зеркало из https://github.com/mozilla/gecko-dev.git
118 строки
3.6 KiB
C
118 строки
3.6 KiB
C
/*
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* Copyright (c) 2017, Alliance for Open Media. All rights reserved
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*
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* This source code is subject to the terms of the BSD 2 Clause License and
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* the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
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* was not distributed with this source code in the LICENSE file, you can
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* obtain it at www.aomedia.org/license/software. If the Alliance for Open
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* Media Patent License 1.0 was not distributed with this source code in the
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* PATENTS file, you can obtain it at www.aomedia.org/license/patent.
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*/
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#include "aom_dsp/bitreader.h"
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#include "av1/common/common.h"
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// Inverse recenters a non-negative literal v around a reference r
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static uint16_t inv_recenter_nonneg(uint16_t r, uint16_t v) {
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if (v > (r << 1))
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return v;
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else if ((v & 1) == 0)
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return (v >> 1) + r;
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else
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return r - ((v + 1) >> 1);
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}
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// Inverse recenters a non-negative literal v in [0, n-1] around a
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// reference r also in [0, n-1]
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static uint16_t inv_recenter_finite_nonneg(uint16_t n, uint16_t r, uint16_t v) {
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if ((r << 1) <= n) {
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return inv_recenter_nonneg(r, v);
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} else {
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return n - 1 - inv_recenter_nonneg(n - 1 - r, v);
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}
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}
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int16_t aom_read_primitive_symmetric(aom_reader *r, unsigned int mag_bits) {
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if (aom_read_bit(r, NULL)) {
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int s = aom_read_bit(r, NULL);
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int16_t x = aom_read_literal(r, mag_bits, NULL) + 1;
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return (s > 0 ? -x : x);
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} else {
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return 0;
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}
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}
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uint16_t aom_read_primitive_quniform(aom_reader *r, uint16_t n) {
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if (n <= 1) return 0;
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const int l = get_msb(n - 1) + 1;
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const int m = (1 << l) - n;
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const int v = aom_read_literal(r, l - 1, NULL);
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return v < m ? v : (v << 1) - m + aom_read_bit(r, NULL);
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}
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uint16_t aom_read_primitive_refbilevel(aom_reader *r, uint16_t n, uint16_t p,
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uint16_t ref) {
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if (n <= 1) return 0;
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assert(p > 0 && p <= n);
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assert(ref < n);
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int lolimit = ref - p / 2;
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const int hilimit = lolimit + p - 1;
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if (lolimit < 0) {
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lolimit = 0;
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} else if (hilimit >= n) {
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lolimit = n - p;
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}
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int v;
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if (aom_read_bit(r, NULL)) {
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v = aom_read_primitive_quniform(r, p) + lolimit;
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} else {
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v = aom_read_primitive_quniform(r, n - p);
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if (v >= lolimit) v += p;
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}
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return v;
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}
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// Decode finite subexponential code that for a symbol v in [0, n-1] with
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// parameter k
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uint16_t aom_read_primitive_subexpfin(aom_reader *r, uint16_t n, uint16_t k) {
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int i = 0;
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int mk = 0;
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uint16_t v;
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while (1) {
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int b = (i ? k + i - 1 : k);
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int a = (1 << b);
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if (n <= mk + 3 * a) {
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v = aom_read_primitive_quniform(r, n - mk) + mk;
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break;
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} else {
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if (aom_read_bit(r, NULL)) {
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i = i + 1;
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mk += a;
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} else {
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v = aom_read_literal(r, b, NULL) + mk;
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break;
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}
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}
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}
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return v;
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}
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// Decode finite subexponential code that for a symbol v in [0, n-1] with
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// parameter k
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// based on a reference ref also in [0, n-1].
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uint16_t aom_read_primitive_refsubexpfin(aom_reader *r, uint16_t n, uint16_t k,
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uint16_t ref) {
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return inv_recenter_finite_nonneg(n, ref,
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aom_read_primitive_subexpfin(r, n, k));
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}
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// Decode finite subexponential code that for a symbol v in [-(n-1), n-1] with
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// parameter k based on a reference ref also in [-(n-1), n-1].
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int16_t aom_read_signed_primitive_refsubexpfin(aom_reader *r, uint16_t n,
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uint16_t k, int16_t ref) {
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ref += n - 1;
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const uint16_t scaled_n = (n << 1) - 1;
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return aom_read_primitive_refsubexpfin(r, scaled_n, k, ref) - n + 1;
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}
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