Importance

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Abstract

Methods and apparatus for inserting data into an encoded data stream are disclosed. In accordance with the disclosed methods data is inserted into an encoded data stream while maintaining MPEG-2 compliance. The disclosed methods achieve data reduction required to make room for the data to be added by removing certain data elements of an encoded data stream, such as high frequency discrete cosine transform coefficients, which can be removed with minimal impact on picture quality and without disturbing the data stream's compliance with MPEG 2. In a first embodiment, data reduction to make room for the data to be inserted is performed by depacketizing the encoded data, performing a data reduction operation thereon, and then re-packetizing the encoded data. The reduced rate data stream is then multiplexed with the data to be inserted. In a second embodiment data reduction is performed by combining the contents of two or more consecutive transport data packets, e.g., the contents of a cluster of data packets, into a single data packet and by then inserting new data packets representing the data to be inserted, into the locations in the data stream corresponding to the original location of the transport data packets which were eliminated through the data reduction operation.

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First Claim