aom_dsp/entcode.h

/*
 * Copyright (c) 2001-2016, 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.
 */

#if !defined(_entcode_H)
#define _entcode_H (1)
#include <limits.h>
#include <stddef.h>
#include "av1/common/odintrin.h"

/*OPT: od_ec_window must be at least 32 bits, but if you have fast arithmetic
   on a larger type, you can speed up the decoder by using it here.*/
typedef uint32_t od_ec_window;

#define OD_EC_WINDOW_SIZE ((int)sizeof(od_ec_window) * CHAR_BIT)

/*The number of bits to use for the range-coded part of unsigned integers.*/
#define OD_EC_UINT_BITS (4)

/*The resolution of fractional-precision bit usage measurements, i.e.,
   3 => 1/8th bits.*/
#define OD_BITRES (3)

/*The value stored in an iCDF is 32768 minus the actual Q15 cumulative
   probability (an "inverse" CDF).
  This function converts from one representation to the other (and is its own
   inverse).*/
#define OD_ICDF(x) (32768U - (x))

/*See entcode.c for further documentation.*/

OD_WARN_UNUSED_RESULT uint32_t od_ec_tell_frac(uint32_t nbits_total,
                                               uint32_t rng);

#endif