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 videodata in a multi-program transmissionenvironment accommodates changes in the GOP structure of any of the programs,e.g., due to a commercial insertion or the like. Ahierarchical bit allocation scheme is used, where bits are allocated on asuper group of pictures (GOP) level (106), i.e., a grouping ofmultiple GOPs, a super frame level (104), and an individual frame level (102).The bit allocation for the super GOP and each pictureis adjusted when a change in the structure of a group of pictures (GOP) isdetected for any of the pre-compressed programs. Thesuper GOP length may also be adjusted if required to maintain an integernumber of GOPs therein. A change in the GOP structureis detected based on a change in the GOP length or sub_GOP length (distancebetween P pictures). For pre-compressed data, initialGOP lengths and su_bGOP lengths can be assumed and adjusted as required basedon actual measurements. For a current I or Ppicture, the sub_GOP length is calculated based on temporal references of thecurrent picture and a previous I or P picture. For acurrent B picture, the same calculation is used, plus one picture.