1/*
2 *  Copyright (c) 2012 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 "webrtc/video_engine/stream_synchronization.h"
12
13#include <assert.h>
14#include <math.h>
15#include <stdlib.h>
16
17#include <algorithm>
18
19#include "webrtc/system_wrappers/interface/logging.h"
20
21namespace webrtc {
22
23static const int kMaxChangeMs = 80;
24static const int kMaxDeltaDelayMs = 10000;
25static const int kFilterLength = 4;
26// Minimum difference between audio and video to warrant a change.
27static const int kMinDeltaMs = 30;
28
29struct ViESyncDelay {
30  ViESyncDelay() {
31    extra_video_delay_ms = 0;
32    last_video_delay_ms = 0;
33    extra_audio_delay_ms = 0;
34    last_audio_delay_ms = 0;
35    network_delay = 120;
36  }
37
38  int extra_video_delay_ms;
39  int last_video_delay_ms;
40  int extra_audio_delay_ms;
41  int last_audio_delay_ms;
42  int network_delay;
43};
44
45StreamSynchronization::StreamSynchronization(int audio_channel_id,
46                                             int video_channel_id)
47    : channel_delay_(new ViESyncDelay),
48      audio_channel_id_(audio_channel_id),
49      video_channel_id_(video_channel_id),
50      base_target_delay_ms_(0),
51      avg_diff_ms_(0) {}
52
53StreamSynchronization::~StreamSynchronization() {
54  delete channel_delay_;
55}
56
57bool StreamSynchronization::ComputeRelativeDelay(
58    const Measurements& audio_measurement,
59    const Measurements& video_measurement,
60    int* relative_delay_ms) {
61  assert(relative_delay_ms);
62  if (audio_measurement.rtcp.size() < 2 || video_measurement.rtcp.size() < 2) {
63    // We need two RTCP SR reports per stream to do synchronization.
64    return false;
65  }
66  int64_t audio_last_capture_time_ms;
67  if (!RtpToNtpMs(audio_measurement.latest_timestamp,
68                  audio_measurement.rtcp,
69                  &audio_last_capture_time_ms)) {
70    return false;
71  }
72  int64_t video_last_capture_time_ms;
73  if (!RtpToNtpMs(video_measurement.latest_timestamp,
74                  video_measurement.rtcp,
75                  &video_last_capture_time_ms)) {
76    return false;
77  }
78  if (video_last_capture_time_ms < 0) {
79    return false;
80  }
81  // Positive diff means that video_measurement is behind audio_measurement.
82  *relative_delay_ms = video_measurement.latest_receive_time_ms -
83      audio_measurement.latest_receive_time_ms -
84      (video_last_capture_time_ms - audio_last_capture_time_ms);
85  if (*relative_delay_ms > kMaxDeltaDelayMs ||
86      *relative_delay_ms < -kMaxDeltaDelayMs) {
87    return false;
88  }
89  return true;
90}
91
92bool StreamSynchronization::ComputeDelays(int relative_delay_ms,
93                                          int current_audio_delay_ms,
94                                          int* total_audio_delay_target_ms,
95                                          int* total_video_delay_target_ms) {
96  assert(total_audio_delay_target_ms && total_video_delay_target_ms);
97
98  int current_video_delay_ms = *total_video_delay_target_ms;
99  LOG(LS_VERBOSE) << "Audio delay: " << current_audio_delay_ms
100                  << ", network delay diff: " << channel_delay_->network_delay
101                  << " current diff: " << relative_delay_ms
102                  << " for channel " << audio_channel_id_;
103  // Calculate the difference between the lowest possible video delay and
104  // the current audio delay.
105  int current_diff_ms = current_video_delay_ms - current_audio_delay_ms +
106      relative_delay_ms;
107
108  avg_diff_ms_ = ((kFilterLength - 1) * avg_diff_ms_ +
109      current_diff_ms) / kFilterLength;
110  if (abs(avg_diff_ms_) < kMinDeltaMs) {
111    // Don't adjust if the diff is within our margin.
112    return false;
113  }
114
115  // Make sure we don't move too fast.
116  int diff_ms = avg_diff_ms_ / 2;
117  diff_ms = std::min(diff_ms, kMaxChangeMs);
118  diff_ms = std::max(diff_ms, -kMaxChangeMs);
119
120  // Reset the average after a move to prevent overshooting reaction.
121  avg_diff_ms_ = 0;
122
123  if (diff_ms > 0) {
124    // The minimum video delay is longer than the current audio delay.
125    // We need to decrease extra video delay, or add extra audio delay.
126    if (channel_delay_->extra_video_delay_ms > base_target_delay_ms_) {
127      // We have extra delay added to ViE. Reduce this delay before adding
128      // extra delay to VoE.
