Atsc working Draft Template
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- Table length extensions
- Descriptor length extensions
- New descriptor types
Standard table types – As indicated in Table 4.2,
table_id values in the range 0xCE to 0xD2, 0xD5 to 0xDF and 0xE6-0xFE shall be reserved for use either when revising this PSIP Standard, or when another standard is issued. Protocol version field – Future substantive structural modifications shall be accommodated by defining different protocol version numbers. Backwards compatible additions or modifications may be added without incrementing the protocol version number. Table length extensions – Future amendments to this Standard may include new fields at the ends of certain tables. Tables that may be extensible in this way include those in which the last byte of the field just preceding the CRC may be determined without use of the section_length field. Such an extension is a backwards compatible addition. Descriptor length extensions – Future amendments to this Standard may include new fields at the ends of certain descriptors. Descriptors extensible in this way include those in which the last byte of the last currently defined field may be determined without the use of the descriptor_length field. 14 ATSC A/65:2013 Program and System Information Protocol 7 August 2013 New descriptor types– Future amendments to this Standard may define new types of descriptors not recognized or supported by existing receiving devices. A descriptor whose descriptor_tag identifies a type not recognized by a particular receiver is expected to be ignored. Descriptors can be included in certain specified places within PSIP tables, subject to certain restrictions (see Table 6.25). Descriptors may be used to extend data represented as fixed fields within the tables. They make the protocol very flexible since they can be included only as needed. New descriptor types can be standardized and included without affecting receivers that have not been designed to recognize and process the new types. 3.2.3 User Private Ranges Certain fields in this Standard are defined to include “user private” ranges: • table_id values in the range 0x40 through 0xBF • MGT table_type values in the range 0x0400 through 0x0FFF Table sections with table_id values in the user private range (0x40 through 0xBF) shall not appear in transport packets identified with the base_PID PID value (0x1FFB) 4 . The MGT may refer to private table sections with any value of table_id including values in the user private range. Refer to Section 6.2 for a discussion of the use of the MPEG-2 Registration Descriptor in the MGT. 3.3 Acronyms and Abbreviations The following acronyms and abbreviations are used within this document: Download 4.82 Kb. Do'stlaringiz bilan baham: |
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