mqc.c

This document is intended to serve as an introduction to Wavelet processing through a set of Matlab

/*
 * Copyright (c) 2001-2002, David Janssens
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS `AS IS'
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "mqc.h"

/* <summary> */
/* This struct defines the state of a context. */
/* </summary> */
typedef struct mqc_state_s {
    unsigned int qeval; /*  the probability of the Least Probable Symbol (0.75->0x8000, 1.5->0xffff) */
    int mps; /*  the Most Probable Symbol (0 or 1) */
    struct mqc_state_s *nmps; /*  next state if the next encoded symbol is the MPS */
    struct mqc_state_s *nlps; /*  next state if the next encoded symbol is the LPS */
} mqc_state_t;

/* <summary> */
/* This array defines all the possible states for a context. */
/* </summary> */
mqc_state_t mqc_states[47*2]={
    {0x5601, 0, &mqc_states[2], &mqc_states[3]},
    {0x5601, 1, &mqc_states[3], &mqc_states[2]},
    {0x3401, 0, &mqc_states[4], &mqc_states[12]},
    {0x3401, 1, &mqc_states[5], &mqc_states[13]},
    {0x1801, 0, &mqc_states[6], &mqc_states[18]},
    {0x1801, 1, &mqc_states[7], &mqc_states[19]},
    {0x0ac1, 0, &mqc_states[8], &mqc_states[24]},
    {0x0ac1, 1, &mqc_states[9], &mqc_states[25]},
    {0x0521, 0, &mqc_states[10], &mqc_states[58]},
    {0x0521, 1, &mqc_states[11], &mqc_states[59]},
    {0x0221, 0, &mqc_states[76], &mqc_states[66]},
    {0x0221, 1, &mqc_states[77], &mqc_states[67]},
    {0x5601, 0, &mqc_states[14], &mqc_states[13]},
    {0x5601, 1, &mqc_states[15], &mqc_states[12]},
    {0x5401, 0, &mqc_states[16], &mqc_states[28]},
    {0x5401, 1, &mqc_states[17], &mqc_states[29]},
    {0x4801, 0, &mqc_states[18], &mqc_states[28]},
    {0x4801, 1, &mqc_states[19], &mqc_states[29]},
    {0x3801, 0, &mqc_states[20], &mqc_states[28]},
    {0x3801, 1, &mqc_states[21], &mqc_states[29]},
    {0x3001, 0, &mqc_states[22], &mqc_states[34]},
    {0x3001, 1, &mqc_states[23], &mqc_states[35]},
    {0x2401, 0, &mqc_states[24], &mqc_states[36]},
    {0x2401, 1, &mqc_states[25], &mqc_states[37]},
    {0x1c01, 0, &mqc_states[26], &mqc_states[40]},
    {0x1c01, 1, &mqc_states[27], &mqc_states[41]},
    {0x1601, 0, &mqc_states[58], &mqc_states[42]},
    {0x1601, 1, &mqc_states[59], &mqc_states[43]},
    {0x5601, 0, &mqc_states[30], &mqc_states[29]},
    {0x5601, 1, &mqc_states[31], &mqc_states[28]},
    {0x5401, 0, &mqc_states[32], &mqc_states[28]},
    {0x5401, 1, &mqc_states[33], &mqc_states[29]},
    {0x5101, 0, &mqc_states[34], &mqc_states[30]},
    {0x5101, 1, &mqc_states[35], &mqc_states[31]},
    {0x4801, 0, &mqc_states[36], &mqc_states[32]},
    {0x4801, 1, &mqc_states[37], &mqc_states[33]},
    {0x3801, 0, &mqc_states[38], &mqc_states[34]},
    {0x3801, 1, &mqc_states[39], &mqc_states[35]},
    {0x3401, 0, &mqc_states[40], &mqc_states[36]},
    {0x3401, 1, &mqc_states[41], &mqc_states[37]},
    {0x3001, 0, &mqc_states[42], &mqc_states[38]},
