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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. | 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 | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #include "webkit/glue/media/buffered_resource_loader.h" | 5 #include "webkit/glue/media/buffered_resource_loader.h" |
6 | 6 |
7 #include "base/format_macros.h" | 7 #include "base/format_macros.h" |
8 #include "base/stringprintf.h" | 8 #include "base/stringprintf.h" |
9 #include "base/string_util.h" | 9 #include "base/string_util.h" |
10 #include "media/base/media_log.h" | 10 #include "media/base/media_log.h" |
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28 using webkit_glue::MultipartResponseDelegate; | 28 using webkit_glue::MultipartResponseDelegate; |
29 | 29 |
30 namespace webkit_glue { | 30 namespace webkit_glue { |
31 | 31 |
32 static const int kHttpOK = 200; | 32 static const int kHttpOK = 200; |
33 static const int kHttpPartialContent = 206; | 33 static const int kHttpPartialContent = 206; |
34 | 34 |
35 // Define the number of bytes in a megabyte. | 35 // Define the number of bytes in a megabyte. |
36 static const size_t kMegabyte = 1024 * 1024; | 36 static const size_t kMegabyte = 1024 * 1024; |
37 | 37 |
38 // Default backward capacity of the buffer. | 38 // Minimum capacity of the buffer in forward or backward direction. |
39 static const size_t kBackwardCapacity = 2 * kMegabyte; | 39 // |
40 | 40 // 2MB is an arbitrary limit; it just seems to be "good enough" in practice. |
41 // Default forward capacity of the buffer. | 41 static const size_t kMinBufferCapacity = 2 * kMegabyte; |
42 static const size_t kForwardCapacity = 10 * kMegabyte; | |
43 | 42 |
44 // Maximum capacity of the buffer in forward or backward direction. This is | 43 // Maximum capacity of the buffer in forward or backward direction. This is |
45 // effectively the largest single read the code path can handle. | 44 // effectively the largest single read the code path can handle. |
46 // 20MB is an arbitrary limit; it just seems to be "good enough" in practice. | 45 // 20MB is an arbitrary limit; it just seems to be "good enough" in practice. |
47 static const size_t kMaxBufferCapacity = 20 * kMegabyte; | 46 static const size_t kMaxBufferCapacity = 20 * kMegabyte; |
48 | 47 |
49 // Maximum number of bytes outside the buffer we will wait for in order to | 48 // Maximum number of bytes outside the buffer we will wait for in order to |
50 // fulfill a read. If a read starts more than 2MB away from the data we | 49 // fulfill a read. If a read starts more than 2MB away from the data we |
51 // currently have in the buffer, we will not wait for buffer to reach the read's | 50 // currently have in the buffer, we will not wait for buffer to reach the read's |
52 // location and will instead reset the request. | 51 // location and will instead reset the request. |
53 static const int kForwardWaitThreshold = 2 * kMegabyte; | 52 static const int kForwardWaitThreshold = 2 * kMegabyte; |
54 | 53 |
| 54 // Computes the suggested backward and forward capacity for the buffer |
| 55 // if one wants to play at |playback_rate| * the natural playback speed. |
| 56 // Use a value of 0 for |bitrate| if it is unknown. |
| 57 static void ComputeTargetBufferWindow(float playback_rate, int bitrate, |
| 58 size_t* out_backward_capacity, |
| 59 size_t* out_forward_capacity) { |
| 60 static const size_t kDefaultBitrate = 200 * 1024 * 8; // 200 Kbps. |
| 61 static const size_t kMaxBitrate = 20 * kMegabyte * 8; // 20 Mbps. |
| 62 static const float kMaxPlaybackRate = 25.0; |
