1 files changed, 60 insertions, 0 deletions
diff --git a/third_party/libwebrtc/video/frame_decode_timing.cc b/third_party/libwebrtc/video/frame_decode_timing.cc
new file mode 100644
index 0000000000..58ecd41c9e
--- /dev/null
+++ b/third_party/libwebrtc/video/frame_decode_timing.cc
@@ -0,0 +1,60 @@
+/*
+ *  Copyright (c) 2022 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 "video/frame_decode_timing.h"
+
+#include <algorithm>
+
+#include "absl/types/optional.h"
+#include "api/units/time_delta.h"
+#include "rtc_base/logging.h"
+
+namespace webrtc {
+
+FrameDecodeTiming::FrameDecodeTiming(Clock* clock,
+                                     webrtc::VCMTiming const* timing)
+    : clock_(clock), timing_(timing) {
+  RTC_DCHECK(clock_);
+  RTC_DCHECK(timing_);
+}
+
+absl::optional<FrameDecodeTiming::FrameSchedule>
+FrameDecodeTiming::OnFrameBufferUpdated(uint32_t next_temporal_unit_rtp,
+                                        uint32_t last_temporal_unit_rtp,
+                                        TimeDelta max_wait_for_frame,
+                                        bool too_many_frames_queued) {
+  RTC_DCHECK_GE(max_wait_for_frame, TimeDelta::Zero());
+  const Timestamp now = clock_->CurrentTime();
+  Timestamp render_time = timing_->RenderTime(next_temporal_unit_rtp, now);
+  TimeDelta max_wait =
+      timing_->MaxWaitingTime(render_time, now, too_many_frames_queued);
+
+  // If the delay is not too far in the past, or this is the last decodable
+  // frame then it is the best frame to be decoded. Otherwise, fast-forward
+  // to the next frame in the buffer.
+  if (max_wait <= -kMaxAllowedFrameDelay &&
+      next_temporal_unit_rtp != last_temporal_unit_rtp) {
+    RTC_DLOG(LS_VERBOSE) << "Fast-forwarded frame " << next_temporal_unit_rtp
+                         << " render time " << render_time << " with delay "
+                         << max_wait;
+    return absl::nullopt;
+  }
+
+  max_wait.Clamp(TimeDelta::Zero(), max_wait_for_frame);
+  RTC_DLOG(LS_VERBOSE) << "Selected frame with rtp " << next_temporal_unit_rtp
+                       << " render time " << render_time
+                       << " with a max wait of " << max_wait_for_frame
+                       << " clamped to " << max_wait;
+  Timestamp latest_decode_time = now + max_wait;
+  return FrameSchedule{.latest_decode_time = latest_decode_time,
+                       .render_time = render_time};
+}
+
+}  // namespace webrtc