    {0x3001, 1, &mqc_states[43], &mqc_states[39]},
    {0x2801, 0, &mqc_states[44], &mqc_states[38]},
    {0x2801, 1, &mqc_states[45], &mqc_states[39]},
    {0x2401, 0, &mqc_states[46], &mqc_states[40]},
    {0x2401, 1, &mqc_states[47], &mqc_states[41]},
    {0x2201, 0, &mqc_states[48], &mqc_states[42]},
    {0x2201, 1, &mqc_states[49], &mqc_states[43]},
    {0x1c01, 0, &mqc_states[50], &mqc_states[44]},
    {0x1c01, 1, &mqc_states[51], &mqc_states[45]},
    {0x1801, 0, &mqc_states[52], &mqc_states[46]},
    {0x1801, 1, &mqc_states[53], &mqc_states[47]},
    {0x1601, 0, &mqc_states[54], &mqc_states[48]},
    {0x1601, 1, &mqc_states[55], &mqc_states[49]},
    {0x1401, 0, &mqc_states[56], &mqc_states[50]},
    {0x1401, 1, &mqc_states[57], &mqc_states[51]},
    {0x1201, 0, &mqc_states[58], &mqc_states[52]},
    {0x1201, 1, &mqc_states[59], &mqc_states[53]},
    {0x1101, 0, &mqc_states[60], &mqc_states[54]},
    {0x1101, 1, &mqc_states[61], &mqc_states[55]},
    {0x0ac1, 0, &mqc_states[62], &mqc_states[56]},
    {0x0ac1, 1, &mqc_states[63], &mqc_states[57]},
    {0x09c1, 0, &mqc_states[64], &mqc_states[58]},
    {0x09c1, 1, &mqc_states[65], &mqc_states[59]},
    {0x08a1, 0, &mqc_states[66], &mqc_states[60]},
    {0x08a1, 1, &mqc_states[67], &mqc_states[61]},
    {0x0521, 0, &mqc_states[68], &mqc_states[62]},
    {0x0521, 1, &mqc_states[69], &mqc_states[63]},
    {0x0441, 0, &mqc_states[70], &mqc_states[64]},
    {0x0441, 1, &mqc_states[71], &mqc_states[65]},
    {0x02a1, 0, &mqc_states[72], &mqc_states[66]},
    {0x02a1, 1, &mqc_states[73], &mqc_states[67]},
    {0x0221, 0, &mqc_states[74], &mqc_states[68]},
    {0x0221, 1, &mqc_states[75], &mqc_states[69]},
    {0x0141, 0, &mqc_states[76], &mqc_states[70]},
    {0x0141, 1, &mqc_states[77], &mqc_states[71]},
    {0x0111, 0, &mqc_states[78], &mqc_states[72]},
    {0x0111, 1, &mqc_states[79], &mqc_states[73]},
    {0x0085, 0, &mqc_states[80], &mqc_states[74]},
    {0x0085, 1, &mqc_states[81], &mqc_states[75]},
    {0x0049, 0, &mqc_states[82], &mqc_states[76]},
    {0x0049, 1, &mqc_states[83], &mqc_states[77]},
    {0x0025, 0, &mqc_states[84], &mqc_states[78]},
    {0x0025, 1, &mqc_states[85], &mqc_states[79]},
    {0x0015, 0, &mqc_states[86], &mqc_states[80]},
    {0x0015, 1, &mqc_states[87], &mqc_states[81]},
    {0x0009, 0, &mqc_states[88], &mqc_states[82]},
    {0x0009, 1, &mqc_states[89], &mqc_states[83]},
    {0x0005, 0, &mqc_states[90], &mqc_states[84]},
    {0x0005, 1, &mqc_states[91], &mqc_states[85]},
    {0x0001, 0, &mqc_states[90], &mqc_states[86]},
    {0x0001, 1, &mqc_states[91], &mqc_states[87]},
    {0x5601, 0, &mqc_states[92], &mqc_states[92]},
    {0x5601, 1, &mqc_states[93], &mqc_states[93]},
};

#define MQC_NUMCTXS 32

unsigned int mqc_c;
unsigned int mqc_a;
unsigned int mqc_ct;
unsigned char *mqc_bp;
unsigned char *mqc_start;
unsigned char *mqc_end;
mqc_state_t *mqc_ctxs[MQC_NUMCTXS];
mqc_state_t **mqc_curctx;

