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/*
* tree.c: Output of bintree partitioning
*
* Written by: Ullrich Hafner
*
* This file is part of FIASCO (Fractal Image And Sequence COdec)
* Copyright (C) 1994-2000 Ullrich Hafner
*/
/*
* $Date: 2000/06/14 20:50:31 $
* $Author: hafner $
* $Revision: 5.1 $
* $State: Exp $
*/
#include "config.h"
#include "types.h"
#include "macros.h"
#include "error.h"
#include "wfa.h"
#include "bit-io.h"
#include "arith.h"
#include "misc.h"
#include "tree.h"
/*****************************************************************************
prototypes
*****************************************************************************/
static void
encode_tree (bitfile_t *output, const byte_t *data, unsigned n_data,
unsigned scaling, u_word_t sum0, u_word_t sum1);
/*****************************************************************************
public code
*****************************************************************************/
void
write_tree (const wfa_t *wfa, bitfile_t *output)
/*
* Write bintree to stream 'output'.
* Traverse tree in breadth first order and save a '1' for each child
* and a '0' for each range image.
*
* No return value.
*/
{
unsigned queue [MAXSTATES]; /* state numbers in BFO */
unsigned current; /* current node to process */
unsigned last; /* last node (update every new node) */
unsigned label; /* current label */
int into; /* next child */
byte_t *tree_string; /* bitstring to encode */
unsigned total = 0; /* number of ranges */
unsigned bits = bits_processed (output); /* number of bits */
/*
* Traverse tree in breadth first order. Use a queue to store
* the children of each node ('last' is the next free queue element).
* The first element ('current') of this queue will get the new parent
* node.
*/
tree_string = Calloc (MAXSTATES * MAXLABELS, sizeof (byte_t));
queue [0] = wfa->root_state;
for (last = 1, current = 0; current < last; current++)
for (label = 0; label < MAXLABELS; label++)
if (!isrange (into = wfa->tree [queue[current]][label])) /* child ? */
{
queue [last++] = into;
tree_string [total++] = 1;
}
else /* or range ? */
tree_string [total++] = 0;
if (total != (wfa->states - wfa->basis_states) * MAXLABELS)
error ("total [%d] != (states - basis_states) * 2 [%d]", total,
(wfa->states - wfa->basis_states) * MAXLABELS);
{
unsigned scale = total / 20 ;
encode_tree (output, tree_string, total, scale, 1, 11);
}
Free (tree_string);
debug_message ("tree: %5d bits. (%5d symbols => %5.2f bps)",
bits_processed (output) - bits, total,
total > 0 ? ((bits_processed (output) - bits)
/ (double) total) : 0);
}
/*****************************************************************************
private code
*****************************************************************************/
static void
encode_tree (bitfile_t *output, const byte_t *data, unsigned n_data,
unsigned scaling, u_word_t sum0, u_word_t sum1)
/*
* Encode bintree data with adaptive binary arithmetic coding.
* Write 'n_data' output symbols stored in 'data' to stream 'output'.
* Rescale probability model after every 'scaling' symbols.
* Initial counts are given by 'sum0' and 'sum1'.
*
* No return value.
*/
{
u_word_t low; /* Start of the current code range */
u_word_t high; /* End of the current code range */
u_word_t underflow; /* Number of underflow bits pending */
unsigned n; /* Data counter */
low = 0;
high = 0xffff;
underflow = 0;
for (n = n_data; n; n--)
{
unsigned range; /* Current interval range */
if (!*data++)
{
/*
* encode a '0'
*/
range = (high - low) + 1;
high = low + (u_word_t) ((range * sum0) / sum1 - 1);
RESCALE_OUTPUT_INTERVAL;
sum0++;
}
else
{
/*
* encode a '1'
*/
range = (high - low) + 1;
low = low + (u_word_t) ((range * sum0) / sum1);
RESCALE_OUTPUT_INTERVAL;
}
/*
* Update the frequency counts
*/
sum1++;
if (sum1 > scaling) /* Scale the symbol frequencies */
{
sum0 >>= 1;
sum1 >>= 1;
if (!sum0)
sum0 = 1;
if (sum0 >= sum1)
sum1 = sum0 + 1;
}
}
/*
* Flush the quasi-arithmetic encoder
*/
low = high;
RESCALE_OUTPUT_INTERVAL;
OUTPUT_BYTE_ALIGN (output);
}
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