Dacast recommends against using VP9.
In particular, if you plan to do All Device (HTML5) live streaming it is recommended to use the H.264 video codec instead.
Live streaming can be done with VP9, but has known playback issues over certain environments. Use it at your own risk.
For more information on VP9, it’s a proprietary compression format that was developed by On2Technologies in May 2003. It is also called the TrueMotion video codec. It is a ‘lossy’ video compression format. It is often used by JavaFX, Adobe Flash and Flash Video Files.