| 63 static const size_t kTargetSecondsBufferedAhead = 10; |
| 64 static const size_t kTargetSecondsBufferedBehind = 2; |
| 65 |
| 66 // Use a default bit rate if unknown and clamp to prevent overflow. |
| 67 if (bitrate <= 0) |
| 68 bitrate = kDefaultBitrate; |
| 69 bitrate = std::min(static_cast<size_t>(bitrate), kMaxBitrate); |
| 70 |
| 71 // Only scale the buffer window for playback rates greater than 1.0 in |
| 72 // magnitude and clamp to prevent overflow. |
| 73 bool backward_playback = false; |
| 74 if (playback_rate < 0.0f) { |
| 75 backward_playback = true; |
| 76 playback_rate *= -1.0f; |
| 77 } |
| 78 |
| 79 playback_rate = std::max(playback_rate, 1.0f); |
| 80 playback_rate = std::min(playback_rate, kMaxPlaybackRate); |
| 81 |
| 82 size_t bytes_per_second = static_cast<size_t>(playback_rate * bitrate / 8.0); |
| 83 |
| 84 // Clamp between kMinBufferCapacity and kMaxBufferCapacity. |
| 85 *out_forward_capacity = std::max( |
| 86 kTargetSecondsBufferedAhead * bytes_per_second, kMinBufferCapacity); |
| 87 *out_backward_capacity = std::max( |
| 88 kTargetSecondsBufferedBehind * bytes_per_second, kMinBufferCapacity); |
| 89 |
| 90 *out_forward_capacity = std::min(*out_forward_capacity, kMaxBufferCapacity); |
| 91 *out_backward_capacity = std::min(*out_backward_capacity, kMaxBufferCapacity); |
| 92 |
| 93 if (backward_playback) |
| 94 std::swap(*out_forward_capacity, *out_backward_capacity); |
| 95 } |
| 96 |
| 97 |
55 BufferedResourceLoader::BufferedResourceLoader( | 98 BufferedResourceLoader::BufferedResourceLoader( |
56 const GURL& url, | 99 const GURL& url, |
57 int64 first_byte_position, | 100 int64 first_byte_position, |
58 int64 last_byte_position, | 101 int64 last_byte_position, |
| 102 DeferStrategy strategy, |
| 103 int bitrate, |
| 104 float playback_rate, |
59 media::MediaLog* media_log) | 105 media::MediaLog* media_log) |
60 : buffer_(new media::SeekableBuffer(kBackwardCapacity, kForwardCapacity)), | 106 : deferred_(false), |
61 deferred_(false), | 107 defer_strategy_(strategy), |
62 defer_strategy_(kReadThenDefer), | |
63 completed_(false), | 108 completed_(false), |
64 range_requested_(false), | 109 range_requested_(false), |
65 range_supported_(false), | 110 range_supported_(false), |
66 saved_forward_capacity_(0), | 111 saved_forward_capacity_(0), |
67 url_(url), | 112 url_(url), |
68 first_byte_position_(first_byte_position), | 113 first_byte_position_(first_byte_position), |
69 last_byte_position_(last_byte_position), | 114 last_byte_position_(last_byte_position), |
70 single_origin_(true), | 115 single_origin_(true), |
71 start_callback_(NULL), | 116 start_callback_(NULL), |
72 offset_(0), | 117 offset_(0), |
73 content_length_(kPositionNotSpecified), | 118 content_length_(kPositionNotSpecified), |
74 instance_size_(kPositionNotSpecified), | 119 instance_size_(kPositionNotSpecified), |
75 read_callback_(NULL), | 120 read_callback_(NULL), |
76 read_position_(0), | 121 read_position_(0), |
77 read_size_(0), | 122 read_size_(0), |
78 read_buffer_(NULL), | 123 read_buffer_(NULL), |
79 first_offset_(0), | 124 first_offset_(0), |
80 last_offset_(0), | 125 last_offset_(0), |
81 keep_test_loader_(false), | 126 keep_test_loader_(false), |
82 bitrate_(0), | 127 bitrate_(bitrate), |
83 playback_rate_(0.0), | 128 playback_rate_(playback_rate), |
84 media_log_(media_log) { | 129 media_log_(media_log) { |
| 130 |
| 131 size_t backward_capacity; |
| 132 size_t forward_capacity; |
| 133 ComputeTargetBufferWindow( |
| 134 playback_rate_, bitrate_, &backward_capacity, &forward_capacity); |
| 135 buffer_.reset(new media::SeekableBuffer(backward_capacity, forward_capacity)); |
