Coded picture buffer arrival and nominal removal times in video coding

摘要

A video coding device, such as a video decoder, may be configured to derive at least one of a coded picture buffer (CPB) arrival time and a CPB nominal removal time for an access unit (AU) at both an access unit level and a sub-picture level regardless of a value of a syntax element that defines whether a decoding unit (DU) is the entire AU. The video coding device may further be configured to determine a removal time of the AU based at least in part on one of the CPB arrival time and a CPB nominal removal time and decode video data of the AU based at least in part on the removal time.

主权项

1. A method for decoding video data, the method comprising:
determining a value of a syntax element, the value of the syntax element signaling whether or not sub-picture level coded picture buffer (CPB) removal delay parameters are present in a picture timing Supplemental Enhancement Information (SEI) messages; regardless of a value of a variable, deriving a CPB arrival time for an access unit (AU) and a nominal removal time for the AU at an AU level, wherein a CPB operates at the AU level when the value of the variable is 0 and the CPB operates at a sub-picture level when the value of the variable is 1; setting a nominal removal time of a decoding unit (DU) based on the syntax element indicating whether the sub-picture level CPB removal delay parameters are present in the picture timing SEI messages, wherein based on the syntax element indicating the sub-picture level CPB removal delay parameters are not present in the picture timing SEI messages, the nominal removal time of the DU is set equal to the nominal removal time for the AU minus a sub-picture clock tick multiplied by a CPB removal delay, wherein based on the syntax element indicating the sub-picture level CPB removal delay parameters are present in the picture timing SEI messages, the nominal removal time of the DU is set equal to a nominal removal time of a next DU minus the sub-picture clock tick multiplied by the CPB removal delay; based on the variable being equal to 1 and either a low_delay_hrd_flag being equal to 0 or the nominal removal time of the DU being greater than or equal to a final CPB arrival time of the DU, setting a CPB removal time of the DU to the nominal removal time of the DU; and at the CPB removal time of the DU, decoding the DU.