[ATAC 3.0] MA3 Message

7.2.3.1 mmt_atsc3_message() MMT Signaling Message

An MMT Signaling message mmt_atac3_message() is defined to deliver information specific to ATAC 3.0 service.

The value of 0x8100 in the range of user private use shall be assigned for the message_id of mmt_atac3_message() as per subclause 9.7 of ISO/IEC 23008-1[36]. The syntax of this message shall be as provided in Table 7.6

The text following Table 7.6 shall describe the semantics of each field in mmt_atac3_message().

Syntax	No. of Bits	Format
mmt_atac3_message() {     message_id     version     length     message payload {         service_id         atac3_message_content_type         atac3_message_content_version         atac3_message_content_compression         URI_length         for(i=0 ; i<URI_length; i++) {             URI_byte;         }         atac3_message_content_length         for(i=0; i<atac3_message_content_length; i++) {             atac3_message_content_byte         }         for(i=0; i < length-11-URI_length-atac3_message_content_length) {             reserved         } }	16 8 32 16 16 8 8 8 8 32 8   8

message_id – A 16-bit unsigned integer field that shall uniquely identify the mmt_atsc3_message(). The value of this field shall be 0x8100.

version – An 8-bit unsigned integer field that shall be incremented by 1 any time there is a change in the information carried in this message. When the version field reaches its maximum value of 255, its value shall wraparound to 0.

length –A 32-bit unsigned integer field that shall provide the length of mmt_atsc3_message() in bytes, counting from the beginning of the next field to the last byte of the mmt_atsc3_message().

service_id – A 16-bit unsigned integer field that shall associate the message payload with the service identified in the serviceId attribute given in the SLT.

atsc3_message_content_type – A 16-bit unsigned integer field that shall uniquely identify the typeof message content in the mmt_atsc3_message() payload, coded per Table 7.7 below.

Table 7.7 Code Values for atsc3_message_content_type

atac3_message_content_type Meaning
0x0000	Reserved
0x0001	userServiceDescription as given in Table 7.5
0x0002	MPD as given in MPEG DASH [58].
0x0003	Application Signalling Table as given in A/337, Application Signaling and Triggers[48].
0x0004	Application Event Information as given in A/337, Application Signaling and Triggers[48].
0x0005	Video Stream Properties Descriptor (Sec. 7.2.3.2)
0x0006	ATSC Staggercast Descriptor (Sec. 7.2.3.3)
0x0007	Inband Event Descriptor as given in A/337, Application Signaling and Triggers [48].
0x0008	Caption Asset Descriptor (Sec. 7.2.3.5)
0x0009	Audio Stream Properties Descriptor (Sec. 7.2.3.4)
0x000A~0xFFFF	Reserved for future use

atsc3_message_content_version – An 8-bit unsigned integer field that shall be incremented by 1 any time there is a change in the mmt_atsc3_message content identified by a service_id, and atsc_message_content_type pair and URI if present. When the atsc3_message_content_version field reaches its maximum value, its value shall wrap around to 0.

atsc3_message_content_compression – An 8-bit unsigned integer field that shall identify the type of compression applied to the data in atsc3_message_content_byte.

atac3_message_content_compression Meaning
0x00	Reserved
0x01	No Compression has been applied
0x02	gzip specified in RFC 1952[15] has been applied
0x03	The template-based compression scheme as specified in Annex D has been applied
0x04~0xFF	Reserved for future use

URI_length – An 8-bit unsigned integer field that shall provide the length of the URI uniquely identifying the message payload across services. If the URI is not present, the value of this field shall be set to 0.

URI_byte – An 8-bit unsigned integer field that shall contain a UTF-8 character of the URI associated with the content carried by this message excluding the terminating null character, as per RFC 3986 [19]. This field when present shall be used to identify delivered message payloads. The URI can be used by system tables to reference tables made available by delivered message payloads.

atsc3_message_content_length – A 32-bit unsigned integer field that shall provide the length of the content carried by this message.

atsc3_message_content_byte – An 8-bit unsigned integer field that shall contain a byte of the content carried by this message.