qccentarithmeticencode.3

spiht for linux this is used to decod and encode vedio i wich all enjoy

                             SECOND_BLOCK_LENGTH,
                             model,
                             &output_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticEncode()",
                         argv[0]);
      QccErrorExit();
    }
  
  if (QccENTArithmeticEncodeEnd(model,
                                SECOND_CONTEXT,
                                &output_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticEncodeEnd()");
      QccErrorExit();
    }
  
  if (QccBitBufferEnd(&output_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccBitBufferEnd()",
                         argv[0]);
      QccErrorExit();
    }
  
  QccENTArithmeticFreeModel(model);
  
  QccExit;
}

.fi
.RE
.sp
.sp
.sp
Decoder:
.RS
.nf

/*  DECODER  */

#include "QccPack.h"

#define FIRST_CONTEXT 0
#define SECOND_CONTEXT 1

main(int argc, char *argv[])
{
  int symbol_stream[SYMBOL_STREAM_LENGTH];
  QccBitBuffer input_buffer;
  QccENTArithmeticModel *model = NULL;
  
  int num_contexts = 2;
  int num_symbols[2];

  QccInit(argc, argv);
  QccBitBufferInitialize(&input_buffer);
  
  for (context = 0; context < 2; context++)
    num_symbols[context] = NUM_SYMBOLS;
      
  input_buffer.type = QCCBITBUFFER_INPUT;
  if (QccBitBufferStart(&input_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccBitBufferStart()",
                         argv[0]);
      QccErrorExit();
    }
  
  if ((model = QccENTArithmeticDecodeStart(&input_buffer,
                                           num_symbols,
                                           2,
                                           NULL,
                                           QCCENT_ANYNUMBITS)) == NULL)
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticDecodeStart()",
                         argv[0]);
      QccErrorExit();
    }
  
  if (QccENTArithmeticSetModelContext(model, FIRST_CONTEXT))
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticSetModelContext()",
                         argv[0]);
      QccErrorExit();
    }

  if (QccENTArithmeticDecode(&input_buffer,
                             model,
                             symbol_stream, 
                             FIRST_BLOCK_LENGTH))
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticDecode()",
                         argv[0]);
      QccErrorExit();
    }
  
  if (QccENTArithmeticSetModelContext(model, SECOND_CONTEXT))
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticSetModelContext()",
                         argv[0]);
      QccErrorExit();
    }

  if (QccENTArithmeticDecode(&input_buffer,
                             model,
                             &symbol_stream[FIRST_BLOCK_LENGTH], 
                             SECOND_BLOCK_LENGTH))
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticDecode()",
                         argv[0]);
      QccErrorExit();
    }
  
  if (QccBitBufferEnd(&input_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccBitBufferEnd()",
                         argv[0]);
      QccErrorExit();
    }
  
  QccENTArithmeticFreeModel(model);
  
  /*  output symbols stream here  */

  QccExit;
}

.fi
.RE
.SS "Multiple-Context Adaptive Arithmetic Coding"
Multiple-context adaptive arithmetic coding in which the previous symbol
is used as the context of the current symbol. This coder would
be a reasonable choice for a Markov process. Note that the number
of contexts is equal to the number of symbols.
.br
.sp
Encoder:
.RS
.nf

/*  ENCODER  */

#include "QccPack.h"

int get_current_context(const int *symbol_stream,
                        int current_symbol)
{
  if ((symbol_stream == NULL) || (current_symbol <= 0))
    return(0);

  return(symbol_stream[current_symbol - 1]);
}


main(int argc, char *argv[])
{
  int symbol_stream[SYMBOL_STREAM_LENGTH];
  QccBitBuffer output_buffer;
  QccENTArithmeticModel *model = NULL;
  
  int num_contexts = NUM_SYMBOLS;
  int num_symbols[NUM_SYMBOLS];
  
  QccInit(argc, argv);
  QccBitBufferInitialize(&output_buffer);
  
  for (context = 0; context < NUM_SYMBOLS; context++)
    num_symbols[context] = NUM_SYMBOLS;
      
