Subject: Re: IDCT algorithms

From: [email-masked] (Vasudev Bhaskara)
Date: Wed, 10 Aug 1994 23:52:54 GMT

Michael Simmons  - faculties ([email-masked]) wrote:
: I have been doing some reading up on IDCT algorithms
: Am I correct in saying that the algorithm presented in the paper,
: "A Forward-Mapping Realization of the Inverse Discrete Cosine Transform"
: by Leonard McMillan and Lee Westover of SUN,
: is the best for Microprocessor based MPEG decoding.

: I have read about 5 papers now and as far as I can tell they
: are all pretty similar.

: Is there any particular paper that any one could recommend to me.

:
  The McMillan-Westover method uses a cache (essentially a lookup table) and
  depending on your processor this may or may not be fast. In fact, for
  faster decoding, the paper "Statistical IDCT for Image Compression",
  Andy C. Hung and Teresa H.Y. Meng in SPIE, Vol.2187, Feb. 1994 shows the
  decoding speed (in kilo blocks/sec) for the Westover method versus others
  and depending on compression ratio and processor, the forward mapping 
  scheme was not that fast. for example, on the Lena image (for JPEG; the
  same should hold for MPEG data too), on a Sparc, faster methods yield a
  > 2X speedup over the forward mapping scheme and the same seems to hold
  for implementation on a MIPS machine. the faster scheme is an extension
  of the forward mapping approach wherein some symmetries are exploited in
  the IDCT kernel. 

   We have a faster scheme which gives realtime MPEG1 decompression on the
   HP workstations but the code is not in the public domain.

- Vasudev B.