Move VP9 frame rate controller to separate class.

Bug: webrtc:9669
Change-Id: I6f30587778e9783182af11d2410464024918e171
Reviewed-on: https://webrtc-review.googlesource.com/96201
Commit-Queue: Sergey Silkin <ssilkin@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24487}

modules/video_coding/utility/framerate_controller.cc

@@ -0,0 +1,81 @@
+/*
+ *  Copyright (c) 2018 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "modules/video_coding/utility/framerate_controller.h"
+
+#include "rtc_base/checks.h"
+
+namespace webrtc {
+
+FramerateController::FramerateController(float target_framerate_fps)
+    : min_frame_interval_ms_(0), framerate_estimator_(1000.0, 1000.0) {
+  SetTargetRate(target_framerate_fps);
+}
+
+void FramerateController::SetTargetRate(float target_framerate_fps) {
+  if (target_framerate_fps_ != target_framerate_fps) {
+    framerate_estimator_.Reset();
+    if (last_timestamp_ms_) {
+      framerate_estimator_.Update(1, *last_timestamp_ms_);
+    }
+
+    const size_t target_frame_interval_ms = 1000 / target_framerate_fps;
+    target_framerate_fps_ = target_framerate_fps;
+    min_frame_interval_ms_ = 85 * target_frame_interval_ms / 100;
+  }
+}
+
+float FramerateController::GetTargetRate() {
+  return *target_framerate_fps_;
+}
+
+void FramerateController::Reset() {
+  framerate_estimator_.Reset();
+  last_timestamp_ms_.reset();
+}
+
+bool FramerateController::DropFrame(uint32_t timestamp_ms) const {
+  if (timestamp_ms < last_timestamp_ms_) {
+    // Timestamp jumps backward. We can't make adequate drop decision. Don't
+    // drop this frame. Stats will be reset in AddFrame().
+    return false;
+  }
+
+  if (Rate(timestamp_ms).value_or(*target_framerate_fps_) >
+      target_framerate_fps_) {
+    return true;
+  }
+
+  if (last_timestamp_ms_) {
+    const int64_t diff_ms =
+        static_cast<int64_t>(timestamp_ms) - *last_timestamp_ms_;
+    if (diff_ms < min_frame_interval_ms_) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+void FramerateController::AddFrame(uint32_t timestamp_ms) {
+  if (timestamp_ms < last_timestamp_ms_) {
+    // Timestamp jumps backward.
+    Reset();
+  }
+
+  framerate_estimator_.Update(1, timestamp_ms);
+  last_timestamp_ms_ = timestamp_ms;
+}
+
+absl::optional<float> FramerateController::Rate(uint32_t timestamp_ms) const {
+  return framerate_estimator_.Rate(timestamp_ms);
+}
+
+}  // namespace webrtc