1 /* 2 * Copyright (c) 2011 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #include "modules/video_coding/timing/inter_frame_delay.h" 12 13 #include "absl/types/optional.h" 14 #include "api/units/frequency.h" 15 #include "api/units/time_delta.h" 16 #include "modules/include/module_common_types_public.h" 17 18 namespace webrtc { 19 20 namespace { 21 constexpr Frequency k90kHz = Frequency::KiloHertz(90); 22 } 23 InterFrameDelay()24InterFrameDelay::InterFrameDelay() { 25 Reset(); 26 } 27 28 // Resets the delay estimate. Reset()29void InterFrameDelay::Reset() { 30 prev_wall_clock_ = absl::nullopt; 31 prev_rtp_timestamp_unwrapped_ = 0; 32 } 33 34 // Calculates the delay of a frame with the given timestamp. 35 // This method is called when the frame is complete. CalculateDelay(uint32_t rtp_timestamp,Timestamp now)36absl::optional<TimeDelta> InterFrameDelay::CalculateDelay( 37 uint32_t rtp_timestamp, 38 Timestamp now) { 39 int64_t rtp_timestamp_unwrapped = unwrapper_.Unwrap(rtp_timestamp); 40 if (!prev_wall_clock_) { 41 // First set of data, initialization, wait for next frame. 42 prev_wall_clock_ = now; 43 prev_rtp_timestamp_unwrapped_ = rtp_timestamp_unwrapped; 44 return TimeDelta::Zero(); 45 } 46 47 // Account for reordering in jitter variance estimate in the future? 48 // Note that this also captures incomplete frames which are grabbed for 49 // decoding after a later frame has been complete, i.e. real packet losses. 50 uint32_t cropped_last = static_cast<uint32_t>(prev_rtp_timestamp_unwrapped_); 51 if (rtp_timestamp_unwrapped < prev_rtp_timestamp_unwrapped_ || 52 !IsNewerTimestamp(rtp_timestamp, cropped_last)) { 53 return absl::nullopt; 54 } 55 56 // Compute the compensated timestamp difference. 57 int64_t d_rtp_ticks = rtp_timestamp_unwrapped - prev_rtp_timestamp_unwrapped_; 58 TimeDelta dts = d_rtp_ticks / k90kHz; 59 TimeDelta dt = now - *prev_wall_clock_; 60 61 // frameDelay is the difference of dT and dTS -- i.e. the difference of the 62 // wall clock time difference and the timestamp difference between two 63 // following frames. 64 TimeDelta delay = dt - dts; 65 66 prev_rtp_timestamp_unwrapped_ = rtp_timestamp_unwrapped; 67 prev_wall_clock_ = now; 68 return delay; 69 } 70 71 } // namespace webrtc 72