Video type parameters
<video> element allows UA capability-based fallback with multiple alternative video resources designated by multiple
<source> elements. The UA is expected to pick the alternative it tries to play by comparing the information given in the
type attribute against its knowledge about its own playback capabilities.
The main media type designates the container format. In general, it does not say anything about codecs needed to decode the streams packaged in the container. RFC 4281 defines a
codecs MIME parameter for indicating which codecs are used within the container. The parameter takes a double-quoted comma-separated list of codec identifiers.