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2.2.3.6 $M (Metadata) Packet

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The $M (Metadata) packet is used by the server to transfer metadata for the current playlist entry to the client.

The playlist-gen-id parameter in the $M packet MUST specify the identifier of the playlist entry that is described by the $M packet. The playlist-gen-id parameter is specified in section 2.2.1.4.18.

The value of the broadcast-id parameter in the $M packet MUST uniquely identify the source of "live" content within the scope of the current server-side playlist. For example, if the same live content source is used in multiple entries in a single playlist, the value of the broadcast-id parameter will be the same in each of those entries. There is no requirement that the values of the broadcast-id parameter be unique across different server-side playlists. If a playlist entry is not using a live content source, the value of the broadcast-id parameter MUST be 0.

The features parameter in the $M packet MUST specify the properties and capabilities of the playlist entry that is described by the $M packet. The features parameter is specified in section 2.2.1.4.8.

The $M packet starts with a Framing Header (section 2.2.3.1.1) followed by an MMS data packet (section 2.2.3.1.2), with the following additional details:

B (1 bit): As specified in section 2.2.3.1.1.

Frame (7 bits): As specified in section 2.2.3.1.1.

PacketID (1 byte): This field MUST be set to the character "M" (0x4D).

PacketLength (2 bytes): As specified in section 2.2.3.1.1.

Reason (4 bytes): This field MUST NOT be present.

Payload (variable): The field MUST adhere to the ABNF syntax for Metadata-Payload, defined as follows:

 Metadata-Payload = playlist-gen-id             ; section 2.2.1.4.18
                    "," SP
                    "broadcast-id=" 1*10DIGIT
                    "," SP
                    features                    ; section 2.2.1.4.8
                    %x00
                    *content-description-list   ; section 2.2.4

The value of the broadcast-id parameter MUST be an integer in the range from 0 through 4,294,967,295.