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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 "av1/common/common.h"
// Recenters a non-negative literal v around a reference r
static uint16_t recenter_nonneg(uint16_t r, uint16_t v) {
if (v > (r << 1))
return v;
else if (v >= r)
return ((v - r) << 1);
else
return ((r - v) << 1) - 1;
}
// Recenters a non-negative literal v in [0, n-1] around a
// reference r also in [0, n-1]
static uint16_t recenter_finite_nonneg(uint16_t n, uint16_t r, uint16_t v) {
if ((r << 1) <= n) {
return recenter_nonneg(r, v);
} else {
return recenter_nonneg(n - 1 - r, n - 1 - v);
}
}
// Codes a symbol v in [-2^mag_bits, 2^mag_bits].
// mag_bits is number of bits for magnitude. The alphabet is of size
// 2 * 2^mag_bits + 1, symmetric around 0, where one bit is used to
// indicate 0 or non-zero, mag_bits bits are used to indicate magnitide
// and 1 more bit for the sign if non-zero.
void aom_write_primitive_symmetric(aom_writer *w, int16_t v,
unsigned int abs_bits) {
if (v == 0) {
aom_write_bit(w, 0);
} else {
const int x = abs(v);
const int s = v < 0;
aom_write_bit(w, 1);
aom_write_bit(w, s);
aom_write_literal(w, x - 1, abs_bits);
}
}
int aom_count_primitive_symmetric(int16_t v, unsigned int abs_bits) {
return (v == 0 ? 1 : abs_bits + 2);
}
// Encodes a value v in [0, n-1] quasi-uniformly
void aom_write_primitive_quniform(aom_writer *w, uint16_t n, uint16_t v) {
if (n <= 1) return;
const int l = get_msb(n - 1) + 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);
}
}
int aom_count_primitive_quniform(uint16_t n, uint16_t v) {
if (n <= 1) return 0;
const int l = get_msb(n - 1) + 1;
const int m = (1 << l) - n;
return v < m ? l - 1 : l;
}
// Encodes a value v in [0, n-1] based on a reference ref also in [0, n-1]
// The closest p values of v from ref are coded using a p-ary quasi-unoform
// short code while the remaining n-p values are coded with a longer code.
void aom_write_primitive_refbilevel(aom_writer *w, uint16_t n, uint16_t p,
uint16_t ref, uint16_t v) {
if (n <= 1) return;
assert(p > 0 && p <= n);
assert(ref < n);
int lolimit = ref - p / 2;
int hilimit = lolimit + p - 1;
if (lolimit < 0) {
lolimit = 0;
hilimit = p - 1;
} else if (hilimit >= n) {
hilimit = n - 1;
lolimit = n - p;
}
if (v >= lolimit && v <= hilimit) {
aom_write_bit(w, 1);
v = v - lolimit;
aom_write_primitive_quniform(w, p, v);
} else {
aom_write_bit(w, 0);
if (v > hilimit) v -= p;
aom_write_primitive_quniform(w, n - p, v);
}
}
int aom_count_primitive_refbilevel(uint16_t n, uint16_t p, uint16_t ref,
uint16_t v) {
if (n <= 1) return 0;
assert(p > 0 && p <= n);
assert(ref < n);
int lolimit = ref - p / 2;
int hilimit = lolimit + p - 1;
if (lolimit < 0) {
lolimit = 0;
hilimit = p - 1;
} else if (hilimit >= n) {
hilimit = n - 1;
lolimit = n - p;
}
int count = 0;
if (v >= lolimit && v <= hilimit) {
count++;
v = v - lolimit;
count += aom_count_primitive_quniform(p, v);
} else {
count++;
if (v > hilimit) v -= p;
count += aom_count_primitive_quniform(n - p, v);
}
return count;
}
// Finite subexponential code that codes a symbol v in [0, n-1] with parameter k
void aom_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) {
aom_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;
}
}
}
}
int aom_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 += aom_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,
int16_t ref, int16_t v) {
aom_write_primitive_subexpfin(w, n, k, recenter_finite_nonneg(n, ref, v));
}
void aom_write_signed_primitive_refsubexpfin(aom_writer *w, uint16_t n,
uint16_t k, uint16_t ref,
uint16_t v) {
ref += n - 1;
v += n - 1;
const uint16_t scaled_n = (n << 1) - 1;
aom_write_primitive_refsubexpfin(w, scaled_n, k, ref, v);
}
int aom_count_primitive_refsubexpfin(uint16_t n, uint16_t k, uint16_t ref,
uint16_t v) {
return aom_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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