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
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
|
// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef MEDIA_GPU_HRD_BUFFER_H_
#define MEDIA_GPU_HRD_BUFFER_H_
#include <stdint.h>
#include "base/time/time.h"
#include "media/gpu/media_gpu_export.h"
namespace media {
// Model of Hypothetical Reference Decoder (HRD) Buffer
// It's a model of a leaky bucket, where the data flows out of the buffer at a
// constant bitrate, while the data is filled in after every encoded frame. The
// encoding loop should call HRD Buffer methods in the following order:
// ...
// Shrink(timestamp); <- optional
// ...
// AddFrameBytes(frame_bytes, frame_timestamp);
// ...
class MEDIA_GPU_EXPORT HRDBuffer {
public:
// A basic constructor. Buffer size and bitrate are specified while the
// internal buffer state is set to default values. `buffer_size` is in bytes,
// `avg_bitrate` is in bits per second.
HRDBuffer(size_t buffer_size, uint32_t avg_bitrate);
// A constructor where the initial internal buffer state is specified: the
// size of the buffer and the timestamp when the last frame was added. It is
// suitable to be used when an encoding layer is added or removed in SVC case.
HRDBuffer(size_t buffer_size,
uint32_t avg_bitrate,
int last_frame_buffer_bytes,
base::TimeDelta last_frame_timestamp);
~HRDBuffer();
HRDBuffer(const HRDBuffer& other) = delete;
HRDBuffer& operator=(const HRDBuffer& other) = delete;
size_t buffer_size() const { return buffer_size_; }
uint32_t average_bitrate() const { return avg_bitrate_; }
// Indicates whether the buffer was overridden when the latest frame bytes
// were added to the buffer.
bool frame_overshooting() const { return frame_overshooting_; }
// Number of bytes in the buffer after the last encoded frame has been added.
int last_frame_buffer_bytes() const { return last_frame_buffer_bytes_; }
// The timestamp of the last added frame.
base::TimeDelta last_frame_timestamp() const { return last_frame_timestamp_; }
// The buffer fullness at the provided time. It is non-negative and equals
// zero in the case of buffer undershoot.
int GetBytesAtTime(base::TimeDelta timestamp) const;
// Space left in the buffer at the provided time. It is non-negative and
// equals zero in the case of buffer undershoot.
int GetBytesRemainingAtTime(base::TimeDelta timestamp) const;
// Sets the HRD buffer main parameters: buffer size and output data
// bitrate. `peak_bitrate` and `ease_hrd_reduction` parameters are used
// in smooth size transition, when the buffer size is reduced.
void SetParameters(size_t buffer_size,
uint32_t avg_bitrate,
uint32_t peak_bitrate,
bool ease_hrd_reduction);
// The method shrinks the buffer size gradually until it reaches the
// previously set buffer size. This method could be called in every encoding
// cycle.
void Shrink(base::TimeDelta timestamp);
// Adds encoded bytes to the buffer.
void AddFrameBytes(size_t frame_bytes, base::TimeDelta frame_timestamp);
private:
// Buffer size in bytes after the last frame has been added.
int last_frame_buffer_bytes_ = 0;
// Timestamp of the last added frame.
base::TimeDelta last_frame_timestamp_ = base::Microseconds(-1);
// Current HRD buffer size in bytes.
size_t buffer_size_ = 0;
// New HRD buffer size in bytes - when the buffer size changes.
size_t new_buffer_size_ = 0;
// Stream bitrate used in HRD model.
uint32_t avg_bitrate_ = 0;
// Frame overshooting indicator.
bool frame_overshooting_ = false;
// Shrinking duration of HRD buffer to a new, smaller size.
base::TimeDelta shrinking_bucket_wait_time_ = base::Microseconds(0);
// Delta rate used in the buffer size change.
int buffer_size_delta_rate_ = 0;
};
} // namespace media
#endif // MEDIA_GPU_HRD_BUFFER_H_
|
