Stream based bitrate transcoder for MPEG coded video
AssigneeSony Corporation
InventorHung-Ju Lee
Life of this patent
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Abstract
A stream based bitrate transcoder for MPEG bitstreams that utilizes information extracted from MPEG bitstreams, such as picture-type, coding complexity, motion vector and MB-mode. Using this information, a stream-based bitrate conversion of rhythm is realized. DCT coefficients are dropped with regard to two components, specifically, picture/MB-level classification and motion reference calculation.
Claims10
A method of video bitrate transcoding comprising:
- extracting information comprising motion vectors and picture/macroblock (MB) type for all frames in a GOP from a bitstream;
- calculating a number of bits for encoding discrete cosine transform (DCT) coefficients by VLC decoding and transforming the bitstream into a DCT bitstream;
- determining a bitrate difference;
- and
- dropping DCT coefficients based upon the information in order to achieve the bitrate difference in the DCT bitstream.
A method method in accordance with claim 6 wherein the bitrate difference is achieved by proportionally distributing DCT coefficients to be dropped among anchor frames, predicted frames and block frames.
A method in accordance with claim 7 wherein priority for proportionally distributing the DCT coefficients to be dropped is anchor frame<predicted frame<block frame.
Dependencies are inferred from the claim text.