
     for (; i_ref < G_N_ELEMENTS (slice_param->ref_pic_list1); ++i_ref) {
       slice_param->ref_pic_list1[i_ref].picture_id = VA_INVALID_SURFACE;
@@ -2583,6 +2594,10 @@ gst_vaapi_encoder_h265_set_property (GstVaapiEncoder * base_encoder,
     case GST_VAAPI_ENCODER_H265_PROP_MBBRC:
       encoder->mbbrc = g_value_get_enum (value);
       break;
+    case GST_VAAPI_ENCODER_H265_PROP_LOW_DELAY_B:
+      encoder->low_delay_b = g_value_get_boolean (value);
+      break;
+
     default:
       return GST_VAAPI_ENCODER_STATUS_ERROR_INVALID_PARAMETER;
   }
@@ -2748,6 +2763,18 @@ gst_vaapi_encoder_h265_get_default_properties (void)
           GST_VAAPI_TYPE_ENCODER_MBBRC, GST_VAAPI_ENCODER_MBBRC_AUTO,
           G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
 
+  /**
+   * GstVaapiEncoderH265:low_delay_b:
+   *
+   * Enable low delay b frame, which will change P frame with B frame.
+   */
+  GST_VAAPI_ENCODER_PROPERTIES_APPEND (props,
+      GST_VAAPI_ENCODER_H265_PROP_LOW_DELAY_B,
+      g_param_spec_boolean ("low-delay-b",
+          "Enable low delay b",
+          "Transforms P frames into predictive B frames. Enable it when P frames are not supported.",
+          FALSE, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
   return props;
 }
 
diff --git a/gst-libs/gst/vaapi/gstvaapiencoder_h265.h b/gst-libs/gst/vaapi/gstvaapiencoder_h265.h
index 3496742a30..e53881050f 100644
--- a/gst-libs/gst/vaapi/gstvaapiencoder_h265.h
+++ b/gst-libs/gst/vaapi/gstvaapiencoder_h265.h
@@ -45,6 +45,7 @@ typedef struct _GstVaapiEncoderH265 GstVaapiEncoderH265;
  * @GST_VAAPI_ENCODER_H265_PROP_MBBRC: Macroblock level Bitrate Control.
  * @GST_VAAPI_ENCODER_H265_PROP_QP_IP: Difference of QP between I and P frame.
  * @GST_VAAPI_ENCODER_H265_PROP_QP_IB: Difference of QP between I and B frame.
+ * @GST_VAAPI_ENCODER_H265_PROP_LOW_DELAY_B: use low delay b feature.
  *   in milliseconds (uint).
  *
  * The set of H.265 encoder specific configurable properties.
@@ -59,6 +60,7 @@ typedef enum {
   GST_VAAPI_ENCODER_H265_PROP_MBBRC = -8,
   GST_VAAPI_ENCODER_H265_PROP_QP_IP = -9,
   GST_VAAPI_ENCODER_H265_PROP_QP_IB = -10,
+  GST_VAAPI_ENCODER_H265_PROP_LOW_DELAY_B = -11,
 } GstVaapiEncoderH265Prop;
 
 GstVaapiEncoder *