libvpx: Pull from upstream

source/libvpx/vpx/vp8cx.h

Index: source/libvpx/vpx/vp8cx.h
===================================================================
--- source/libvpx/vpx/vp8cx.h	(revision 254565)
+++ source/libvpx/vpx/vp8cx.h	(working copy)
@@ -195,6 +195,11 @@
 
   VP9E_SET_SVC,
   VP9E_SET_SVC_PARAMETERS,
+  /*!\brief control function to set svc layer for spatial and temporal.
+   * \note Valid ranges: 0..#vpx_codec_enc_cfg::ss_number_layers for spatial
+   *                     layer and 0..#vpx_codec_enc_cfg::ts_number_layers for
+   *                     temporal layer.
+   */
   VP9E_SET_SVC_LAYER_ID
 };
 
@@ -297,9 +302,16 @@
   int alt_fb_idx;             /**< alt reference frame frame buffer index */
 } vpx_svc_parameters_t;
 
+/*!\brief  vp9 svc layer parameters
+ *
+ * This defines the spatial and temporal layer id numbers for svc encoding.
+ * This is used with the #VP9E_SET_SVC_LAYER_ID control to set the spatial and
+ * temporal layer id for the current frame.
+ *
+ */
 typedef struct vpx_svc_layer_id {
-  int spatial_layer_id;
-  int temporal_layer_id;
+  int spatial_layer_id;       /**< Spatial layer id number. */
+  int temporal_layer_id;      /**< Temporal layer id number. */
 } vpx_svc_layer_id_t;
 
 /*!\brief VP8 encoder control function parameter type