libs: encoder: h265: support I/P/B QP setting seperatedly

Creates 2 properties, qp-ip and qp-ib for setting different QP for P/B
frames
and set slice_qp_delta for each frame according to the value provided.

https://bugzilla.gnome.org/show_bug.cgi?id=785923

gst-libs/gst/vaapi/gstvaapiencoder_h265.c

@@ -100,6 +100,8 @@ struct _GstVaapiEncoderH265
   guint32 init_qp;
   guint32 min_qp;
   guint32 qp_i;
+  guint32 qp_ip;
+  guint32 qp_ib;
   guint32 num_slices;
   guint32 num_bframes;
   guint32 ctu_width;            /* CTU == Coding Tree Unit */
@@ -1723,6 +1725,21 @@ add_slice_headers (GstVaapiEncoderH265 * encoder, GstVaapiEncPicture * picture,
 
     slice_param->max_num_merge_cand = 5;        /* MaxNumMergeCand  */
     slice_param->slice_qp_delta = encoder->qp_i - encoder->init_qp;
+    if (GST_VAAPI_ENCODER_RATE_CONTROL (encoder) == GST_VAAPI_RATECONTROL_CQP) {
+      if (picture->type == GST_VAAPI_PICTURE_TYPE_P) {
+        slice_param->slice_qp_delta += encoder->qp_ip;
+      } else if (picture->type == GST_VAAPI_PICTURE_TYPE_B) {
+        slice_param->slice_qp_delta += encoder->qp_ib;
+      }
+      if ((gint) encoder->init_qp + slice_param->slice_qp_delta <
+          (gint) encoder->min_qp) {
+        slice_param->slice_qp_delta = encoder->min_qp - encoder->init_qp;
+      }
+      /* TODO: max_qp could be provided as a property in the future */
+      if ((gint) encoder->init_qp + slice_param->slice_qp_delta > 51) {
+        slice_param->slice_qp_delta = 51 - encoder->init_qp;
+      }
+    }
 
     slice_param->slice_fields.bits.
         slice_loop_filter_across_slices_enabled_flag = TRUE;
@@ -2543,6 +2560,12 @@ gst_vaapi_encoder_h265_set_property (GstVaapiEncoder * base_encoder,
     case GST_VAAPI_ENCODER_H265_PROP_MIN_QP:
       encoder->min_qp = g_value_get_uint (value);
       break;
+    case GST_VAAPI_ENCODER_H265_PROP_QP_IP:
+      encoder->qp_ip = g_value_get_int (value);
+      break;
+    case GST_VAAPI_ENCODER_H265_PROP_QP_IB:
+      encoder->qp_ib = g_value_get_int (value);
+      break;
     case GST_VAAPI_ENCODER_H265_PROP_NUM_SLICES:
       encoder->num_slices = g_value_get_uint (value);
       break;
@@ -2655,6 +2678,32 @@ gst_vaapi_encoder_h265_get_default_properties (void)
           "Minimum QP", "Minimum quantizer value", 1, 51, 1,
           G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
 
+  /**
+   * GstVaapiEncoderH265:qp-ip:
+   *
+   * The difference of QP between I and P Frame.
+   * This is available only on CQP mode.
+   */
+  GST_VAAPI_ENCODER_PROPERTIES_APPEND (props,
+      GST_VAAPI_ENCODER_H265_PROP_QP_IP,
+      g_param_spec_int ("qp-ip",
+          "Difference of QP between I and P frame",
+          "Difference of QP between I and P frame (available only on CQP)",
+          -51, 51, 0, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
+  /**
+   * GstVaapiEncoderH265:qp-ib:
+   *
+   * The difference of QP between I and B Frame.
+   * This is available only on CQP mode.
+   */
+  GST_VAAPI_ENCODER_PROPERTIES_APPEND (props,
+      GST_VAAPI_ENCODER_H265_PROP_QP_IB,
+      g_param_spec_int ("qp-ib",
+          "Difference of QP between I and B frame",
+          "Difference of QP between I and B frame (available only on CQP)",
+          -51, 51, 0, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
   /* FIXME: there seems to be issues with multi-slice encoding */
   /**
    * GstVaapiEncoderH265:num-slices:

gst-libs/gst/vaapi/gstvaapiencoder_h265.h

@@ -43,6 +43,8 @@ typedef struct _GstVaapiEncoderH265 GstVaapiEncoderH265;
  * @GST_VAAPI_ENCODER_H265_PROP_NUM_REF_FRAMES: Maximum number of reference frames.
  * @GST_VAAPI_ENCODER_H265_PROP_CPB_LENGTH: Length of the CPB buffer
  * @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.
  *   in milliseconds (uint).
  *
  * The set of H.265 encoder specific configurable properties.
@@ -55,6 +57,8 @@ typedef enum {
   GST_VAAPI_ENCODER_H265_PROP_NUM_REF_FRAMES = -5,
   GST_VAAPI_ENCODER_H265_PROP_CPB_LENGTH = -7,
   GST_VAAPI_ENCODER_H265_PROP_MBBRC = -8,
+  GST_VAAPI_ENCODER_H265_PROP_QP_IP = -9,
+  GST_VAAPI_ENCODER_H265_PROP_QP_IB = -10,
 } GstVaapiEncoderH265Prop;
 
 GstVaapiEncoder *