ANSI SCTE 128-2 pdf free download

ANSI SCTE 128-2 pdf free download.AVC Video Constraints for Cable Television Part 2- Transport.
6.4.2.2. SRAP Picture Decoding Time Stamp and SRAP Picture Presentation Time Stamp Constraints The AVC Bitstream shall contain necessary elements such that all pictures with PTS greater than or equal to DTSSRAP + 0.5 seconds (where DTSSRAP represents the decoding time stamp of an SRAP Picture) are fully reconstructable and displayable when decoding starts at the SRAP picture. Note 1: This implies that any picture that has a PTS >= [DTSSRAP + 0.5 seconds] cannot be predicted directly or indirectly from reference pictures that were transmitted prior to the SRAP (i.e., with a lower value of DTS than DTSSRAP). This also implies that any picture that was transmitted prior to the SRAP as well as any partially reconstructed pictures in the time interval [DTSSRAP, DTSSRAP + 0.5 seconds], cannot have a PTS that is greater than or equal to [DTSSRAP + 0.5 seconds]. The time difference between the receipt of an SRAP (actual value of PCR if present in the transport packet or computed value of PCR for the transport packet containing SRAP) and the DTS/PTS of its SRAP Picture is another key component in determining channel change time. The time difference between the receipt of an SRAP and the DTS of its SRAP Picture is also known as the initial video buffering delay of the AVC Bitstream in the CPB. Like in MPEG-2 video, the maximum possible initial video buffering delay is determined by the size of the CPB divided by the AVC Bitstream’s actual bitrate. The initial video buffering delay shall be limited to 3 seconds or less. For applications requiring fast channel change or small initial delay after random access, the initial video buffering delay should be limited to one second or less. Note 2: The maximum delay of data through the T-STD is 10 seconds for AVC while it was 1 second for MPEG-2 video, and the ratio of CPB buffer size to maximum bitrate is also higher for AVC. In order to improve the channel change time or reduce the initial delay after random access for AVC, transmission systems should use a reasonable data delay
6.4.2.3. Constraints on Decoding Time Stamps For applications where fast channel change or random access is important, the maximum time interval between the decoding time stamp of successive SRAP Pictures shall be less than or equal to 1 second for integer frame rates, with appropriate adjustment (less than two pictures) for (1) non-integer frame rates and (2) small variabilities associated with scene change detection during encoding. Note: The frequency at which SRAP access units are inserted into an AVC Bitstream is one of the key components in determining the channel change time and may simplify splicing and trick mode operations. If the interval between the Decoding Time Stamps of two successive SRAP Pictures is too small, such as 0.2 seconds, compression efficiency might be lowered significantly. On the other hand, if the interval between the Decoding Time Stamps of two successive SRAP Pictures is too large (such as 5 seconds), the time to effect a channel change or the initial delay after random access may be longer.
ANSI SCTE 128-2 pdf download.