diff options
Diffstat (limited to 'media/libaom/src/aom_dsp/binary_codes_writer.c')
| -rw-r--r-- | media/libaom/src/aom_dsp/binary_codes_writer.c | 210 |
1 files changed, 210 insertions, 0 deletions
diff --git a/media/libaom/src/aom_dsp/binary_codes_writer.c b/media/libaom/src/aom_dsp/binary_codes_writer.c new file mode 100644 index 0000000000..ee7a9f567e --- /dev/null +++ b/media/libaom/src/aom_dsp/binary_codes_writer.c @@ -0,0 +1,210 @@ +/* + * 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 "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; + 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 void aom_wb_write_primitive_quniform(struct aom_write_bit_buffer *wb, + 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_wb_write_literal(wb, v, l - 1); + } else { + aom_wb_write_literal(wb, m + ((v - m) >> 1), l - 1); + aom_wb_write_bit(wb, (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; + } + } + } +} + +static void aom_wb_write_primitive_subexpfin(struct aom_write_bit_buffer *wb, + 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_wb_write_primitive_quniform(wb, n - mk, v - mk); + break; + } else { + int t = (v >= mk + a); + aom_wb_write_bit(wb, t); + if (t) { + i = i + 1; + mk += a; + } else { + aom_wb_write_literal(wb, 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)); +} + +static void aom_wb_write_primitive_refsubexpfin(struct aom_write_bit_buffer *wb, + uint16_t n, uint16_t k, + uint16_t ref, uint16_t v) { + aom_wb_write_primitive_subexpfin(wb, 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); +} + +void aom_wb_write_signed_primitive_refsubexpfin(struct aom_write_bit_buffer *wb, + 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_wb_write_primitive_refsubexpfin(wb, 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); +} |