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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 #ifndef MEDIA_BASE_DOWNLOAD_RATE_MONITOR_H_ | |
6 #define MEDIA_BASE_DOWNLOAD_RATE_MONITOR_H_ | |
7 | |
8 #include <deque> | |
9 | |
10 #include "base/bind.h" | |
11 #include "base/callback.h" | |
12 #include "base/time.h" | |
13 #include "media/base/media_export.h" | |
14 | |
15 namespace media { | |
16 | |
17 // Measures download speed based on the rate at which a media file is buffering. | |
18 // Signals when it believes the media file can be played back without needing to | |
19 // pause to buffer. | |
20 class MEDIA_EXPORT DownloadRateMonitor { | |
21 public: | |
22 explicit DownloadRateMonitor(); | |
scherkus (not reviewing)
2011/11/16 02:15:17
nit: explicit isn't needed
| |
23 | |
24 // Begin measuring download rate. The monitor will run |canplaythrough_cb| | |
25 // when it believes the media can be played back without needing to pause to | |
26 // buffer. |media_bitrate| is the bitrate of the video. | |
27 void Start(const base::Closure& canplaythrough_cb, int media_bitrate); | |
28 | |
29 // Notifies the monitor of the current number of bytes buffered by the media | |
30 // file at what timestamp. The monitor expects subsequent calls to | |
31 // SetBufferedBytes to have monotonically nondecreasing timestamps. | |
32 // Calls to the method are ignored if monitor has not been started or is | |
33 // stopped. | |
34 void SetBufferedBytes(int64 buffered_bytes, const base::Time& timestamp); | |
35 | |
36 // Notifies the monitor when the media file has paused or continued | |
37 // downloading data. | |
38 void SetNetworkActivity(bool is_downloading_data); | |
39 | |
40 // Sets the size of the media file in bytes. | |
41 void SetTotalBytes(int64 total_bytes) { total_bytes_ = total_bytes; } | |
scherkus (not reviewing)
2011/11/16 02:15:17
trivial setters/getters should be unix_hacker() st
| |
42 | |
43 // Sets whether the media file is a fully loaded source. | |
44 void SetLoaded(bool loaded) { loaded_ = loaded; } | |
scherkus (not reviewing)
2011/11/16 02:15:17
set_loaded()
| |
45 | |
46 // Stop monitoring download rate. This does not discard previously learned | |
47 // information, but it will no longer factor incoming information into its | |
48 // canplaythrough estimation. | |
49 void Stop(); | |
50 | |
51 // Resets monitor to uninitialized state. | |
52 void Reset(); | |
53 | |
54 private: | |
55 // Represents a point in time in which the media was buffering data. | |
56 struct BufferingPoint { | |
57 // The number of bytes buffered by the media player at |timestamp|. | |
58 int64 buffered_bytes; | |
59 // Time at which buffering measurement was taken. | |
60 base::Time timestamp; | |
61 }; | |
62 | |
63 // Represents a span of time in which the media was buffering data. | |
64 class Sample { | |
65 public: | |
66 explicit Sample(); | |
scherkus (not reviewing)
2011/11/16 02:15:17
no explicit
| |
67 Sample(const BufferingPoint& start, const BufferingPoint& end); | |
68 | |
69 // Set the end point of the data sample. | |
70 void set_end(const BufferingPoint& new_end); | |
71 | |
72 const BufferingPoint& start() const { return start_; } | |
73 const BufferingPoint& end() const { return end_; } | |
74 | |
75 // Returns the bytes downloaded per second in this sample. Returns -1.0 if | |
76 // sample is invalid. | |
77 float bytes_per_second() const; | |
78 | |
79 // Returns the seconds elapsed in this sample. Returns -1.0 if the sample | |
80 // has not begun yet. | |
81 float seconds_elapsed() const; | |
82 | |
83 // Returns bytes downloaded in this sample. Returns -1.0 if the sample has | |
84 // not begun yet. | |
85 int64 bytes_downloaded() const; | |
86 | |
87 // Returns true if Sample has not been initialized. | |
88 bool is_null() const; | |
89 | |
90 // Resets the sample to an uninitialized state. | |
91 void Reset(); | |
92 | |
93 // Restarts the sample to begin its measurement at what was previously its | |
94 // end point. | |
95 void RestartAtEndBufferingPoint(); | |
96 | |
97 private: | |
98 BufferingPoint start_; | |
99 BufferingPoint end_; | |
100 }; | |
101 | |
102 int64 bytes_downloaded_in_window() const; | |
103 float seconds_elapsed_in_window() const; | |
104 | |
105 // Updates window with latest sample if it is ready. | |
106 void UpdateSampleWindow(); | |
107 | |
108 // Returns an approximation of the current download rate in bytes per second. | |
109 // Returns -1.0 if unknown. | |
110 float ApproximateDownloadByteRate() const; | |
111 | |
112 // Helper method that returns true if the monitor believes it should fire the | |
113 // |canplaythrough_cb_|. | |
114 bool ShouldNotifyCanPlayThrough(); | |
115 | |
116 // Examines the download rate and fires the |canplaythrough_cb_| callback if | |
117 // the monitor deems it the right time. | |
118 void NotifyCanPlayThroughIfNeeded(); | |
119 | |
120 // Callback to run when the monitor believes the media can play through | |
121 // without needing to pause to buffer. | |
122 base::Closure canplaythrough_cb_; | |
123 | |
124 // Indicates whether the monitor has run the |canplaythrough_cb_|. | |
125 bool has_notified_can_play_through_; | |
126 | |
127 // Measurements used to approximate download speed. | |
128 Sample current_sample_; | |
129 std::deque<Sample> sample_window_; | |
130 | |
131 // True if actively downloading bytes, false otherwise. | |
132 bool is_downloading_data_; | |
133 | |
134 // Total number of bytes in the media file, 0 if unknown or undefined. | |
135 int64 total_bytes_; | |
136 | |
137 // Amount of bytes buffered. | |
138 int64 buffered_bytes_; | |
139 | |
140 // True if the media file is a fully loaded source, e.g. file:// protocol. | |
141 bool loaded_; | |
142 | |
143 // Bitrate of the media file, 0 if unknown. | |
144 int bitrate_; | |
145 | |
146 // True if the monitor has not yet started or has been stopped, false | |
147 // otherwise. | |
148 bool stopped_; | |
149 | |
150 DISALLOW_COPY_AND_ASSIGN(DownloadRateMonitor); | |
151 }; | |
152 | |
153 } // namespace media | |
154 | |
155 #endif // MEDIA_BASE_DOWNLOAD_RATE_MONITOR_H_ | |
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