  /*  obtain symbols here */
  
  output_buffer.type = QCCBITBUFFER_OUTPUT;
  if (QccBitBufferStart(&output_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccBitBufferStart()",
                         argv[0]);
      QccErrorExit();
    }
  
  if ((model = QccENTArithmeticEncodeStart(num_symbols,
                                           num_contexts,
                                           get_current_context,
                                           QCCENT_ANYNUMBITS)) == NULL)
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticEncodeStart()",
                         argv[0]);
      QccErrorExit();
    }
  
  if (QccENTArithmeticEncode(symbol_stream, 
                             SYMBOL_STREAM_LENGTH,
                             model,
                             &output_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticEncode()",
                         argv[0]);
      QccErrorExit();
    }
  
  if (QccENTArithmeticEncodeEnd(model,
                                0,
                                &output_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticEncodeEnd()");
      QccErrorExit();
    }
  
  if (QccBitBufferEnd(&output_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccBitBufferEnd()",
                         argv[0]);
      QccErrorExit();
    }
  
  QccENTArithmeticFreeModel(model);
  
  QccExit;
}

.fi
.RE
.sp
.sp
.sp
Decoder:
.RS
.nf

/*  DECODER  */

#include "QccPack.h"

int get_current_context(const int *symbol_stream,
                        int current_symbol)
{
  if ((symbol_stream == NULL) || (current_symbol <= 0))
    return(0);

  return(symbol_stream[current_symbol - 1]);
}


main(int argc, char *argv[])
{
  int symbol_stream[SYMBOL_STREAM_LENGTH];
  QccBitBuffer input_buffer;
  QccENTArithmeticModel *model = NULL;

  int num_contexts = NUM_SYMBOLS;
  int num_symbols[NUM_SYMBOLS];
  
  QccInit(argc, argv);
  QccBitBufferInitialize(&input_buffer);
  
  for (context = 0; context < NUM_SYMBOLS; context++)
    num_symbols[context] = NUM_SYMBOLS;
      
  input_buffer.type = QCCBITBUFFER_INPUT;
  if (QccBitBufferStart(&input_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccBitBufferStart()",
                         argv[0]);
      QccErrorExit();
    }
  
  if ((model = QccENTArithmeticDecodeStart(&input_buffer,
                                           num_symbols,
                                           num_contexts,
                                           get_current_context,
                                           QCCENT_ANYNUMBITS)) == NULL)
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticDecodeStart()",
                         argv[0]);
      QccErrorExit();
    }
  
  if (QccENTArithmeticDecode(&input_buffer,
                             model,
                             symbol_stream, 
                             SYMBOL_STREAM_LENGTH))
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticDecode()",
                         argv[0]);
      QccErrorExit();
    }
  
  if (QccBitBufferEnd(&input_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccBitBufferEnd()",
                         argv[0]);
      QccErrorExit();
    }
  
  QccENTArithmeticFreeModel(model);
  
  /*  output symbols stream here  */

  QccExit;
}

.fi
.RE
.SS "Single-Context Nonadaptive Arithmetic Coding"
Straightforward single-context nonadaptive encoding.
Note that adaptive coding is used by default, so we merely need
to disable adaption before coding begins.
.br
.sp
Encoder:
.RS
.nf

/*  ENCODER  */

#include "QccPack.h"

main(int argc, char *argv[])
{
  int symbol_stream[SYMBOL_STREAM_LENGTH];
  QccBitBuffer output_buffer;
  QccENTArithmeticModel *model = NULL;
  double probabilities[NUM_SYMBOLS];
  
  QccInit(argc, argv);
  QccBitBufferInitialize(&output_buffer);
  
  /*  obtain symbols and their probabilities somehow here */
  
  output_buffer.type = QCCBITBUFFER_OUTPUT;
  if (QccBitBufferStart(&output_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccBitBufferStart()",
                         argv[0]);
      QccErrorExit();
    }
  
  if ((model = QccENTArithmeticEncodeStart(&NUM_SYMBOLS,
                                           1,
                                           NULL,
                                           QCCENT_ANYNUMBITS)) == NULL)
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticEncodeStart()",
                         argv[0]);
      QccErrorExit();
    }
  
  QccENTArithmeticSetModelAdaption(model, QCCENT_NONADAPTIVE);
  if (QccENTArithmeticSetModelProbabilities(model,
                                            probabilities,
                                            0))
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticSetModelProbabilities()",
                         argv[0]);
      QccErrorExit();
    }
  
  if (QccENTArithmeticEncode(symbol_stream, 
                             SYMBOL_STREAM_LENGTH,
                             model,
                             &output_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticEncode()",
                         argv[0]);
      QccErrorExit();
    }
  
  if (QccENTArithmeticEncodeEnd(model,
                                0,
                                &output_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticEncodeEnd()");
      QccErrorExit();
    }
  
  if (QccBitBufferEnd(&output_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccBitBufferEnd()",
                         argv[0]);
      QccErrorExit();
    }
  
