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/*
* nd.c: Output of prediction tree
*
* 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 "arith.h"
#include "misc.h"
#include "bit-io.h"
#include "rpf.h"
#include "list.h"
#include "nd.h"
/*****************************************************************************
prototypes
*****************************************************************************/
static unsigned
encode_nd_tree (const wfa_t *wfa, bitfile_t *output);
static void
encode_nd_coefficients (unsigned total, const wfa_t *wfa, bitfile_t *output);
/*****************************************************************************
public code
*****************************************************************************/
void
write_nd (const wfa_t *wfa, bitfile_t *output)
/*
* Write prediction information of 'wfa' to given stream 'output'.
* Coefficients are quantized with model 'p_rpf'.
*
* No return value.
*/
{
unsigned total = encode_nd_tree (wfa, output);
if (total > 0)
encode_nd_coefficients (total, wfa, output);
}
/*****************************************************************************
private code
*****************************************************************************/
static unsigned
encode_nd_tree (const wfa_t *wfa, bitfile_t *output)
/*
* Write prediction tree of 'wfa' to given stream 'output'.
*
* No return value.
*/
{
lqueue_t *queue; /* queue of states */
int state, next; /* state and its current child */
unsigned used, not_used; /* counter ND used/not used */
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 */
u_word_t sum0, sum1; /* Probability model */
unsigned bits = bits_processed (output);
used = not_used = 0;
/*
* Initialize arithmetic coder
*/
low = 0;
high = 0xffff;
underflow = 0;
sum0 = 1;
sum1 = 11;
queue = alloc_queue (sizeof (int));
state = wfa->root_state;
queue_append (queue, &state);
/*
* Traverse the WFA tree in breadth first order (using a queue).
*/
while (queue_remove (queue, &next))
{
unsigned label;
if (wfa->level_of_state [next] > wfa->wfainfo->p_max_level + 1)
{
/*
* Nondetermismn is not allowed at levels larger than
* 'wfa->wfainfo->p_max_level'.
*/
for (label = 0; label < MAXLABELS; label++)
if (ischild (state = wfa->tree [next][label]))
queue_append (queue, &state); /* continue with children */
}
else if (wfa->level_of_state [next] > wfa->wfainfo->p_min_level)
{
for (label = 0; label < MAXLABELS; label++)
if (ischild (state = wfa->tree [next][label]))
{
unsigned range; /* Current interval range */
if (isedge (wfa->into [next][label][0])) /* prediction used */
{
used++;
/*
* Encode a '1' symbol
*/
range = (high - low) + 1;
low = low + (u_word_t) ((range * sum0) / sum1);
RESCALE_OUTPUT_INTERVAL;
}
else /* no predict., continue with children */
{
not_used++;
if (wfa->level_of_state [state] > wfa->wfainfo->p_min_level)
queue_append (queue, &state);
/*
* Encode a '0' symbol
*/
range = (high - low) + 1;
high = low + (u_word_t) ((range * sum0) / sum1 - 1);
RESCALE_OUTPUT_INTERVAL;
sum0++;
}
/*
* Update the frequency counts
*/
sum1++;
if (sum1 > 50) /* Scale the symbol frequencies */
{
sum0 >>= 1;
sum1 >>= 1;
if (!sum0)
sum0 = 1;
if (sum0 >= sum1)
sum1 = sum0 + 1;
}
}
}
}
free_queue (queue);
/*
* Flush the quasi-arithmetic encoder
*/
low = high;
RESCALE_OUTPUT_INTERVAL;
OUTPUT_BYTE_ALIGN (output);
debug_message ("%d nd fields: %d used nd, %d used not nd", used + not_used,
used, not_used);
{
unsigned total = used + not_used;
debug_message ("nd-tree: %5d bits. (%5d symbols => %5.2f bps)",
bits_processed (output) - bits, total,
total > 0 ? ((bits_processed (output) - bits) /
(double) total) : 0);
}
return used;
}
static void
encode_nd_coefficients (unsigned total, const wfa_t *wfa, bitfile_t *output)
/*
* Write #'total' weights of nondeterministic part of 'wfa' to given 'output'
* stream. Coefficients are stored with arithmetic coding (the model is
* given by 'p_rpf').
*
* No return value.
*/
{
unsigned bits = bits_processed (output);
{
unsigned *coefficients; /* array of factors to encode */
unsigned *ptr; /* pointer to current factor */
unsigned state, label, edge;
word_t domain;
ptr = coefficients = Calloc (total, sizeof (unsigned));
for (state = wfa->basis_states; state < wfa->states; state++)
for (label = 0; label < MAXLABELS; label++)
if (ischild (wfa->tree [state][label])
&& isedge (wfa->into [state][label][0]))
for (edge = 0; isedge (domain = wfa->into [state][label][edge]);
edge++)
{
if (ptr - coefficients >= (int) total)
error ("Can't write more than %d coefficients.", total);
*ptr++ = rtob (wfa->weight [state][label][edge],
wfa->wfainfo->dc_rpf);
}
/*
* Encode array of coefficients with arithmetic coding
*/
{
const int scaling = 50; /* scaling factor of prob. model */
unsigned c_symbols = 1 << (wfa->wfainfo->dc_rpf->mantissa_bits + 1);
encode_array (output, coefficients, NULL, &c_symbols, 1,
total, scaling);
}
debug_message ("nd-factors: %5d bits. (%5d symbols => %5.2f bps)",
bits_processed (output) - bits, total,
total ? ((bits_processed (output) - bits)
/ (double) total) : 0);
Free (coefficients);
}
}
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