The portion refers to the AV1 (AOMedia Video 1) codec, a royalty-free format designed to deliver high-quality video while using significantly less data than previous standards like H.264 or VP9. av01 : The identifier for the AV1 video codec.
| Token | Meaning | |-------------|-------------------------------------------------------------------------| | av01008m08 | Custom or experimental codec identifier. Possibly internal to a specific player/encoder. | | 399 | Likely or stream label. | | opus | Opus audio codec (RFC 6716). | | 251 | WebM/Matroska codec ID for Opus (used in DASH/WebM manifests). | | new | Flag indicating a newer encoding profile or replacement track. | codecs av01008m08 399 opus 251 new
Example DASH usage: