VIDEO SIGNAL TRANSMISSION

摘要

This invention relates to the generation of an MPEG video stream, which contains several slightly different programs, each with approximately the same content. The MPEG stream is constructed in such a manner that a simple transcoder can effectively select one of the programs. This is achieved by storing the differences relative to the default program in selected user data fields. The transcoder is little more than an MPEG bit stream parser, which replaces the bits corresponding to a selected set of macroblocks by the replacement data stored in the user data fields. A standard MPEG decoder without any knowledge of the embedded user data fields will simply extract the default program. One application of the invention relates to broadcasting of a television program with and without a logo, or a commercial with and without a public warning. Another application relates to copy-protection schemes. In such a scheme, the default program contains a ticket indicating that the contents may be copied once. Upon recording, this ticket is removed and replaced by the content accommodated in the user data field.