The spec (https://storage.googleapis.com/downloads.webmproject.org/docs/vp9/vp-codec-iso-media-file-format-binding-20160516-draft.pdf) defines 8 fields: 
<sample entry 4CC>.<profile>.<level>.<bitDepth>.<colorSpace>.<chromaSubsampling>.<transferFunction>.<videoFullRangeFlag>

We currently require all fields to be present but does not validate if the specific field / value is supported. This is also not compliant to the current spec which allows missing fields.

We need to fix and finalize the spec and the code.