libs: encoder: add target-percentage property

Allow users to set the target-percentage for
variable rate controls.  The default value is
70 (as hard-coded prior).

v2: minimum allowed value changed from 0 to 1
v3: target-percentage unchanged if CBR used

Resolves #129

gst-libs/gst/vaapi/gstvaapiencoder.c

@@ -145,8 +145,6 @@ gst_vaapi_encoder_properties_get_default (const GstVaapiEncoderClass * klass)
    *          else minimum bitrate = maximum bitrate * (2 * target percentage -100) / 100
    *      Target bitrate will be calculated like the following in the driver.
    *          target bitrate = maximum bitrate * target percentage / 100
-   *
-   * Note that target percentage is set as 70 currently in GStreamer VA-API.
    */
   GST_VAAPI_ENCODER_PROPERTIES_APPEND (props,
       GST_VAAPI_ENCODER_PROP_BITRATE,
@@ -155,6 +153,18 @@ gst_vaapi_encoder_properties_get_default (const GstVaapiEncoderClass * klass)
           "The desired bitrate expressed in kbps (0: auto-calculate)",
           0, 100 * 1024, 0, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
 
+  /**
+   * GstVaapiEncoder:target-percentage:
+   *
+   * The desired target percentage of bitrate for variable rate controls.
+   */
+  GST_VAAPI_ENCODER_PROPERTIES_APPEND (props,
+      GST_VAAPI_ENCODER_PROP_TARGET_PERCENTAGE,
+      g_param_spec_uint ("target-percentage",
+          "Target Percentage",
+          "The desired target percentage of bitrate for variable rate "
+          "controls.", 1, 100, 70, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
   /**
    * GstVaapiEncoder:keyframe-period:
    *
@@ -1035,7 +1045,7 @@ gst_vaapi_encoder_reconfigure_internal (GstVaapiEncoder * encoder)
 
   target_percentage =
       (GST_VAAPI_ENCODER_RATE_CONTROL (encoder) == GST_VAAPI_RATECONTROL_CBR) ?
-      100 : 70;
+      100 : encoder->target_percentage;
 
   /* *INDENT-OFF* */
   /* Default values for rate control parameter */
@@ -1199,6 +1209,10 @@ set_property (GstVaapiEncoder * encoder, gint prop_id, const GValue * value)
       status = gst_vaapi_encoder_set_bitrate (encoder,
           g_value_get_uint (value));
       break;
+    case GST_VAAPI_ENCODER_PROP_TARGET_PERCENTAGE:
+      status = gst_vaapi_encoder_set_target_percentage (encoder,
+          g_value_get_uint (value));
+      break;
     case GST_VAAPI_ENCODER_PROP_KEYFRAME_PERIOD:
       status = gst_vaapi_encoder_set_keyframe_period (encoder,
           g_value_get_uint (value));
@@ -1368,6 +1382,28 @@ gst_vaapi_encoder_set_bitrate (GstVaapiEncoder * encoder, guint bitrate)
   return GST_VAAPI_ENCODER_STATUS_SUCCESS;
 }
 
+GstVaapiEncoderStatus
+gst_vaapi_encoder_set_target_percentage (GstVaapiEncoder * encoder,
+    guint target_percentage)
+{
+  g_return_val_if_fail (encoder != NULL, 0);
+
+  if (encoder->target_percentage != target_percentage
+      && encoder->num_codedbuf_queued > 0) {
+    if (GST_VAAPI_ENCODER_RATE_CONTROL (encoder) != GST_VAAPI_RATECONTROL_CBR) {
+      GST_INFO ("Target percentage is changed to %d on runtime",
+          target_percentage);
+      encoder->target_percentage = target_percentage;
+      return gst_vaapi_encoder_reconfigure_internal (encoder);
+    }
+    GST_WARNING ("Target percentage is ignored for CBR rate-control");
+    return GST_VAAPI_ENCODER_STATUS_SUCCESS;
+  }
+
+  encoder->target_percentage = target_percentage;
+  return GST_VAAPI_ENCODER_STATUS_SUCCESS;
+}
+
 /**
  * gst_vaapi_encoder_set_keyframe_period:
  * @encoder: a #GstVaapiEncoder

gst-libs/gst/vaapi/gstvaapiencoder.h

@@ -114,6 +114,8 @@ typedef enum {
  * GstVaapiEncoderProp:
  * @GST_VAAPI_ENCODER_PROP_RATECONTROL: Rate control (#GstVaapiRateControl).
  * @GST_VAAPI_ENCODER_PROP_BITRATE: Bitrate expressed in kbps (uint).
+ * @GST_VAAPI_ENCODER_PROP_TARGET_PERCENTAGE: Desired target percentage of
+ *  bitrate for variable rate controls.
  * @GST_VAAPI_ENCODER_PROP_KEYFRAME_PERIOD: The maximal distance
  *   between two keyframes (uint).
  * @GST_VAAPI_ENCODER_PROP_TUNE: The tuning options (#GstVaapiEncoderTune).
@@ -126,6 +128,7 @@ typedef enum {
 typedef enum {
   GST_VAAPI_ENCODER_PROP_RATECONTROL = 1,
   GST_VAAPI_ENCODER_PROP_BITRATE,
+  GST_VAAPI_ENCODER_PROP_TARGET_PERCENTAGE,
   GST_VAAPI_ENCODER_PROP_KEYFRAME_PERIOD,
   GST_VAAPI_ENCODER_PROP_TUNE,
   GST_VAAPI_ENCODER_PROP_QUALITY_LEVEL,
@@ -180,6 +183,10 @@ gst_vaapi_encoder_set_rate_control (GstVaapiEncoder * encoder,
 GstVaapiEncoderStatus
 gst_vaapi_encoder_set_bitrate (GstVaapiEncoder * encoder, guint bitrate);
 
+GstVaapiEncoderStatus
+gst_vaapi_encoder_set_target_percentage (GstVaapiEncoder * encoder,
+    guint target_percentage);
+
 GstVaapiEncoderStatus
 gst_vaapi_encoder_put_frame (GstVaapiEncoder * encoder,
     GstVideoCodecFrame * frame);

gst-libs/gst/vaapi/gstvaapiencoder_priv.h

@@ -262,6 +262,7 @@ struct _GstVaapiEncoder
   GstVaapiRateControl rate_control;
   guint32 rate_control_mask;
   guint bitrate; /* kbps */
+  guint target_percentage;
   guint keyframe_period;
 
   /* Maximum number of reference frames supported