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/*
* nd.c: Input 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 20:50:13 $
* $Author: hafner $
* $Revision: 5.1 $
* $State: Exp $
*/
#include "config.h"
#include "types.h"
#include "macros.h"
#include "error.h"
#include "bit-io.h"
#include "arith.h"
#include "misc.h"
#include "list.h"
#include "wfalib.h"
#include "nd.h"
/*****************************************************************************
prototypes
*****************************************************************************/
static void
decode_nd_coefficients (unsigned total, wfa_t *wfa, bitfile_t *input);
static unsigned
decode_nd_tree (wfa_t *wfa, bitfile_t *input);
/*****************************************************************************
public code
*****************************************************************************/
void
read_nd (wfa_t *wfa, bitfile_t *input)
/*
* Read transitions of the nondetermistic 'wfa' part from 'input' stream.
* ND is used only at levels {'wfa->p_min_level', ... , 'wfa->p_max_level'}.
*
* Side effects:
* 'wfa->into' and 'wfa->weights' are filled with the decoded values
*/
{
unsigned total = decode_nd_tree (wfa, input);
if (total > 0)
decode_nd_coefficients (total, wfa, input);
}
/*****************************************************************************
private code
*****************************************************************************/
static unsigned
decode_nd_tree (wfa_t *wfa, bitfile_t *input)
/*
* Read 'wfa' prediction tree of given 'input' stream.
*
* No return value.
*
* Side effects:
* 'wfa->into' is filled with the decoded values
*/
{
lqueue_t *queue; /* queue of states */
int next, state; /* state and its current child */
unsigned total = 0; /* total number of predicted states */
u_word_t sum0, sum1; /* Probability model */
u_word_t code; /* The present input code value */
u_word_t low; /* Start of the current code range */
u_word_t high; /* End of the current code range */
/*
* Initialize arithmetic decoder
*/
code = get_bits (input, 16);
low = 0;
high = 0xffff;
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 count; /* Current interval count */
unsigned range; /* Current interval range */
count = (((code - low) + 1) * sum1 - 1) / ((high - low) + 1);
if (count < sum0)
{
/*
* Decode a '0' symbol
* First, the range is expanded to account for the
* symbol removal.
*/
range = (high - low) + 1;
high = low + (u_word_t) ((range * sum0) / sum1 - 1 );
RESCALE_INPUT_INTERVAL;
/*
* Update the frequency counts
*/
sum0++;
sum1++;
if (sum1 > 50) /* scale the symbol frequencies */
{
sum0 >>= 1;
sum1 >>= 1;
if (!sum0)
sum0 = 1;
if (sum0 >= sum1)
sum1 = sum0 + 1;
}
if (wfa->level_of_state [state] > wfa->wfainfo->p_min_level)
queue_append (queue, &state);
}
else
{
/*
* Decode a '1' symbol
* First, the range is expanded to account for the
* symbol removal.
*/
range = (high - low) + 1;
high = low + (u_word_t) ((range * sum1) / sum1 - 1);
low = low + (u_word_t) ((range * sum0) / sum1);
RESCALE_INPUT_INTERVAL;
/*
* 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;
}
append_edge (next, 0, -1, label, wfa);
total++;
}
}
}
}
free_queue (queue);
INPUT_BYTE_ALIGN (input);
return total;
}
static void
decode_nd_coefficients (unsigned total, wfa_t *wfa, bitfile_t *input)
/*
* Read #'total' weights of nondeterministic part of 'wfa'
* of given 'input' stream.
* 'frame' gives the current frame number.
*
* No return value.
*
* Side effects:
* 'wfa->weights' is filled with the decoded values.
*/
{
unsigned *coefficients; /* array of factors to encode */
unsigned *ptr; /* pointer to current factor */
/*
* Decode array of coefficients stored with arithmetic coding
*/
{
const int scaling = 50; /* scaling factor of prob. model */
unsigned c_symbols = 1 << (wfa->wfainfo->dc_rpf->mantissa_bits + 1);
ptr = coefficients = decode_array (input, NULL, &c_symbols, 1,
total, scaling);
}
/*
* Fill 'wfa->weights' with decoded coefficients
*/
{
unsigned state, label;
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]))
{
wfa->weight [state][label][0] = btor (*ptr++,
wfa->wfainfo->dc_rpf);
wfa->int_weight [state][label][0]
= wfa->weight [state][label][0] * 512 + 0.5;
}
}
Free (coefficients);
}
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