WebM VP9 and VP8 in front, HLS with VP9-in-MP4 video with Opus-in-MP4 or AAC audio behind.
HLS VP9+Opus or VP9+MP3, no fallbacks:
HLS VP9+Opus or VP9+MP3, with h.264 fallback:
HLS VP9 in fMP4:
HLS h.264 in fMP4:
HLS Opus in fMP4:
HLS AAC in fMP4:
HLS MP3: