We are guaranteed to have VPX_IMG_FMT_I420, VPX_PLANE_Y, VPX_PLANE_U and VPX_PLANE_V as we require libvpx > 1.1.0. https://bugzilla.gnome.org/show_bug.cgi?id=739476
https://bugzilla.gnome.org/show_bug.cgi?id=687520
This is using libvpx, which can support more codecs than just VP8 and will likely support future codecs.