1 /*
2 * Copyright (c) 2010 The WebM project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 #ifndef VP9_ENCODER_VP9_WRITER_H_
12 #define VP9_ENCODER_VP9_WRITER_H_
13
14 #include "vpx_ports/mem.h"
15
16 #include "vp9/common/vp9_prob.h"
17
18 #ifdef __cplusplus
19 extern "C" {
20 #endif
21
22 typedef struct {
23 unsigned int lowvalue;
24 unsigned int range;
25 unsigned int value;
26 int count;
27 unsigned int pos;
28 uint8_t *buffer;
29
30 // Variables used to track bit costs without outputing to the bitstream
31 unsigned int measure_cost;
32 uint64_t bit_counter;
33 } vp9_writer;
34
35 void vp9_start_encode(vp9_writer *bc, uint8_t *buffer);
36 void vp9_stop_encode(vp9_writer *bc);
37
vp9_write(vp9_writer * br,int bit,int probability)38 static void vp9_write(vp9_writer *br, int bit, int probability) {
39 unsigned int split;
40 int count = br->count;
41 unsigned int range = br->range;
42 unsigned int lowvalue = br->lowvalue;
43 register unsigned int shift;
44
45 split = 1 + (((range - 1) * probability) >> 8);
46
47 range = split;
48
49 if (bit) {
50 lowvalue += split;
51 range = br->range - split;
52 }
53
54 shift = vp9_norm[range];
55
56 range <<= shift;
57 count += shift;
58
59 if (count >= 0) {
60 int offset = shift - count;
61
62 if ((lowvalue << (offset - 1)) & 0x80000000) {
63 int x = br->pos - 1;
64
65 while (x >= 0 && br->buffer[x] == 0xff) {
66 br->buffer[x] = 0;
67 x--;
68 }
69
70 br->buffer[x] += 1;
71 }
72
73 br->buffer[br->pos++] = (lowvalue >> (24 - offset));
74 lowvalue <<= offset;
75 shift = count;
76 lowvalue &= 0xffffff;
77 count -= 8;
78 }
79
80 lowvalue <<= shift;
81 br->count = count;
82 br->lowvalue = lowvalue;
83 br->range = range;
84 }
85
vp9_write_bit(vp9_writer * w,int bit)86 static void vp9_write_bit(vp9_writer *w, int bit) {
87 vp9_write(w, bit, 128); // vp9_prob_half
88 }
89
vp9_write_literal(vp9_writer * w,int data,int bits)90 static void vp9_write_literal(vp9_writer *w, int data, int bits) {
91 int bit;
92
93 for (bit = bits - 1; bit >= 0; bit--)
94 vp9_write_bit(w, 1 & (data >> bit));
95 }
96
97 #define vp9_write_prob(w, v) vp9_write_literal((w), (v), 8)
98
99 #ifdef __cplusplus
100 } // extern "C"
101 #endif
102
103 #endif // VP9_ENCODER_VP9_WRITER_H_
104