libit

00001 /*
00002    libit - Library for basic source and channel coding functions
00003    Copyright (C) 2005-2005 Vivien Chappelier, Herve Jegou
00004 
00005    This library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Library General Public
00007    License as published by the Free Software Foundation; either
00008    version 2 of the License, or (at your option) any later version.
00009 
00010    This library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Library General Public License for more details.
00014 
00015    You should have received a copy of the GNU Library General Public
00016    License along with this library; if not, write to the Free
00017    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
00018 */
00019 
00020 /*
00021   Arithmetic coder/decoder
00022   Copyright (C) 2005 Vivien Chappelier
00023 */
00024 
00025 /*---------------------------------------------------------------------------*/
00026 /*! \defgroup entropycoding                                                  */
00027 /* @{                                                                        */
00028 /*---------------------------------------------------------------------------*/
00029 
00030 #ifndef __it_arithmetic_codec_h
00031 #define __it_arithmetic_codec_h
00032 
00033 typedef unsigned char arithmetic_codec_bit_t;
00034 typedef unsigned long arithmetic_codec_register_t;
00035 
00036 typedef struct _arithmetic_coder_t_ {
00037   int  precision;                       /* # bits of precision */
00038   arithmetic_codec_register_t lower;  /* lower bound of the interval */
00039   arithmetic_codec_register_t range;  /* range of the interval */
00040   int  pending;                         /* # pending bits to be written */
00041   bvec buffer;                          /* buffer for the sequence of bits */
00042   arithmetic_codec_bit_t *sequence; /* pointer to the current bit */
00043 } arithmetic_coder_t;
00044 
00045 typedef struct _arithmetic_decoder_t_ {
00046   int  precision;                       /* # bits of precision */
00047   arithmetic_codec_register_t lower;  /* lower bound of the interval */
00048   arithmetic_codec_register_t range;  /* range of the interval */
00049   arithmetic_codec_register_t value;  /* encoded value */
00050   bvec buffer;                          /* sequence of bits */
00051   arithmetic_codec_bit_t *sequence; /* pointer to the current bit */
00052 } arithmetic_decoder_t;
00053 
00054 
00055 /* encoder constructor/destructor */
00056 arithmetic_coder_t *arithmetic_coder_new (int precision);
00057 void arithmetic_coder_delete (arithmetic_coder_t * arithmetic_coder);
00058 
00059 /* start encoding */
00060 void arithmetic_coder_start (arithmetic_coder_t * arithmetic_coder,
00061            bvec buffer);
00062 /* stop encoding and return the number of bits written to the buffer */
00063 int  arithmetic_coder_stop (arithmetic_coder_t * arithmetic_coder);
00064 
00065 /* encode one bit with probability prob_0 of being 0 */
00066 void arithmetic_coder_encode_bit (arithmetic_coder_t * arithmetic_coder,
00067           double prob_0, arithmetic_codec_bit_t bit);
00068 /* encode a symbol with the binary arithmetic coder using unary binarization */
00069 void arithmetic_coder_encode_symbol (arithmetic_coder_t * arithmetic_coder,
00070              vec pdf, int symbol);
00071 
00072 /* decoder constructor/destructor */
00073 arithmetic_decoder_t *arithmetic_decoder_new (int precision);
00074 void arithmetic_decoder_delete (arithmetic_decoder_t * arithmetic_decoder);
00075 
00076 /* start decoding */
00077 void arithmetic_decoder_start (arithmetic_decoder_t * arithmetic_decoder,
00078              bvec buffer);
00079 /* stop decoding and return the number of bits read from the buffer */
00080 int  arithmetic_decoder_stop (arithmetic_decoder_t * arithmetic_decoder);
00081 
00082 /* decode one bit with probability prob_zero of being 0 */
00083 arithmetic_codec_bit_t arithmetic_decoder_decode_bit (arithmetic_decoder_t *
00084                   arithmetic_decoder,
00085                   double prob_zero);
00086 
00087 /* decode a symbol with the binary arithmetic coder using unary binarization */
00088 int  arithmetic_decoder_decode_symbol (arithmetic_decoder_t *
00089                arithmetic_decoder, vec pdf);
00090 
00091 /*@}*/
00092 
00093 #endif
include/it/arithmetic_codec.h