85 } | 136 } |
86 | 137 |
87 BufferedResourceLoader::~BufferedResourceLoader() { | 138 BufferedResourceLoader::~BufferedResourceLoader() { |
88 if (!completed_ && url_loader_.get()) | 139 if (!completed_ && url_loader_.get()) |
89 url_loader_->cancel(); | 140 url_loader_->cancel(); |
90 } | 141 } |
91 | 142 |
92 void BufferedResourceLoader::Start(net::OldCompletionCallback* start_callback, | 143 void BufferedResourceLoader::Start(net::OldCompletionCallback* start_callback, |
93 const base::Closure& event_callback, | 144 const base::Closure& event_callback, |
94 WebFrame* frame) { | 145 WebFrame* frame) { |
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225 | 276 |
226 // If we expect the read request to be fulfilled later, return | 277 // If we expect the read request to be fulfilled later, return |
227 // and let more data to flow in. | 278 // and let more data to flow in. |
228 if (WillFulfillRead()) { | 279 if (WillFulfillRead()) { |
229 // If necessary, expand the forward capacity of the buffer to accomodate an | 280 // If necessary, expand the forward capacity of the buffer to accomodate an |
230 // unusually large read. | 281 // unusually large read. |
231 if (read_size_ > buffer_->forward_capacity()) { | 282 if (read_size_ > buffer_->forward_capacity()) { |
232 saved_forward_capacity_ = buffer_->forward_capacity(); | 283 saved_forward_capacity_ = buffer_->forward_capacity(); |
233 buffer_->set_forward_capacity(read_size_); | 284 buffer_->set_forward_capacity(read_size_); |
234 } | 285 } |
235 return; | 286 return; |
236 } | 287 } |
237 | 288 |
238 // Make a callback to report failure. | 289 // Make a callback to report failure. |
239 DoneRead(net::ERR_CACHE_MISS); | 290 DoneRead(net::ERR_CACHE_MISS); |
240 } | 291 } |
241 | 292 |
242 int64 BufferedResourceLoader::GetBufferedPosition() { | 293 int64 BufferedResourceLoader::GetBufferedPosition() { |
243 if (buffer_.get()) | 294 if (buffer_.get()) |
244 return offset_ + static_cast<int>(buffer_->forward_bytes()) - 1; | 295 return offset_ + static_cast<int>(buffer_->forward_bytes()) - 1; |
245 return kPositionNotSpecified; | 296 return kPositionNotSpecified; |
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491 return single_origin_; | 542 return single_origin_; |
492 } | 543 } |
493 | 544 |
494 void BufferedResourceLoader::UpdateDeferStrategy(DeferStrategy strategy) { | 545 void BufferedResourceLoader::UpdateDeferStrategy(DeferStrategy strategy) { |
495 defer_strategy_ = strategy; | 546 defer_strategy_ = strategy; |
496 UpdateDeferBehavior(); | 547 UpdateDeferBehavior(); |
497 } | 548 } |
498 | 549 |
499 void BufferedResourceLoader::SetPlaybackRate(float playback_rate) { | 550 void BufferedResourceLoader::SetPlaybackRate(float playback_rate) { |
500 playback_rate_ = playback_rate; | 551 playback_rate_ = playback_rate; |
| 552 |
| 553 // This is a pause so don't bother updating the buffer window as we'll likely |
| 554 // get unpaused in the future. |
| 555 if (playback_rate_ == 0.0) |
| 556 return; |
| 557 |
501 UpdateBufferWindow(); | 558 UpdateBufferWindow(); |
502 } | 559 } |
503 | 560 |
504 void BufferedResourceLoader::SetBitrate(int bitrate) { | 561 void BufferedResourceLoader::SetBitrate(int bitrate) { |
505 DCHECK(bitrate >= 0); | 562 DCHECK(bitrate >= 0); |
506 bitrate_ = bitrate; | 563 bitrate_ = bitrate; |
507 UpdateBufferWindow(); | 564 UpdateBufferWindow(); |
508 } | 565 } |
509 | 566 |
510 ///////////////////////////////////////////////////////////////////////////// | 567 ///////////////////////////////////////////////////////////////////////////// |