/* <summary> */
/* Return the number of bytes already encoded. */
/* </summary> */
int mqc_numbytes() {
    return mqc_bp-mqc_start;
}

/* <summary> */
/* Output a byte, doing bit-stuffing if necessary. */
/* After a 0xff byte, the next byte must be smaller than 0x90 */
/* </summary> */
void mqc_byteout()
{
    if (*mqc_bp==0xff) {
        mqc_bp++;
        *mqc_bp=(unsigned char)(mqc_c>>20);             /*  cast should disable the conversion warning */
        mqc_c&=0xfffff;
        mqc_ct=7;
    } else {
        if ((mqc_c&0x8000000)==0) {
            mqc_bp++;
            *mqc_bp=(unsigned char)(mqc_c>>19);         /*  cast should disable the conversion warning */
            mqc_c&=0x7ffff;
            mqc_ct=8;
        } else {
            (*mqc_bp)++;
            if (*mqc_bp==0xff) {
                mqc_c&=0x7ffffff;
                mqc_bp++;
                *mqc_bp=(unsigned char)(mqc_c>>20);     /*  cast should disable the conversion warning */
                mqc_c&=0xfffff;
                mqc_ct=7;
            } else {
                mqc_bp++;
                *mqc_bp=(unsigned char)(mqc_c>>19);     /*  cast should disable the conversion warning */
                mqc_c&=0x7ffff;
                mqc_ct=8;
            }
        }
    }
}

/* <summary> */
/* Renormalize mqc_a and mqc_c while encoding, so that mqc_a stays between 0x8000 and 0x10000 */
/* </summary> */
void mqc_renorme()
{
    do {
        mqc_a<<=1;
        mqc_c<<=1;
        mqc_ct--;
        if (mqc_ct==0) {
            mqc_byteout();
        }
    } while ((mqc_a&0x8000)==0);
}

/* <summary> */
/* Encode the most probable symbol. */
/* </summary> */
void mqc_codemps()
{
    mqc_a-=(*mqc_curctx)->qeval;
    if ((mqc_a&0x8000)==0) {
        if (mqc_a<(*mqc_curctx)->qeval) {
            mqc_a=(*mqc_curctx)->qeval;
        } else {
            mqc_c+=(*mqc_curctx)->qeval;
        }
        *mqc_curctx=(*mqc_curctx)->nmps;
        mqc_renorme();
    } else {
        mqc_c+=(*mqc_curctx)->qeval;
    }
}

/* <summary> */
/* Encode the most least symbol. */
/* </summary> */
void mqc_codelps()
{
    mqc_a-=(*mqc_curctx)->qeval;
    if (mqc_a<(*mqc_curctx)->qeval) {
        mqc_c+=(*mqc_curctx)->qeval;
    } else {
        mqc_a=(*mqc_curctx)->qeval;
    }
    *mqc_curctx=(*mqc_curctx)->nlps;
    mqc_renorme();
}

/* <summary> */
/* Initialize encoder. */
/* </summary> */
/* <param name="bp">Output buffer.</param> */
void mqc_init_enc(unsigned char *bp)
{
    mqc_setcurctx(0);
    mqc_a=0x8000;
    mqc_c=0;
    mqc_bp=bp-1;
    mqc_ct=12;
    if (*mqc_bp==0xff) {
        mqc_ct=13;
    }
    mqc_start=bp;
}

/* <summary> */
/* Set current context. */
/* </summary> */
/* <param name="ctxno">Context number.</param> */
void mqc_setcurctx(int ctxno)
{
    mqc_curctx=&mqc_ctxs[ctxno];
}

/* <summary> */
/* Encode a symbol using the MQ-coder. */
/* </summary> */
/* <param name="d"> The symbol to be encoded (0 or 1).</param> */
void mqc_encode(int d)
{
    if ((*mqc_curctx)->mps==d) {
        mqc_codemps();
    } else {
        mqc_codelps();
    }
}

/* <summary> */
/* Fill mqc_c with 1s for flushing */
/* </summary> */
void mqc_setbits()
{
    unsigned int tempc=mqc_c+mqc_a;
    mqc_c|=0xffff;
    if (mqc_c>=tempc) {
        mqc_c-=0x8000;
    }
}

