From 20317f9ca48fa3376e5356bf3e951d61da7a14f0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=85sa=20Persson?= <asapersson@webrtc.org>
Date: Wed, 15 Aug 2018 08:57:54 +0200
Subject: [PATCH] Clear encoded frame map on gap in timestamp.
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Keep a small window in order to distinguish old and new timestamp.

Bug: chromium:816819
Change-Id: Iefa694c744e8e4b19d3857c567162cdc9410b4da
Reviewed-on: https://webrtc-review.googlesource.com/94141
Commit-Queue: Åsa Persson <asapersson@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Yves Gerey <yvesg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24285}
---
 video/send_statistics_proxy.cc          | 17 +++++++++++++++++
 video/send_statistics_proxy_unittest.cc |  8 ++++----
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/video/send_statistics_proxy.cc b/video/send_statistics_proxy.cc
index dac3c03dad..2fb955c3dc 100644
--- a/video/send_statistics_proxy.cc
+++ b/video/send_statistics_proxy.cc
@@ -12,12 +12,14 @@
 
 #include <algorithm>
 #include <cmath>
+#include <limits>
 #include <utility>
 
 #include "common_types.h"  // NOLINT(build/include)
 #include "modules/video_coding/include/video_codec_interface.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
+#include "rtc_base/numerics/mod_ops.h"
 #include "rtc_base/strings/string_builder.h"
 #include "system_wrappers/include/field_trial.h"
 #include "system_wrappers/include/metrics.h"
@@ -27,6 +29,7 @@ namespace {
 const float kEncodeTimeWeigthFactor = 0.5f;
 const size_t kMaxEncodedFrameMapSize = 150;
 const int64_t kMaxEncodedFrameWindowMs = 800;
+const uint32_t kMaxEncodedFrameTimestampDiff = 900000;  // 10 sec.
 const int64_t kBucketSizeMs = 100;
 const size_t kBucketCount = 10;
 
@@ -173,6 +176,9 @@ SendStatisticsProxy::UmaSamplesContainer::UmaSamplesContainer(
       num_streams_(0),
       num_pixels_highest_stream_(0) {
   InitializeBitrateCounters(stats);
+  static_assert(
+      kMaxEncodedFrameTimestampDiff < std::numeric_limits<uint32_t>::max() / 2,
+      "has to be smaller than half range");
 }
 
 SendStatisticsProxy::UmaSamplesContainer::~UmaSamplesContainer() {}
@@ -241,6 +247,17 @@ bool SendStatisticsProxy::UmaSamplesContainer::InsertEncodedFrame(
     encoded_frames_.clear();
   }
 
+  // Check for jump in timestamp.
+  if (!encoded_frames_.empty()) {
+    uint32_t oldest_timestamp = encoded_frames_.begin()->first;
+    if (ForwardDiff(oldest_timestamp, encoded_frame._timeStamp) >
+        kMaxEncodedFrameTimestampDiff) {
+      // Gap detected, clear frames to have a sequence where newest timestamp
+      // is not too far away from oldest in order to distinguish old and new.
+      encoded_frames_.clear();
+    }
+  }
+
   auto it = encoded_frames_.find(encoded_frame._timeStamp);
   if (it == encoded_frames_.end()) {
     // First frame with this timestamp.
diff --git a/video/send_statistics_proxy_unittest.cc b/video/send_statistics_proxy_unittest.cc
index f4e2fe7486..6942e36b5d 100644
--- a/video/send_statistics_proxy_unittest.cc
+++ b/video/send_statistics_proxy_unittest.cc
@@ -1027,7 +1027,7 @@ TEST_F(SendStatisticsProxyTest, InputResolutionHistogramsAreUpdated) {
 
 TEST_F(SendStatisticsProxyTest, SentResolutionHistogramsAreUpdated) {
   const int64_t kMaxEncodedFrameWindowMs = 800;
-  const int kFps = 20;
+  const int kFps = 5;
   const int kNumFramesPerWindow = kFps * kMaxEncodedFrameWindowMs / 1000;
   const int kMinSamples =  // Sample added when removed from EncodedFrameMap.
       SendStatisticsProxy::kMinRequiredMetricsSamples + kNumFramesPerWindow;
@@ -1036,7 +1036,7 @@ TEST_F(SendStatisticsProxyTest, SentResolutionHistogramsAreUpdated) {
   // Not enough samples, stats should not be updated.
   for (int i = 0; i < kMinSamples - 1; ++i) {
     fake_clock_.AdvanceTimeMilliseconds(1000 / kFps);
-    ++encoded_image._timeStamp;
+    encoded_image._timeStamp += 90 * 1000 / kFps;
     statistics_proxy_->OnSendEncodedImage(encoded_image, nullptr);
   }
   SetUp();  // Reset stats proxy also causes histograms to be reported.
@@ -1044,10 +1044,10 @@ TEST_F(SendStatisticsProxyTest, SentResolutionHistogramsAreUpdated) {
   EXPECT_EQ(0, metrics::NumSamples("WebRTC.Video.SentHeightInPixels"));
 
   // Enough samples, max resolution per frame should be reported.
-  encoded_image._timeStamp = 0xfffffff0;  // Will wrap.
+  encoded_image._timeStamp = 0xffff0000;  // Will wrap.
   for (int i = 0; i < kMinSamples; ++i) {
     fake_clock_.AdvanceTimeMilliseconds(1000 / kFps);
-    ++encoded_image._timeStamp;
+    encoded_image._timeStamp += 90 * 1000 / kFps;
     encoded_image._encodedWidth = kWidth;
     encoded_image._encodedHeight = kHeight;
     statistics_proxy_->OnSendEncodedImage(encoded_image, nullptr);