511 // Helper methods. | 568 // Helper methods. |
512 | 569 |
513 // Computes the suggested backward and forward capacity for the buffer | |
514 // if one wants to play at |playback_rate| * the natural playback speed. | |
515 // Use a value of 0 for |bitrate| if it is unknown. | |
516 static void ComputeTargetBufferWindow(float playback_rate, int bitrate, | |
517 size_t* out_backward_capacity, | |
518 size_t* out_forward_capacity) { | |
519 DCHECK_GE(bitrate, 0); | |
520 DCHECK_NE(playback_rate, 0.0); | |
521 static const size_t kDefaultBitrate = kMegabyte; | |
522 static const size_t kMaxBitrate = 50 * kMegabyte; | |
523 static const float kMaxPlaybackRate = 25.0; | |
524 static const size_t kTargetSecondsBufferedAhead = 10; | |
525 static const size_t kTargetSecondsBufferedBehind = 2; | |
526 | |
527 if (bitrate <= 0) | |
528 bitrate = kDefaultBitrate; | |
529 | |
530 bool backward_playback = playback_rate < 0.0; | |
531 if (backward_playback) | |
532 playback_rate *= -1.0; | |
533 | |
534 // Cap playback rate and bitrate to prevent overflow. | |
535 playback_rate = std::min(kMaxPlaybackRate, playback_rate); | |
536 bitrate = std::min(kMaxBitrate, static_cast<size_t>(bitrate)); | |
537 | |
538 size_t bytes_per_second = static_cast<size_t>(playback_rate * bitrate / 8.0); | |
539 | |
540 *out_forward_capacity = std::min( | |
541 kTargetSecondsBufferedAhead * bytes_per_second, kMaxBufferCapacity); | |
542 *out_backward_capacity = std::min( | |
543 kTargetSecondsBufferedBehind * bytes_per_second, kMaxBufferCapacity); | |
544 if (backward_playback) | |
545 std::swap(*out_forward_capacity, *out_backward_capacity); | |
546 } | |
547 | |
548 void BufferedResourceLoader::UpdateBufferWindow() { | 570 void BufferedResourceLoader::UpdateBufferWindow() { |
549 if (!buffer_.get()) | 571 if (!buffer_.get()) |
550 return; | 572 return; |
551 | 573 |
552 // Don't adjust buffer window if video is paused. | |
553 if (playback_rate_ == 0.0) | |
554 return; | |
555 | |
556 size_t backward_capacity; | 574 size_t backward_capacity; |
557 size_t forward_capacity; | 575 size_t forward_capacity; |
558 ComputeTargetBufferWindow( | 576 ComputeTargetBufferWindow( |
559 playback_rate_, bitrate_, &backward_capacity, &forward_capacity); | 577 playback_rate_, bitrate_, &backward_capacity, &forward_capacity); |
560 | 578 |
561 // This does not evict data from the buffer if the new capacities are less | 579 // This does not evict data from the buffer if the new capacities are less |
562 // than the current capacities; the new limits will be enforced after the | 580 // than the current capacities; the new limits will be enforced after the |
563 // existing excess buffered data is consumed. | 581 // existing excess buffered data is consumed. |
564 buffer_->set_backward_capacity(backward_capacity); | 582 buffer_->set_backward_capacity(backward_capacity); |
565 buffer_->set_forward_capacity(forward_capacity); | 583 buffer_->set_forward_capacity(forward_capacity); |
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771 if (buffer_.get()) { | 789 if (buffer_.get()) { |
772 media_log_->AddEvent( | 790 media_log_->AddEvent( |
773 media_log_->CreateBufferedExtentsChangedEvent( | 791 media_log_->CreateBufferedExtentsChangedEvent( |
774 offset_ - buffer_->backward_bytes(), | 792 offset_ - buffer_->backward_bytes(), |
775 offset_, | 793 offset_, |
776 offset_ + buffer_->forward_bytes())); | 794 offset_ + buffer_->forward_bytes())); |
777 } | 795 } |
778 } | 796 } |
779 | 797 |
780 } // namespace webkit_glue | 798 } // namespace webkit_glue |
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