releasenotes-spiht

该源码是SPIHT即分层树集合划分算法的c代码,希望对搞压缩编码的朋友们有用.

                             Q C C P A C K S P I H T

                            Version 0.34, 06-jul-2001

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Version 0.34:

  No changes.

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Version 0.33:

  No changes.

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Version 0.32:

  No changes.

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Version 0.31:

  Minor changes to permit support for multithreaded applications.

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Version 0.30:

  Mostly minor bug fixes.

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Version 0.29:

  There was a minor bug in the shape-adaptive capability added with the 
  last version. Specifically, in spihtencode, the specified bit rate was
  used with the size of the image to calculate the target number of bits
  for the coding. This is correct for entire-image coding; however, for
  shape-adaptive coding, the actual number of non-transparent pixels,
  rather than the size of the entire image, should be used in this
  calculation. This version corrects this problem.

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Version 0.28:

  The SPIHT coder has been made capable of shape-adaptive coding. That is,
  the SPIHT coder can now accept a transparency mask that indicates 
  arbitrarily shaped, non-transparent regions in the image that
  are to be coded. A shape-adaptive DWT (SA-DWT) is applied to these
  regions, and all transparent pixels are forever marked as insignificant
  coefficients. The SPIHT algorithm processes these "transparent coefficients"
  in a manner identical to that of other insignificant coefficients.
  Although not considered in the original SPIHT formulation by Said and
  Pearlman, SA-DWTs have been recently included in Version 2 of the
  MPEG-4 standard, wherein they are used for texture coding of
  arbitrarily shaped still objects. The marking of transparency as 
  perpetually insignificant coefficients, has been described for
  several zerotree-based coders as part of the MPEG-4 effort.

  In previous versions, several error messages normally accumulate in the
  QccError message queue due to the method used for stopping encoding when
  the allotted bit budget is exhausted; QccSPIHTEncode() ignores these
  messages and the corresponding error codes from low-level routines, but
  did not clear the messages from the error queue. Calls to
  QccErrorClearMessages() are now made before normal error-free return
  from QccSPIHTEncode() and QccSPIHTDecode() so that the error queue
  correctly reflects the error-free status of the coder.

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Version 0.27:

  Due to a change in the underlying QccBitBuffer routines in the QccPack
  main distribution, bitstreams produced by the QccPackSPIHT Version 0.27
  SPIHT coder will not be backward compatible with earlier version of
  QccPackSPIHT, *nor* will bitstreams produced by earlier QccPackSPIHT
  versions be readable by Version 0.27. For more information, refer to
  the RELEASE_NOTES file for the QccPack main distribution.

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Version 0.26:

  No changes.

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Version 0.25:

  Minor changes to reflect modified interfaces to
  QccENTArithmeticEncodeStart() and QccENTArithmeticDecodeStart().

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Version 0.24:

  The SPIHT coder has been modified extensively.  Support for arithmetic
  coding has been added.  Additionally, the performance of the
  "binary-uncoded" mode (i.e., encoding without arithmetic coding) has
  been improved and brought closer to the performance originally reported
  by Said and Pearlman.  An extensive quantitative comparison between
  the QccPackSPIHT coder and the original reported results now appears
  in the man page QccSPIHTEncode(3).  Bottom line: QccPackSPIHT is now
  typically only 0.15 dB below reported results in binary-uncoded and
  arithmetic-coded modes.

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Version 0.23:

  Minor build changes which should be transparent to users and developers.

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Version 0.22:

  Minor build changes which should be transparent to users and developers.

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Version 0.21:

  The only change made in this version is that the SPIHT code has been
  removed from the "main" QccPack distribution and placed in a separate,
  optional module that must be downloaded separately.  This change arose 
  from concerns that QccPack was not "purely" GPL/LGPL, in its entirety,
  due to the special non-GPL licensing accompanying the SPIHT code.
  With SPIHT now in the QccPackSPIHT module, the main QccPack distribution
  is now completely GPL/LGPL with the module being covered by the special
  SPIHT license as before.  We hope that the downloading a separate
  module-distribution file and the corresponding minor additional
  configuration step needed to build QccPack with SPIHT support will not
  unduly burden users of the QccPack SPIHT implementation.  We hope
  that other algorithms which may similarly require non-GPL licensing, or
  otherwise best be kept separated from the main QccPack distribution, may
  be accommodated as additional modules in the future.

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