Method and system to replace sections of an encoded video bitstream

Abstract

A method and system in which a section of a previously encoded digital bit stream is replaced with another section of encoded video. In order to remove a section of encoded video, it is necessary to determine the beginning and ending points of the encoded video in the digitally encoded bit stream. The addresses of the beginning and ending points of the encoded data cannot be simply looked up but are calculated by summing the bits consumed by each picture, the number of bits of the sequence header of each picture, the number of bits of each Group of Pictures (GOP) header, and all stuff bits. In order to encode the video which is to be inserted in place of the removed video, a process is performed which prevents decoding artifacts from appearing. This is accomplished by determining the last P-picture before the edit point and using it as a reference frame for frames after the edit point. Additionally, a short period of the original video encoded using its original quantizer values is included at the end of the video to be substituted. Alternatively, the encoder may be run so that an earlier encoded reference picture is not used. However, this requires extra bits to maintain picture quality because initial bidirectional frames of the substitute video will use only one reference frame instead of two.