The PR merged in HLS-5
simplify something I've been debating implementing for a while.
If the script is configured to accept a comma seperated list of bitrates, we can generate multiple bitrate HLS streams and then create a top level playlist pointing to the relevant m3u8s.
Players that support adaptive streaming can then choose (and switch between) playlists in response to changing network conditions (e.g. going from wifi to 3G).