STATISTICAL MULTIPLEXER AND REMULTIPLEXER THAT ACCOMMODATES CHANGES IN STRUCTURE OF GROUP OF PICTURES.

摘要

A system for rate control during transcoding and encoding of digital video data in a multi program transmission environment accommodates changes in the GOP structure of any of the programs, e.g., due to a commercial insertion or the like. A hierarchical bit allocation scheme is used, where bits are allocated on a super group of pictures (GOP) level (106), i.e., a grouping of multiple GOPs, a super frame level (104), and an individual frame level (102). The bit allocation for the super GOP and each picture is adjusted when a change in the structure of a group of pictures (GOP) is detected for any of the pre compressed programs. The super GOP length may also be adjusted if required to maintain an integer number of GOPs therein. A change in the GOP structure is detected based on a change in the GOP length or sub_GOP length (distance between P pictures). For pre compressed data, initial GOP lengths and sub_GOP lengths can be assumed and adjusted as required based on actual measurements. For a current I or P picture, the sub_GOP length is calculated based on temporal references of the current picture and a previous I or P picture. For a current B picture, the same calculation is used, plus one picture.