Image analysis – Image compression or coding – Transform coding
Patent
1997-12-31
2000-10-31
Couso, Jose L.
Image analysis
Image compression or coding
Transform coding
382277, 382299, 382233, G06K 936, G06K 946, G06K 932
Patent
active
061414565
ABSTRACT:
Methods and apparatus for combining linear image post-processing operations with an inverse discrete cosine transform (IDCT) operation are described. In accordance with various embodiments of the present invention IDCT and downsampling operations are combined into a single operation to achieve the same image processing result as sequential IDCT and downsampling operations. By combining the two operations and performing downsampling in the DCT, as opposed to pixel domain, significant complexity reduction is achieved over embodiments where the two operations are performed sequentially. In one particular embodiment, when interlaced images are being processed, combined IDCT/downsampling circuits which perform field based, as opposed to frame based, downsampling in the DCT domain are employed. The method and apparatus of the present invention can be used to implement circuits which perform a combined full order IDCT/downsampling operation and/or a reduced complexity combined full order IDCT/downsampling operation. The combined IDCT/downsampling methods and apparatus of the present invention are capable of supporting a wide range of downsampling ratios using, at least in some cases, fewer math operators, than are required to implement zonal filtering followed by a reduced order IDCT operation which requires the use of a contiguous subblock of DCT coefficients.
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Pearlstein Larry
Sazzad Sharif M.
Cage Shawn B.
Couso Jose L.
Hitachi America Ltd.
Straub Michael P.
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