Delete DownloadRateMonitor since it's never worked right.

media/base/download_rate_monitor.cc

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "media/base/download_rate_monitor.h"
-
-#include "base/bind.h"
-#include "base/time.h"
-
-namespace media {
-
-// Number of samples to use to collect and average for each measurement of
-// download rate.
-static const size_t kNumberOfSamples = 5;
-
-// Minimum number of seconds represented in a sample period.
-static const float kSamplePeriod = 1.0;
-
-DownloadRateMonitor::Sample::Sample() {
-  Reset();
-}
-
-DownloadRateMonitor::Sample::~Sample() { }
-
-DownloadRateMonitor::Sample::Sample(
-    const BufferingPoint& start, const BufferingPoint& end) {
-  Reset();
-  start_ = start;
-  set_end(end);
-}
-
-void DownloadRateMonitor::Sample::set_end(const BufferingPoint& new_end) {
-  DCHECK(!start_.timestamp.is_null());
-  DCHECK(new_end.buffered_bytes >= start_.buffered_bytes);
-  DCHECK(new_end.timestamp >= start_.timestamp);
-  end_ = new_end;
-}
-
-float DownloadRateMonitor::Sample::bytes_per_second() const {
-  if (seconds_elapsed() > 0.0 && bytes_downloaded() >= 0)
-    return bytes_downloaded() / seconds_elapsed();
-  return -1.0;
-}
-
-float DownloadRateMonitor::Sample::seconds_elapsed() const {
-  if (start_.timestamp.is_null() || end_.timestamp.is_null())
-    return -1.0;
-  return (end_.timestamp - start_.timestamp).InSecondsF();
-}
-
-int64 DownloadRateMonitor::Sample::bytes_downloaded() const {
-  if (start_.timestamp.is_null() || end_.timestamp.is_null())
-    return -1.0;
-  return end_.buffered_bytes - start_.buffered_bytes;
-}
-
-bool DownloadRateMonitor::Sample::is_null() const {
-  return start_.timestamp.is_null() && end_.timestamp.is_null();
-}
-
-void DownloadRateMonitor::Sample::Reset() {
-  start_ = BufferingPoint();
-  end_ = BufferingPoint();
-}
-
-void DownloadRateMonitor::Sample::RestartAtEndBufferingPoint() {
-  start_ = end_;
-  end_ = BufferingPoint();
-}
-
-DownloadRateMonitor::DownloadRateMonitor() {
-  Reset();
-}
-
-void DownloadRateMonitor::Start(
-    const base::Closure& canplaythrough_cb, int media_bitrate,
-    bool streaming, bool local_source) {
-  canplaythrough_cb_ = canplaythrough_cb;
-  streaming_ = streaming;
-  local_source_ = local_source;
-  stopped_ = false;
-  bitrate_ = media_bitrate;
-  current_sample_.Reset();
-  buffered_bytes_ = 0;
-
-  NotifyCanPlayThroughIfNeeded();
-}
-
-void DownloadRateMonitor::SetBufferedBytes(
-    int64 buffered_bytes, const base::Time& timestamp) {
-  if (stopped_)
-    return;
-
-  is_downloading_data_ = true;
-
-  // Check monotonically nondecreasing constraint.
-  base::Time previous_time;
-  if (!current_sample_.is_null())
-    previous_time = current_sample_.end().timestamp;
-  else if (!sample_window_.empty())
-    previous_time = sample_window_.back().end().timestamp;
-
-  // If we go backward in time, dismiss the sample.
-  if (!previous_time.is_null() && timestamp < previous_time)
-    return;
-
-  // If the buffer level has dropped, invalidate current sample.
-  if (buffered_bytes < buffered_bytes_)
-    current_sample_.Reset();
-  buffered_bytes_ = buffered_bytes;
-
-  BufferingPoint latest_point = { buffered_bytes, timestamp };
-  if (current_sample_.is_null())
-    current_sample_ = Sample(latest_point, latest_point);
-  else
-    current_sample_.set_end(latest_point);
-
-  UpdateSampleWindow();
-  NotifyCanPlayThroughIfNeeded();
-}
-
-void DownloadRateMonitor::SetNetworkActivity(bool is_downloading_data) {
-  if (is_downloading_data == is_downloading_data_)
-    return;
-  // Invalidate the current sample if downloading is going from start to stopped
-  // or vice versa.