/* <summary> */
/* Flush encoded data. */
/* </summary> */
void mqc_flush()
{
    mqc_setbits();
    mqc_c<<=mqc_ct;
    mqc_byteout();
    mqc_c<<=mqc_ct;
    mqc_byteout();
    if (*mqc_bp!=0xff) {
        mqc_bp++;
    }
}

/* <summary> */
/* </summary> */
int mqc_mpsexchange()
{
    int d;
    if (mqc_a<(*mqc_curctx)->qeval) {
        d=1-(*mqc_curctx)->mps;
        *mqc_curctx=(*mqc_curctx)->nlps;
    } else {
        d=(*mqc_curctx)->mps;
        *mqc_curctx=(*mqc_curctx)->nmps;
    }
    return d;
}

/* <summary> */
/* </summary> */
int mqc_lpsexchange()
{
    int d;
    if (mqc_a<(*mqc_curctx)->qeval) {
        mqc_a=(*mqc_curctx)->qeval;
        d=(*mqc_curctx)->mps;
        *mqc_curctx=(*mqc_curctx)->nmps;
    } else {
        mqc_a=(*mqc_curctx)->qeval;
        d=1-(*mqc_curctx)->mps;
        *mqc_curctx=(*mqc_curctx)->nlps;
    }
    return d;
}

/* <summary> */
/* Input a byte. */
/* </summary> */
void mqc_bytein()
{
    if (mqc_bp!=mqc_end) {
        unsigned int c;
        if (mqc_bp+1!=mqc_end) {
            c=*(mqc_bp+1);
        } else {
            c=0xff;
        }
        if (*mqc_bp==0xff) {
            if (c>0x8f) {
                mqc_c+=0xff00;
                mqc_ct=8;
            } else {
                mqc_bp++;
                mqc_c+=c<<9;
                mqc_ct=7;
            }
        } else {
            mqc_bp++;
            mqc_c+=c<<8;
            mqc_ct=8;
        }
    } else {
        mqc_c+=0xff00;
        mqc_ct=8;
    }
}

/* <summary> */
/* Renormalize mqc_a and mqc_c while decoding. */
/* </summary> */
void mqc_renormd()
{
    do {
        if (mqc_ct==0) {
            mqc_bytein();
        }
        mqc_a<<=1;
        mqc_c<<=1;
        mqc_ct--;
    } while (mqc_a<0x8000);
}

/* <summary> */
/* Initialize decoder. */
/* </summary> */
void mqc_init_dec(unsigned char *bp, int len)
{
    mqc_setcurctx(0);
    mqc_start=bp;
    mqc_end=bp+len;
    mqc_bp=bp;
    mqc_c=*mqc_bp<<16;
    mqc_bytein();
    mqc_c<<=7;
    mqc_ct-=7;
    mqc_a=0x8000;
}

/* <summary> */
/* Decode a symbol. */
/* </summary> */
int mqc_decode()
{
    int d;
    mqc_a-=(*mqc_curctx)->qeval;
    if ((mqc_c>>16)<(*mqc_curctx)->qeval) {
        d=mqc_lpsexchange();
        mqc_renormd();
    } else {
        mqc_c-=(*mqc_curctx)->qeval<<16;
        if ((mqc_a&0x8000)==0) {
            d=mqc_mpsexchange();
            mqc_renormd();
        } else {
            d=(*mqc_curctx)->mps;
        }
    }
    return d;
}

/* <summary> */
/* Reset states of all contexts. */
/* </summary> */
void mqc_resetstates() {
    int i;
    for (i=0; i<MQC_NUMCTXS; i++) {
        mqc_ctxs[i]=mqc_states;
    }
}

/* <summary> */
/* Set the state for a context. */
/* </summary> */
/* <param name="ctxno">Context number</param> */
/* <param name="msb">Most significant bit</param> */
/* <param name="prob">Index to the probability of symbols</param> */
void mqc_setstate(int ctxno, int msb, int prob) {
    mqc_ctxs[ctxno]=&mqc_states[msb+(prob<<1)];
}