Log Message:
libvpx: updated to 1.8.0

v1.8.0 "Northern Shoveler Duck"
  This release focused on encoding performance for realtime and VOD use cases.

  - Upgrading:
    This adds and improves several vp9 controls. Most are related to SVC:
      VP9E_SET_SVC_FRAME_DROP_LAYER:
        - Frame dropping in SVC.
      VP9E_SET_SVC_INTER_LAYER_PRED:
        - Inter-layer prediction in SVC.
      VP9E_SET_SVC_GF_TEMPORAL_REF:
        - Enable long term temporal reference in SVC.
      VP9E_SET_SVC_REF_FRAME_CONFIG/VP9E_GET_SVC_REF_FRAME_CONFIG:
        - Extend and improve this control for better flexibility in setting SVC
          pattern dynamically.
      VP9E_SET_POSTENCODE_DROP:
        - Allow for post-encode frame dropping (applies to non-SVC too).
      VP9E_SET_SVC_SPATIAL_LAYER_SYNC:
        - Enable spatial layer sync frames.
      VP9E_SET_SVC_LAYER_ID:
        - Extend api to specify temporal id for each spatial layers.
      VP9E_SET_ROI_MAP:
        - Extend Region of Interest functionality to VP9.

  - Enhancements:
    2 pass vp9 encoding has improved substantially. When using --auto-alt-ref=6,
    we see approximately 8% for VBR and 10% for CQ. When using --auto-alt-ref=1,
    the gains are approximately 4% for VBR and 5% for CQ.

    For real-time encoding, speed 7 has improved by ~5-10%. Encodes targeted at
    screen sharing have improved when the content changes significantly (slide
    sharing) or scrolls. There is a new speed 9 setting for mobile devices which
    is about 10-20% faster than speed 8.

  - Bug fixes:
    VP9 denoiser issue.
    VP9 partition issue for 1080p.
    VP9 rate control improvments.
    Postprocessing Multi Frame Quality Enhancement (MFQE) issue.
    VP8 multithread decoder issues.
    A variety of fuzzing issues.