| /* |
| * 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" |
| |
| // 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; |
| 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; |
| 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 |
| 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, |
| uint16_t ref, uint16_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, int16_t ref, |
| int16_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); |
| } |