ANSI SCTE-128-2010 pdf download AVC Video Systems and Transport Constraints for Cable Television
6.3.2 Descriptors
6.3.2.1 Video descriptor AVC video is signaled by the AVC_video_descriptor() when required by ISO/IEC 13818-1[3] or as otherwise appropriate. This descriptor, when carried, shall be placed in the descriptor loop for the video program element of the PMT with a descriptor tag value of 0x28. Certain services may include video elementary streams that contain one or more AVC still pictures that conform to the still picture model of ISO/IEC 13818-1 [3]. Any elementary stream containing still pictures shall include a AVC_video_descriptor() with AVC_still_present_flag set to “1” in accordance with section 2.6.64 of 13818-1[3]. Constraints for transmitting AVC still pictures are defined in section 9.0 of this document.
6.3.2.2 Caption service descriptor When caption services are delivered within the AVC video elementary stream (as specified in Section 8.0), the caption_service_descriptor() , as defined in Sec. 6.9.2 of ATSC A/65C [2], shall be present as described in SCTE 54 [1] section 5.8.3.6.
6.3.2.3 SCTE Adaptation field data descriptor When private data bytes of the adaptation field of the TS packets are in use, with tag, length, and data structures as defined in Section 6.4.3, the SCTE_adaptation_field_data_descriptor shall be placed in the descriptor loop for the video program element of the PMT. In the absence of such adaptation field private data, the descriptor shall not be included in the corresponding ES_info_loop of the PMT. The presence of the SCTE_adaptation_field_descriptor() shall mean that private_data_byte(s) carried in adaptation field data in this stream are in tag-length-data format, where the tag values are as defined in SCTE standards. The absence of this descriptor does not preclude private data in the adaptation header that could conform to MPEG or other standards. The SCTE adaptation field data descriptor shall be formatted per Table 2.
Note: This descriptor varies from the signaling mechanism used by DVB[8] to indicate the presence of AU_Information. The descriptor establishes announcement for general and consistent syntax and semantics for the private data of the TS packet’s adaptation field.