1 files changed, 88 insertions, 0 deletions
diff --git a/third_party/libwebrtc/common_video/framerate_controller.cc b/third_party/libwebrtc/common_video/framerate_controller.cc
new file mode 100644
index 0000000000..23e9c70cbd
--- /dev/null
+++ b/third_party/libwebrtc/common_video/framerate_controller.cc
@@ -0,0 +1,88 @@
+/*
+ *  Copyright 2021 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 "common_video/framerate_controller.h"
+
+#include <limits>
+
+#include "rtc_base/time_utils.h"
+
+namespace webrtc {
+namespace {
+constexpr double kMinFramerate = 0.5;
+}  // namespace
+
+FramerateController::FramerateController()
+    : FramerateController(std::numeric_limits<double>::max()) {}
+
+FramerateController::FramerateController(double max_framerate)
+    : max_framerate_(max_framerate) {}
+
+FramerateController::~FramerateController() {}
+
+void FramerateController::SetMaxFramerate(double max_framerate) {
+  max_framerate_ = max_framerate;
+}
+
+double FramerateController::GetMaxFramerate() const {
+  return max_framerate_;
+}
+
+bool FramerateController::ShouldDropFrame(int64_t in_timestamp_ns) {
+  if (max_framerate_ < kMinFramerate)
+    return true;
+
+  // If `max_framerate_` is not set (i.e. maxdouble), `frame_interval_ns` is
+  // rounded to 0.
+  int64_t frame_interval_ns = rtc::kNumNanosecsPerSec / max_framerate_;
+  if (frame_interval_ns <= 0) {
+    // Frame rate throttling not enabled.
+    return false;
+  }
+
+  if (next_frame_timestamp_ns_) {
+    // Time until next frame should be outputted.
+    const int64_t time_until_next_frame_ns =
+        (*next_frame_timestamp_ns_ - in_timestamp_ns);
+    // Continue if timestamp is within expected range.
+    if (std::abs(time_until_next_frame_ns) < 2 * frame_interval_ns) {
+      // Drop if a frame shouldn't be outputted yet.
+      if (time_until_next_frame_ns > 0)
+        return true;
+      // Time to output new frame.
+      *next_frame_timestamp_ns_ += frame_interval_ns;
+      return false;
+    }
+  }
+
+  // First timestamp received or timestamp is way outside expected range, so
+  // reset. Set first timestamp target to just half the interval to prefer
+  // keeping frames in case of jitter.
+  next_frame_timestamp_ns_ = in_timestamp_ns + frame_interval_ns / 2;
+  return false;
+}
+
+void FramerateController::Reset() {
+  max_framerate_ = std::numeric_limits<double>::max();
+  next_frame_timestamp_ns_ = absl::nullopt;
+}
+
+void FramerateController::KeepFrame(int64_t in_timestamp_ns) {
+  if (ShouldDropFrame(in_timestamp_ns)) {
+    if (max_framerate_ < kMinFramerate)
+      return;
+
+    int64_t frame_interval_ns = rtc::kNumNanosecsPerSec / max_framerate_;
+    if (next_frame_timestamp_ns_)
+      *next_frame_timestamp_ns_ += frame_interval_ns;
+  }
+}
+
+}  // namespace webrtc