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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 typedef base::Callback<void()> CanPlayThroughCB; | |
acolwell GONE FROM CHROMIUM
2011/11/15 21:43:10
nit: Consider just using base::Closure. I don't th
vrk (LEFT CHROMIUM)
2011/11/15 22:41:35
Done.
| |
23 | |
24 DownloadRateMonitor(); | |
25 | |
26 // Begin measuring download rate. The monitor will run |canplaythrough_cb| | |
27 // when it believes the media can be played back without needing to pause to | |
28 // buffer. |media_bitrate| is the bitrate of the video. | |
29 void Start(const CanPlayThroughCB& canplaythrough_cb, int media_bitrate); | |
30 | |
31 // Notifies the monitor of the current number of bytes buffered by the media | |
32 // file at what timestamp. The monitor expects subsequent calls to | |
33 // SetBufferedBytes to have monotonically nondecreasing timestamps. | |
34 // Calls to the method are ignored if monitor has not been started or is | |
35 // stopped. | |
36 void SetBufferedBytes(int64 buffered_bytes, const base::Time& timestamp); | |
37 | |
38 // Notifies the monitor when the media file has paused or continued | |
39 // downloading data. | |
40 void SetNetworkActivity(bool is_downloading_data); | |
41 | |
42 // Sets the size of the media file in bytes. | |
43 void SetTotalBytes(int64 total_bytes) { total_bytes_ = total_bytes; } | |
44 | |
45 // Sets whether the media file is a fully loaded source. | |
46 void SetLoaded(bool loaded) { loaded_ = loaded; } | |
47 | |
48 // Stop monitoring download rate. This does not discard previously learned | |
49 // information, but it will no longer factor incoming information into its | |
50 // canplaythrough estimation. | |
51 void Stop(); | |
52 | |
53 // Resets monitor to uninitialized state. | |
54 void Reset(); | |
55 | |
56 private: | |
57 // Represents a point in time in which the media was buffering data. | |
58 struct BufferingPoint { | |
59 // The number of bytes buffered by the media player at |timestamp|. | |
60 int64 buffered_bytes; | |
61 // Time at which buffering measurement was taken. | |
62 base::Time timestamp; | |
63 }; | |
64 | |
65 // Represents a span of time in which the media was buffering data. | |
66 class Sample { | |
67 public: | |
68 Sample(); | |
69 Sample(const BufferingPoint& start, const BufferingPoint& end); | |
70 | |
71 // Set the end point of the data sample. | |
72 void set_end(const BufferingPoint& new_end); | |
73 | |
74 const BufferingPoint& start() const { return start_; } | |
75 const BufferingPoint& end() const { return end_; } | |
76 | |
77 // Returns the bytes downloaded per second in this sample. Returns -1.0 if | |
78 // sample is invalid. | |
79 float bytes_per_second() const; | |
80 | |
81 // Returns the seconds elapsed in this sample. Returns -1.0 if the sample | |
82 // has not begun yet. | |
83 float seconds_elapsed() const; | |
84 | |
85 // Returns bytes downloaded in this sample. Returns -1.0 if the sample has | |
86 // not begun yet. | |
87 int64 bytes_downloaded() const; | |
88 | |
89 // Returns true if Sample has not been initialized. | |
90 bool is_null() const; | |
91 | |
92 // Resets the sample to an uninitialized state. | |
93 void Reset(); | |
94 | |
95 // Restarts the sample to begin its measurement at what was previously its | |
96 // end point. | |
97 void RestartAtEndBufferingPoint(); | |
98 | |
99 private: | |
100 BufferingPoint start_; | |
101 BufferingPoint end_; | |
102 }; | |
103 | |
104 int64 bytes_downloaded_in_window() const; | |
105 float seconds_elapsed_in_window() const; | |
106 | |
107 // Updates window with latest sample if it is ready. | |
108 void UpdateSampleWindow(); | |
109 | |
110 // Returns an approximation of the current download rate in bytes per second. | |
111 // Returns -1.0 if unknown. | |
112 float ApproximateDownloadByteRate() const; | |
113 | |
114 // Helper method that returns true if the monitor believes it should fire the | |
115 // |canplaythrough_cb_|. | |
116 bool ShouldNotifyCanPlayThrough(); | |
117 | |
118 // Examines the download rate and fires the |canplaythrough_cb_| callback if | |
119 // the monitor deems it the right time. | |
120 void NotifyCanPlayThroughIfNeeded(); | |
121 | |
122 // Callback to run when the monitor believes the media can play through | |
123 // without needing to pause to buffer. | |
124 CanPlayThroughCB canplaythrough_cb_; | |
125 | |
126 // Indicates whether the monitor has run the |canplaythrough_cb_|. | |
127 bool has_notified_can_play_through_; | |
128 | |
129 // Measurements used to approximate download speed. | |
130 Sample current_sample_; | |
131 std::deque<Sample> sample_window_; | |
132 | |
133 // True if actively downloading bytes, false otherwise. | |
134 bool is_downloading_data_; | |
135 | |
136 // Total number of bytes in the media file, 0 if unknown or undefined. | |
137 int64 total_bytes_; | |
138 | |
139 // Amount of bytes buffered. | |
140 int64 buffered_bytes_; | |
141 | |
142 // True if the media file is a fully loaded source, e.g. file:// protocol. | |
143 bool loaded_; | |
144 | |
145 // Bitrate of the media file, 0 if unknown. | |
146 int bitrate_; | |
147 | |
148 // True if the monitor has not yet started or has been stopped, false | |
149 // otherwise. | |
150 bool stopped_; | |
151 | |
152 DISALLOW_COPY_AND_ASSIGN(DownloadRateMonitor); | |
153 }; | |
154 | |
155 } // namespace media | |
156 | |
157 #endif // MEDIA_BASE_DOWNLOAD_RATE_MONITOR_H_ | |
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