blob: faacbd5b940817ca26fa1a33bca19b033f51d97a (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
|
// Copyright 2016 The Draco Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// File provides shared functions for adaptive rANS bit coding.
#ifndef DRACO_COMPRESSION_BIT_CODERS_ADAPTIVE_RANS_BIT_CODING_SHARED_H_
#define DRACO_COMPRESSION_BIT_CODERS_ADAPTIVE_RANS_BIT_CODING_SHARED_H_
#include "draco/core/macros.h"
namespace draco {
// Clamp the probability p to a uint8_t in the range [1,255].
inline uint8_t clamp_probability(double p) {
DRACO_DCHECK_LE(p, 1.0);
DRACO_DCHECK_LE(0.0, p);
uint32_t p_int = static_cast<uint32_t>((p * 256) + 0.5);
p_int -= (p_int == 256);
p_int += (p_int == 0);
return static_cast<uint8_t>(p_int);
}
// Update the probability according to new incoming bit.
inline double update_probability(double old_p, bool bit) {
static constexpr double w = 128.0;
static constexpr double w0 = (w - 1.0) / w;
static constexpr double w1 = 1.0 / w;
return old_p * w0 + (!bit) * w1;
}
} // namespace draco
#endif // DRACO_COMPRESSION_BIT_CODERS_ADAPTIVE_RANS_BIT_CODING_SHARED_H_
|
