Fixit: Move tab and desktop capture code to new location.

content/browser/renderer_host/media/video_capture_oracle.cc

-// Copyright (c) 2013 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 "content/browser/renderer_host/media/video_capture_oracle.h"
-
-#include "base/debug/trace_event.h"
-
-namespace content {
-
-namespace {
-
-// This value controls how many redundant, timer-base captures occur when the
-// content is static. Redundantly capturing the same frame allows iterative
-// quality enhancement, and also allows the buffer to fill in "buffered mode".
-//
-// TODO(nick): Controlling this here is a hack and a layering violation, since
-// it's a strategy specific to the WebRTC consumer, and probably just papers
-// over some frame dropping and quality bugs. It should either be controlled at
-// a higher level, or else redundant frame generation should be pushed down
-// further into the WebRTC encoding stack.
-const int kNumRedundantCapturesOfStaticContent = 200;
-
-}  // anonymous namespace
-
-VideoCaptureOracle::VideoCaptureOracle(base::TimeDelta capture_period,
-                                       bool events_are_reliable)
-    : capture_period_(capture_period),
-      frame_number_(0),
-      last_delivered_frame_number_(0),
-      sampler_(capture_period_,
-               events_are_reliable,
-               kNumRedundantCapturesOfStaticContent) {}
-
-bool VideoCaptureOracle::ObserveEventAndDecideCapture(
-    Event event,
-    base::TimeTicks event_time) {
-  // Record |event| and decide whether it's a good time to capture.
-  const bool content_is_dirty = (event == kCompositorUpdate ||
-                                 event == kSoftwarePaint);
-  bool should_sample;
-  if (content_is_dirty) {
-    frame_number_++;
-    should_sample = sampler_.AddEventAndConsiderSampling(event_time);
-  } else {
-    should_sample = sampler_.IsOverdueForSamplingAt(event_time);
-  }
-  return should_sample;
-}
-
-int VideoCaptureOracle::RecordCapture() {
-  sampler_.RecordSample();
-  return frame_number_;
-}
-
-bool VideoCaptureOracle::CompleteCapture(int frame_number,
-                                         base::TimeTicks timestamp) {
-  // Drop frame if previous frame number is higher or we're trying to deliver
-  // a frame with the same timestamp.
-  if (last_delivered_frame_number_ > frame_number ||
-      last_delivered_frame_timestamp_ == timestamp) {
-    LOG(ERROR) << "Frame with same timestamp or out of order delivery. "
-               << "Dropping frame.";
-    return false;
-  }
-
-  if (last_delivered_frame_timestamp_ > timestamp) {
-    // We should not get here unless time was adjusted backwards.
-    LOG(ERROR) << "Frame with past timestamp (" << timestamp.ToInternalValue()
-               << ") was delivered";
-  }
-
-  last_delivered_frame_number_ = frame_number;
-  last_delivered_frame_timestamp_ = timestamp;
-
-  return true;
-}
-
-SmoothEventSampler::SmoothEventSampler(base::TimeDelta capture_period,
-                                       bool events_are_reliable,
-                                       int redundant_capture_goal)
-    :  events_are_reliable_(events_are_reliable),
-       capture_period_(capture_period),
-       redundant_capture_goal_(redundant_capture_goal),
-       token_bucket_capacity_(capture_period + capture_period / 2),
-       overdue_sample_count_(0),
-       token_bucket_(token_bucket_capacity_) {
-  DCHECK_GT(capture_period_.InMicroseconds(), 0);
-}
-
-bool SmoothEventSampler::AddEventAndConsiderSampling(
-    base::TimeTicks event_time) {
-  DCHECK(!event_time.is_null());
-
-  // Add tokens to the bucket based on advancement in time.  Then, re-bound the
-  // number of tokens in the bucket.  Overflow occurs when there is too much
-  // time between events (a common case), or when RecordSample() is not being
-  // called often enough (a bug).  On the other hand, if RecordSample() is being
-  // called too often (e.g., as a reaction to IsOverdueForSamplingAt()), the
-  // bucket will underflow.
-  if (!current_event_.is_null()) {
-    if (current_event_ < event_time) {
-      token_bucket_ += event_time - current_event_;
-      if (token_bucket_ > token_bucket_capacity_)
-        token_bucket_ = token_bucket_capacity_;
-    }
-    // Side note: If the system clock is reset, causing |current_event_| to be
-    // greater than |event_time|, everything here will simply gracefully adjust.
-    if (token_bucket_ < base::TimeDelta())
-      token_bucket_ = base::TimeDelta();
-    TRACE_COUNTER1("mirroring",
-                   "MirroringTokenBucketUsec", token_bucket_.InMicroseconds());
-  }
-  current_event_ = event_time;
-
-  // Return true if one capture period's worth of tokens are in the bucket.
-  return token_bucket_ >= capture_period_;
-}
-
-void SmoothEventSampler::RecordSample() {
-  token_bucket_ -= capture_period_;
-  TRACE_COUNTER1("mirroring",
-                 "MirroringTokenBucketUsec", token_bucket_.InMicroseconds());
-
-  bool was_paused = overdue_sample_count_ == redundant_capture_goal_;
-  if (HasUnrecordedEvent()) {
-    last_sample_ = current_event_;
-    overdue_sample_count_ = 0;
-  } else {
-    ++overdue_sample_count_;
-  }
-  bool is_paused = overdue_sample_count_ == redundant_capture_goal_;
-
-  VLOG_IF(0, !was_paused && is_paused)
-      << "Tab content unchanged for " << redundant_capture_goal_
-      << " frames; capture will halt until content changes.";
-  VLOG_IF(0, was_paused && !is_paused)
-      << "Content changed; capture will resume.";
-}
-
-bool SmoothEventSampler::IsOverdueForSamplingAt(base::TimeTicks event_time)
-    const {
-  DCHECK(!event_time.is_null());
-
-  // If we don't get events on compositor updates on this platform, then we
-  // don't reliably know whether we're dirty.
-  if (events_are_reliable_) {
-    if (!HasUnrecordedEvent() &&
-        overdue_sample_count_ >= redundant_capture_goal_) {
-      return false;  // Not dirty.
-    }
-  }
-
-  if (last_sample_.is_null())
-    return true;
-
-  // If we're dirty but not yet old, then we've recently gotten updates, so we
-  // won't request a sample just yet.
-  base::TimeDelta dirty_interval = event_time - last_sample_;
-  if (dirty_interval < capture_period_ * 4)
-    return false;
-  else
-    return true;
-}
-
-bool SmoothEventSampler::HasUnrecordedEvent() const {
-  return !current_event_.is_null() && current_event_ != last_sample_;
-}
-
-}  // namespace content