Differences between version dated 2001-02-19 20:11:09 and 2001-02-21 23:17:09
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Describe InverseDiscreteCosineTransform here.
iDCT algorithms are used in the decompression of mpeg2 and ac3 streams.
iDCT algorithms are used in the decompression of mpeg2 streams.
Some graphics adaptors, such as the ATI Rage128, are able to perform mpeg2 iDCT operations in hardware. Although the GatosProject has produced an Xv driver, the Xv architecture only supports scaling and colorspace transforms, and not motion compensation or iDCT.
A Discrete Cosine transorm decomposes a two dimensional waveform into its basis functions. MPEG-2 uses an 8x8 DCT, with 64 coefficients.
Some graphics adaptors, such as the ATI Rage128, are able to perform mpeg2 iDCT operations in hardware. Although the GatosProject has produced an Xv driver, the Xv architecture only supports scaling and colorspace transforms, and not [MotionCompensation] or iDCT. Documentation for an open source driver is difficult to obtain.
In the absence of dedicated hardware, the algorithm is sometimes implemented using 3DNow, MMX, or SSE instructions.
AC-3 uses a compression algorithm called the modified discrete cosine transform. The modified DCT uses 50% overlapping windows of 512 coeffients...
--JeremyErwin
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MoinMoin 1.108, Copyright © 2000-2001 by Jürgen Hermann
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