AIT

Description
The Application Information Table describes the applications and related information. The AIT has a general descriptor loop that provides common information about the applications. Each application in the application loop has its own descriptor loop for application-specific descriptors.
TR 101 290
  • The repetition rate must be less than 10 seconds for the AIT
  • The time between receiving the last byte of the section and the first byte of the next section should be at least 25 ms.
  • The Scrambling Control must have the binary value '00' (umscrambled)
  • Descriptors
    The following descriptors may appear in the AIT :
  • Application descriptor
  • Application name descriptor
  • Application icons descriptor
  • External application authorisation descriptor
  • Transport protocol descriptor
  • IP signalling descriptor
  • Pre-fetch descriptor
  • DII location descriptor
  • DVB-J application descriptor
  • DVB-J application location descriptor
  • DVB-HTML application descriptor
  • DVB-HTML application location descriptor
  • DVB-HTML application boundary descriptor

  • name bits description
    AIT
    Table ID 8 Indicates to which table this section belongs, in this case AIT (0x74)
    section_syntax_indicator 1 Indicates whether a sub-table structure including CRC check is used.
    reserved_for_future_use 1 always binary value '0'
    Reserved 2 always binary value '11'
    Section length 12 The length of the section in bytes. This length starts immediately after this field and includes the CRC.
    Test application flag 1 Indicates test application
    Application type 15 This 15-bit field indicates the type of application.
    Reserved 2 always binary value '11'
    version_number 5 Value between 0 to 31.
    A higher value indicates that the information has changed.
    current_next_indicator 1 This is to indicate whether a section is 'valid now' or 'valid in future'
    section_number 8 Value between 0x00 - 0xFF. Used to indicate the sections of a table. Up to 256 sections.
    last_section_number 8 The number of the last section, so the receiver know when the table is completely received.
    reserved for future use 4 always binary value '1111'
    common_descriptors_length 4 The length of the Common Descriptors
    reserved 4 always binary value '1111'
    Application loop length 12 The length of the Application loop
    Application Loop
    Application identifier 48 This 48 bit field identifies the application according to the following structure :
  • 32 bits organisation id.
  • 16 bits application id.
    The organization ID is a unique number found in ETSI TR 101 162.
  • Application control code 8 This field indicates the status of the application, and is dependent on the type of application.
    reserved for future use 4 always binary value '1111'
    Application descriptors loop length 12 The length of the application descriptors loop
    Application descriptors loop
    CRC_32 32 Cyclic redundancy check