-  current_sample_.Reset();
-  is_downloading_data_ = is_downloading_data;
-}
-
-void DownloadRateMonitor::Stop() {
-  stopped_ = true;
-  current_sample_.Reset();
-  buffered_bytes_ = 0;
-}
-
-void DownloadRateMonitor::Reset() {
-  canplaythrough_cb_.Reset();
-  has_notified_can_play_through_ = false;
-  current_sample_.Reset();
-  sample_window_.clear();
-  is_downloading_data_ = false;
-  total_bytes_ = -1;
-  buffered_bytes_ = 0;
-  local_source_ = false;
-  bitrate_ = 0;
-  stopped_ = true;
-  streaming_ = false;
-}
-
-DownloadRateMonitor::~DownloadRateMonitor() { }
-
-int64 DownloadRateMonitor::bytes_downloaded_in_window() const {
-  // There are max |kNumberOfSamples| so we might as well recompute each time.
-  int64 total = 0;
-  for (size_t i = 0; i < sample_window_.size(); ++i)
-    total += sample_window_[i].bytes_downloaded();
-  return total;
-}
-
-float DownloadRateMonitor::seconds_elapsed_in_window() const {
-  // There are max |kNumberOfSamples| so we might as well recompute each time.
-  float total = 0.0;
-  for (size_t i = 0; i < sample_window_.size(); ++i)
-    total += sample_window_[i].seconds_elapsed();
-  return total;
-}
-
-void DownloadRateMonitor::UpdateSampleWindow() {
-  if (current_sample_.seconds_elapsed() < kSamplePeriod)
-    return;
-
-  // Add latest sample and remove oldest sample.
-  sample_window_.push_back(current_sample_);
-  if (sample_window_.size() > kNumberOfSamples)
-    sample_window_.pop_front();
-
-  // Prepare for next measurement.
-  current_sample_.RestartAtEndBufferingPoint();
-}
-
-float DownloadRateMonitor::ApproximateDownloadByteRate() const {
-  // Compute and return the average download byte rate from within the sample
-  // window.
-  // NOTE: In the unlikely case where the data is arriving really bursty-ly,
-  // say getting a big chunk of data every 5 seconds, then with this
-  // implementation it will take 25 seconds until bitrate is calculated.
-  if (sample_window_.size() >= kNumberOfSamples &&
-      seconds_elapsed_in_window() > 0.0) {
-    return bytes_downloaded_in_window() / seconds_elapsed_in_window();
-  }
-
-  // Could not determine approximate download byte rate.
-  return -1.0;
-}
-
-bool DownloadRateMonitor::ShouldNotifyCanPlayThrough() {
-  if (stopped_)
-    return false;
-
-  // Only notify CanPlayThrough once for now.
-  if (has_notified_can_play_through_)
-    return false;
-
-  // Fire CanPlayThrough immediately if the source is local or streaming.
-  //
-  // NOTE: It is a requirement for CanPlayThrough to fire immediately if the
-  // source is local, but the choice to optimistically fire the event for any
-  // streaming media element is a design decision that may need to be tweaked.
-  if (local_source_ || streaming_)
-    return true;
-
-  // If all bytes are buffered, fire CanPlayThrough.
-  if (buffered_bytes_ == total_bytes_)
-    return true;
-
-  // If bitrate is unknown, optimistically fire CanPlayThrough immediately.
-  // This is so a video with an unknown bitrate with the "autoplay" attribute
-  // will not wait until the entire file is downloaded before playback begins.
-  if (bitrate_ <= 0)
-    return true;
-
-  float bytes_needed_per_second = bitrate_ / 8;
-  float download_rate = ApproximateDownloadByteRate();
-
-  // If we are downloading at or faster than the media's bitrate, then we can
-  // play through to the end of the media without stopping to buffer.
-  if (download_rate > 0)
-    return download_rate >= bytes_needed_per_second;
-
-  // If download rate is unknown, it may be because the media is being
-  // downloaded so fast that it cannot collect an adequate number of samples
-  // before the download gets deferred.
-  //
-  // To catch this case, we also look at how much data is being downloaded
-  // immediately after the download begins.
-  if (sample_window_.size() < kNumberOfSamples) {
-    int64 bytes_downloaded_since_start =
-        bytes_downloaded_in_window() + current_sample_.bytes_downloaded();
-    float seconds_elapsed_since_start =
-        seconds_elapsed_in_window() + current_sample_.seconds_elapsed();
-
-    // If we download 4 seconds of data in less than 2 seconds of time, we're
-    // probably downloading at a fast enough rate that we can play through.
-    // This is an arbitrary metric that will likely need tweaking.
-    if (seconds_elapsed_since_start < 2.0 &&
-        bytes_downloaded_since_start > 4.0 * bytes_needed_per_second) {
-      return true;
-    }
-  }
-
-  return false;
-}
-
-void DownloadRateMonitor::NotifyCanPlayThroughIfNeeded() {
-  if (ShouldNotifyCanPlayThrough() && !canplaythrough_cb_.is_null()) {
-    canplaythrough_cb_.Run();
-    has_notified_can_play_through_ = true;
-  }
-}
-
-}  // namespace media