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
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
|
#include "RangeCoder.h"
void InitializePPMdRangeCoder(PPMdRangeCoder *self,
PPMdReadFunction *readfunc,void *inputcontext,
bool uselow,int bottom)
{
self->readfunc=readfunc;
self->inputcontext=inputcontext;
self->low=0;
self->code=0;
self->range=0xffffffff;
self->uselow=uselow;
self->bottom=bottom;
for(int i=0;i<4;i++) self->code=(self->code<<8)|readfunc(inputcontext);
}
uint32_t PPMdRangeCoderCurrentCount(PPMdRangeCoder *self,uint32_t scale)
{
self->range/=scale;
return (self->code-self->low)/self->range;
}
void RemovePPMdRangeCoderSubRange(PPMdRangeCoder *self,uint32_t lowcount,uint32_t highcount)
{
if(self->uselow) self->low+=self->range*lowcount;
else self->code-=self->range*lowcount;
self->range*=highcount-lowcount;
NormalizePPMdRangeCoder(self);
}
int NextWeightedBitFromPPMdRangeCoder(PPMdRangeCoder *self,int weight,int size)
{
uint32_t val=PPMdRangeCoderCurrentCount(self,size);
if(val<weight)
{
RemovePPMdRangeCoderSubRange(self,0,weight);
return 0;
}
else
{
RemovePPMdRangeCoderSubRange(self,weight,size);
return 1;
}
}
int NextWeightedBitFromPPMdRangeCoder2(PPMdRangeCoder *self,int weight,int shift)
{
uint32_t threshold=(self->range>>shift)*weight;
int bit;
if(self->code<threshold) // <= ?
{
bit=0;
self->range=threshold;
}
else
{
bit=1;
self->range-=threshold;
self->code-=threshold;
}
NormalizePPMdRangeCoder(self);
return bit;
}
void NormalizePPMdRangeCoder(PPMdRangeCoder *self)
{
for(;;)
{
if( (self->low^(self->low+self->range))>=0x1000000 )
{
if(self->range>=self->bottom) break;
else self->range=-self->low&(self->bottom-1);
}
int byte=self->readfunc(self->inputcontext);
self->code=(self->code<<8)|byte;
self->range<<=8;
self->low<<=8;
}
}
|
