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/*
* Copyright (c) 2017, Alliance for Open Media. All rights reserved.
*
* This source code is subject to the terms of the BSD 2 Clause License and
* the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
* was not distributed with this source code in the LICENSE file, you can
* obtain it at www.aomedia.org/license/software. If the Alliance for Open
* Media Patent License 1.0 was not distributed with this source code in the
* PATENTS file, you can obtain it at www.aomedia.org/license/patent.
*/
#include "aom_dsp/bitwriter.h"
#include "aom_dsp/binary_codes_writer.h"
#include "aom_dsp/recenter.h"
#include "aom_ports/bitops.h"
// Encodes a value v in [0, n-1] quasi-uniformly
static void write_primitive_quniform(aom_writer *w, uint16_t n, uint16_t v) {
if (n <= 1) return;
const int l = get_msb(n) + 1;
const int m = (1 << l) - n;
if (v < m) {
aom_write_literal(w, v, l - 1);
} else {
aom_write_literal(w, m + ((v - m) >> 1), l - 1);
aom_write_bit(w, (v - m) & 1);
}
}
static int count_primitive_quniform(uint16_t n, uint16_t v) {
if (n <= 1) return 0;
const int l = get_msb(n) + 1;
const int m = (1 << l) - n;
return v < m ? l - 1 : l;
}
// Finite subexponential code that codes a symbol v in [0, n-1] with parameter k
static void write_primitive_subexpfin(aom_writer *w, uint16_t n, uint16_t k,
uint16_t v) {
int i = 0;
int mk = 0;
while (1) {
int b = (i ? k + i - 1 : k);
int a = (1 << b);
if (n <= mk + 3 * a) {
write_primitive_quniform(w, n - mk, v - mk);
break;
} else {
int t = (v >= mk + a);
aom_write_bit(w, t);
if (t) {
i = i + 1;
mk += a;
} else {
aom_write_literal(w, v - mk, b);
break;
}
}
}
}
static int count_primitive_subexpfin(uint16_t n, uint16_t k, uint16_t v) {
int count = 0;
int i = 0;
int mk = 0;
while (1) {
int b = (i ? k + i - 1 : k);
int a = (1 << b);
if (n <= mk + 3 * a) {
count += count_primitive_quniform(n - mk, v - mk);
break;
} else {
int t = (v >= mk + a);
count++;
if (t) {
i = i + 1;
mk += a;
} else {
count += b;
break;
}
}
}
return count;
}
// Finite subexponential code that codes a symbol v in [0, n-1] with parameter k
// based on a reference ref also in [0, n-1].
// Recenters symbol around r first and then uses a finite subexponential code.
void aom_write_primitive_refsubexpfin(aom_writer *w, uint16_t n, uint16_t k,
uint16_t ref, uint16_t v) {
write_primitive_subexpfin(w, n, k, recenter_finite_nonneg(n, ref, v));
}
int aom_count_primitive_refsubexpfin(uint16_t n, uint16_t k, uint16_t ref,
uint16_t v) {
return count_primitive_subexpfin(n, k, recenter_finite_nonneg(n, ref, v));
}
int aom_count_signed_primitive_refsubexpfin(uint16_t n, uint16_t k, int16_t ref,
int16_t v) {
ref += n - 1;
v += n - 1;
const uint16_t scaled_n = (n << 1) - 1;
return aom_count_primitive_refsubexpfin(scaled_n, k, ref, v);
}
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