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/*
* Copyright (c) 2016, 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.
*/
#ifndef AOM_DSP_ANSWRITER_H_
#define AOM_DSP_ANSWRITER_H_
// An implementation of Asymmetric Numeral Systems
// http://arxiv.org/abs/1311.2540v2
// Implements encoding of:
// * rABS (range Asymmetric Binary Systems), a boolean coder
// * rANS (range Asymmetric Numeral Systems), a multi-symbol coder
#include <assert.h>
#include "./aom_config.h"
#include "aom/aom_integer.h"
#include "aom_dsp/ans.h"
#include "aom_dsp/prob.h"
#include "aom_ports/mem_ops.h"
#include "av1/common/odintrin.h"
#if RANS_PRECISION <= OD_DIVU_DMAX
#define ANS_DIVREM(quotient, remainder, dividend, divisor) \
do { \
quotient = OD_DIVU_SMALL((dividend), (divisor)); \
remainder = (dividend) - (quotient) * (divisor); \
} while (0)
#else
#define ANS_DIVREM(quotient, remainder, dividend, divisor) \
do { \
quotient = (dividend) / (divisor); \
remainder = (dividend) % (divisor); \
} while (0)
#endif
#define ANS_DIV8(dividend, divisor) OD_DIVU_SMALL((dividend), (divisor))
#ifdef __cplusplus
extern "C" {
#endif // __cplusplus
struct AnsCoder {
uint8_t *buf;
int buf_offset;
uint32_t state;
};
static INLINE void ans_write_init(struct AnsCoder *const ans,
uint8_t *const buf) {
ans->buf = buf;
ans->buf_offset = 0;
ans->state = L_BASE;
}
static INLINE int ans_write_end(struct AnsCoder *const ans) {
uint32_t state;
int ans_size;
assert(ans->state >= L_BASE);
assert(ans->state < L_BASE * IO_BASE);
state = ans->state - L_BASE;
if (state < (1u << 15)) {
mem_put_le16(ans->buf + ans->buf_offset, (0x00u << 15) + state);
ans_size = ans->buf_offset + 2;
#if ANS_REVERSE
#if L_BASE * IO_BASE > (1 << 23)
} else if (state < (1u << 22)) {
mem_put_le24(ans->buf + ans->buf_offset, (0x02u << 22) + state);
ans_size = ans->buf_offset + 3;
} else if (state < (1u << 30)) {
mem_put_le32(ans->buf + ans->buf_offset, (0x03u << 30) + state);
ans_size = ans->buf_offset + 4;
#else
} else if (state < (1u << 23)) {
mem_put_le24(ans->buf + ans->buf_offset, (0x01u << 23) + state);
ans_size = ans->buf_offset + 3;
#endif
#else
} else if (state < (1u << 22)) {
mem_put_le24(ans->buf + ans->buf_offset, (0x02u << 22) + state);
ans_size = ans->buf_offset + 3;
} else if (state < (1u << 29)) {
mem_put_le32(ans->buf + ans->buf_offset, (0x07u << 29) + state);
ans_size = ans->buf_offset + 4;
#endif
} else {
assert(0 && "State is too large to be serialized");
return ans->buf_offset;
}
#if ANS_REVERSE
{
int i;
uint8_t tmp;
for (i = 0; i < (ans_size >> 1); i++) {
tmp = ans->buf[i];
ans->buf[i] = ans->buf[ans_size - 1 - i];
ans->buf[ans_size - 1 - i] = tmp;
}
ans->buf += ans_size;
ans->buf_offset = 0;
ans->state = L_BASE;
}
#endif
return ans_size;
}
// Write one boolean using rABS where p0 is the probability of the value being
// zero.
static INLINE void rabs_write(struct AnsCoder *ans, int value, AnsP8 p0) {
const AnsP8 p = ANS_P8_PRECISION - p0;
const unsigned l_s = value ? p : p0;
unsigned state = ans->state;
while (state >= L_BASE / ANS_P8_PRECISION * IO_BASE * l_s) {
ans->buf[ans->buf_offset++] = state % IO_BASE;
state /= IO_BASE;
}
const unsigned quotient = ANS_DIV8(state, l_s);
const unsigned remainder = state - quotient * l_s;
ans->state = quotient * ANS_P8_PRECISION + remainder + (value ? p0 : 0);
}
// Encode one symbol using rANS.
// cum_prob: The cumulative probability before this symbol (the offset of
// the symbol in the symbol cycle)
// prob: The probability of this symbol (l_s from the paper)
// RANS_PRECISION takes the place of m from the paper.
static INLINE void rans_write(struct AnsCoder *ans, aom_cdf_prob cum_prob,
aom_cdf_prob prob) {
unsigned quotient, remainder;
while (ans->state >= L_BASE / RANS_PRECISION * IO_BASE * prob) {
ans->buf[ans->buf_offset++] = ans->state % IO_BASE;
ans->state /= IO_BASE;
}
ANS_DIVREM(quotient, remainder, ans->state, prob);
ans->state = quotient * RANS_PRECISION + remainder + cum_prob;
}
#undef ANS_DIV8
#undef ANS_DIVREM
#ifdef __cplusplus
} // extern "C"
#endif // __cplusplus
#endif // AOM_DSP_ANSWRITER_H_
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