129      channel_delay_->extra_video_delay_ms -= diff_ms;
130      channel_delay_->extra_audio_delay_ms = base_target_delay_ms_;
131    } else {  // channel_delay_->extra_video_delay_ms > 0
132      // We have no extra video delay to remove, increase the audio delay.
133      channel_delay_->extra_audio_delay_ms += diff_ms;
134      channel_delay_->extra_video_delay_ms = base_target_delay_ms_;
135    }
136  } else {  // if (diff_ms > 0)
137    // The video delay is lower than the current audio delay.
138    // We need to decrease extra audio delay, or add extra video delay.
139    if (channel_delay_->extra_audio_delay_ms > base_target_delay_ms_) {
140      // We have extra delay in VoiceEngine.
141      // Start with decreasing the voice delay.
142      // Note: diff_ms is negative; add the negative difference.
143      channel_delay_->extra_audio_delay_ms += diff_ms;
144      channel_delay_->extra_video_delay_ms = base_target_delay_ms_;
145    } else {  // channel_delay_->extra_audio_delay_ms > base_target_delay_ms_
146      // We have no extra delay in VoiceEngine, increase the video delay.
147      // Note: diff_ms is negative; subtract the negative difference.
148      channel_delay_->extra_video_delay_ms -= diff_ms;  // X - (-Y) = X + Y.
149      channel_delay_->extra_audio_delay_ms = base_target_delay_ms_;
150    }
151  }
152
153  // Make sure that video is never below our target.
154  channel_delay_->extra_video_delay_ms = std::max(
155      channel_delay_->extra_video_delay_ms, base_target_delay_ms_);
156
157  int new_video_delay_ms;
158  if (channel_delay_->extra_video_delay_ms > base_target_delay_ms_) {
159    new_video_delay_ms = channel_delay_->extra_video_delay_ms;
160  } else {
161    // No change to the extra video delay. We are changing audio and we only
162    // allow to change one at the time.
163    new_video_delay_ms = channel_delay_->last_video_delay_ms;
164  }
165
166  // Make sure that we don't go below the extra video delay.
167  new_video_delay_ms = std::max(
168      new_video_delay_ms, channel_delay_->extra_video_delay_ms);
169
170  // Verify we don't go above the maximum allowed video delay.
171  new_video_delay_ms =
172      std::min(new_video_delay_ms, base_target_delay_ms_ + kMaxDeltaDelayMs);
173
174  int new_audio_delay_ms;
175  if (channel_delay_->extra_audio_delay_ms > base_target_delay_ms_) {
176    new_audio_delay_ms = channel_delay_->extra_audio_delay_ms;
177  } else {
178    // No change to the audio delay. We are changing video and we only
179    // allow to change one at the time.
180    new_audio_delay_ms = channel_delay_->last_audio_delay_ms;
181  }
182
183  // Make sure that we don't go below the extra audio delay.
184  new_audio_delay_ms = std::max(
185      new_audio_delay_ms, channel_delay_->extra_audio_delay_ms);
186
187  // Verify we don't go above the maximum allowed audio delay.
188  new_audio_delay_ms =
189      std::min(new_audio_delay_ms, base_target_delay_ms_ + kMaxDeltaDelayMs);
190
191  // Remember our last audio and video delays.
192  channel_delay_->last_video_delay_ms = new_video_delay_ms;
193  channel_delay_->last_audio_delay_ms = new_audio_delay_ms;
194
195  LOG(LS_VERBOSE) << "Sync video delay " << new_video_delay_ms
196                  << " and audio delay " << channel_delay_->extra_audio_delay_ms
197                  << " for video channel " << video_channel_id_
198                  << " for audio channel " << audio_channel_id_;
199
200  // Return values.
201  *total_video_delay_target_ms = new_video_delay_ms;
202  *total_audio_delay_target_ms = new_audio_delay_ms;
203  return true;
204}
205
206void StreamSynchronization::SetTargetBufferingDelay(int target_delay_ms) {
207  // Initial extra delay for audio (accounting for existing extra delay).
208  channel_delay_->extra_audio_delay_ms +=
209      target_delay_ms - base_target_delay_ms_;
210  channel_delay_->last_audio_delay_ms +=
211      target_delay_ms - base_target_delay_ms_;
212
213  // The video delay is compared to the last value (and how much we can update
214  // is limited by that as well).
215  channel_delay_->last_video_delay_ms +=
216      target_delay_ms - base_target_delay_ms_;
217
218  channel_delay_->extra_video_delay_ms +=
219      target_delay_ms - base_target_delay_ms_;
220
221  // Video is already delayed by the desired amount.
222  base_target_delay_ms_ = target_delay_ms;
223}
224
225}  // namespace webrtc
226