changes_from_vm4_0.txt

JPEG2000实现的源码

                         CHANGES IN VM4.1 FROM VM4.0
	                 ===========================
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                                  Bug Fixes
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* Missing _increment_symbol_count macro call in mqenc() and mqdec() as part 
  of EBCOT_COUNT_SYMBOLS conditional compilation.
* Failed assertion during -red decoding for files with encoded ROI's.
* Incorrect arithmetic context when -Ccausal and -Ccolscan were used together 
  with the optional coder.
* Incorrect saves of MQ-coder information at end of check_segment_marker() 
  -Csegment error resilience routine.
* Various bugs with the Ricoh bitstream syntax.

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                             Compilation Problems/Warnings
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* Compilation warnings too numerous to identify were addressed.  Several 
  minor warnings still remain, but only with -Wall type compilation.
* Failed compilation with definition of EBCOT_COUNT_SYMBOLS.  

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                               Frames Processing
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* Two extra arguments were added to the -Fframes encoder option to help 
  facilitate a simpler implementation of BBDWT.  See discussion below and 
  encoder usage for further details on -Fframes.
* A -Cno_frames encoder flag was added and passed through the bitstream to 
  make the decoder ignore frames.  This allows SSWT and BBDWT to be used 
  without forcing the coder to conform to the same block paradigm.

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                                 Transforms
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* The block-based wavelet transform (BBDWT) with one sample overlap is now 
  invoked with the -Fframes encoder command line option.  To invoke this 
  transform, use "-Fframes H W 0 0 L L" on the encoder command line, where H 
  and W are the desired block sizes in the image domain and L is the number 
  of wavelet levels for which one-sample overlap should be used for both 
  horizontal and vertical directions.  Note that wavelet levels beyond L 
  will use full overlap wavelet processing.  See the -Fframes section of usage 
  for more details.  Also, please note that this transform method is only 
  available for lifting implementations of wavelet transforms.

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                                Entropy Coders
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* Several modifications were made to the optional entropy coder to reduce its 
  run time in both the encoder and decoder.  
* Parallel decoding with the optional coder is now feasible using the -Cmark 
  encoder command line option.  This is accomplished by inserting auxiliary 
  information indicating the relevant bit-stream length segments.
* Minor changes to the overall encoding scheme were made to help implement 
  the above changes.

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                              Arithmetic Coder
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* The arithmetic coder function get_minimum_bits() was replaced with the 
  function get_minimum_bytes().  This new function computes more efficient 
  termination points for the arithmetic coder, thus reducing the length of the 
  encoded bitstream for Ebcot.
  
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                               Error Resilience
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* With the error resilience bug fix stated above, the Sarnoff error resilience 
  feature invoked with the -Csegment encoder command line option is working 
  for Ebcot.  Changes were also made to add this error resilience feature to 
  the optional entropy coder.

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                             Bit-Stream Syntax
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* Many changes were made to the Ricoh syntax from VM4.0, including support 
  for remaining pieces of VM functionality, removing various bugs, and 
  addressing various compilation warnings.  As a result, this syntax is now 
  the only syntax available for VM4.1.

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                              Visual C++ Updates
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* The files related to this compiler should now be up to date.