  QccENTArithmeticFreeModel(model);
  
  QccExit;
}

.fi
.RE
.sp
.sp
.sp
Decoder:
.RS
.nf

/*  DECODER  */

#include "QccPack.h"

main(int argc, char *argv[])
{
  int symbol_stream[SYMBOL_STREAM_LENGTH];
  QccBitBuffer input_buffer;
  QccENTArithmeticModel *model = NULL;
  double probabilities[NUM_SYMBOLS];
  
  QccInit(argc, argv);
  QccBitBufferInitialize(&input_buffer);
  
  /*  obtain symbol probabilities somehow here */

  input_buffer.type = QCCBITBUFFER_INPUT;
  if (QccBitBufferStart(&input_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccBitBufferStart()",
                         argv[0]);
      QccErrorExit();
    }
  
  if ((model = QccENTArithmeticDecodeStart(&input_buffer,
                                           &NUM_SYMBOLS,
                                           1,
                                           NULL,
                                           QCCENT_ANYNUMBITS)) == NULL)
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticDecodeStart()",
                         argv[0]);
      QccErrorExit();
    }
  
  QccENTArithmeticSetModelAdaption(model, QCCENT_NONADAPTIVE);
  if (QccENTArithmeticSetModelProbabilities(model,
                                            probabilities,
                                            0))
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticSetModelProbabilities()",
                         argv[0]);
      QccErrorExit();
    }

  if (QccENTArithmeticDecode(&input_buffer,
                             model,
                             symbol_stream, 
                             SYMBOL_STREAM_LENGTH))
    {
      QccErrorAddMessage("%s: Error calling QccENTArithmeticDecode()",
                         argv[0]);
      QccErrorExit();
    }
  
  if (QccBitBufferEnd(&input_buffer))
    {
      QccErrorAddMessage("%s: Error calling QccBitBufferEnd()",
                         argv[0]);
      QccErrorExit();
    }
  
  QccENTArithmeticFreeModel(model);
  
  /*  output symbols stream here  */

  QccExit;
}

.fi
.RE
.SH "NOTES"
If
.BR QccENTArithmetocEncodeStart()
is called using
.I target_num_bits
equal to other than
.B QCCENT_ANYNUMBITS
in order to output exactly 
.I target_num_bits
(in which case,
.BR QccENTArithmeticEncodeEnd()
is usually
.I not
called at the end of the bitstream),
then the last few symbols decoded by
.BR QccENTArithmeticDecode()
as it nears the end of the bitstream will be valid
symbols, but may not be exactly the same as the last few symbols
passed to
.BR QccENTArithmeticEncode() .
This discrepancy
is due to the fact that the arithmetic
encoder probably had not completely flushed its state to the
bitstream when the
.I target_num_bits
threshold was reached.
Thus, the decoder may decode a few symbols
erroneously before it realizes that it has encountered
the end of the bitstream, since the decoder
needs the complete encoder state
(which is unknown because it was not flushed to
the bitstream) to decode accurately.
Usually, this is not a problem in applications since the
.I target_num_bits
capability is most likely only of use in lossy compression, and
the erroneously decoded symbols at the end of the
bitstream can be viewed as contributing negligible additional distortion
to the lossy representation.
.SH "SEE ALSO"
.BR QccENTArithmeticModel (3),
.BR QccENTArithmeticGetContext (3),
.BR QccBitBuffer (3),
.BR QccPackENT (3),
.BR QccPack (3)
.LP
I. H. Witten, R. M. Neal, and J. G. Cleary,
"Arithmetic Coding for Data Compression,"
.IR "Communications of the ACM" ,
vol. 30, no. 6, pp. 520-540, June 1987.
.SH AUTHOR
Copyright (C) 1997-2009  James E. Fowler
.\"  The programs herein are free software; you can redistribute them an.or
.\"  modify them under the terms of the GNU General Public License
.\"  as published by the Free Software Foundation; either version 2
.\"  of the License, or (at your option) any later version.
.\"  
.\"  These programs are distributed in the hope that they will be useful,
.\"  but WITHOUT ANY WARRANTY; without even the implied warranty of
.\"  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\"  GNU General Public License for more details.
.\"  
.\"  You should have received a copy of the GNU General Public License
.\"  along with these programs; if not, write to the Free Software
.\"  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.