diff --git a/modules/video_coding/BUILD.gn b/modules/video_coding/BUILD.gn
index a3187c2..96b48b6 100644
--- a/modules/video_coding/BUILD.gn
+++ b/modules/video_coding/BUILD.gn
@@ -970,6 +970,7 @@
       "session_info_unittest.cc",
       "test/stream_generator.cc",
       "test/stream_generator.h",
+      "timestamp_map_unittest.cc",
       "timing_unittest.cc",
       "unique_timestamp_counter_unittest.cc",
       "utility/decoded_frames_history_unittest.cc",
diff --git a/modules/video_coding/generic_decoder.cc b/modules/video_coding/generic_decoder.cc
index 85c68da..621fd73 100644
--- a/modules/video_coding/generic_decoder.cc
+++ b/modules/video_coding/generic_decoder.cc
@@ -93,16 +93,27 @@
   // callbacks from one call to Decode().
   absl::optional<VCMFrameInformation> frameInfo;
   int timestamp_map_size = 0;
+  int dropped_frames = 0;
   {
     MutexLock lock(&lock_);
+    int initial_timestamp_map_size = _timestampMap.Size();
     frameInfo = _timestampMap.Pop(decodedImage.timestamp());
     timestamp_map_size = _timestampMap.Size();
+    // _timestampMap.Pop() erases all frame upto the specified timestamp and
+    // return the frame info for this timestamp if it exists. Thus, the
+    // difference in the _timestampMap size before and after Pop() will show
+    // internally dropped frames.
+    dropped_frames =
+        initial_timestamp_map_size - timestamp_map_size - (frameInfo ? 1 : 0);
+  }
+
+  if (dropped_frames > 0) {
+    _receiveCallback->OnDroppedFrames(dropped_frames);
   }
 
   if (!frameInfo) {
     RTC_LOG(LS_WARNING) << "Too many frames backed up in the decoder, dropping "
                            "this one.";
-    _receiveCallback->OnDroppedFrames(1);
     return;
   }
 
@@ -197,17 +208,29 @@
 
 void VCMDecodedFrameCallback::Map(uint32_t timestamp,
                                   const VCMFrameInformation& frameInfo) {
-  MutexLock lock(&lock_);
-  _timestampMap.Add(timestamp, frameInfo);
+  int dropped_frames = 0;
+  {
+    MutexLock lock(&lock_);
+    int initial_size = _timestampMap.Size();
+    _timestampMap.Add(timestamp, frameInfo);
+    // If no frame is dropped, the new size should be |initial_size| + 1
+    dropped_frames = (initial_size + 1) - _timestampMap.Size();
+  }
+  if (dropped_frames > 0) {
+    _receiveCallback->OnDroppedFrames(dropped_frames);
+  }
 }
 
-int32_t VCMDecodedFrameCallback::Pop(uint32_t timestamp) {
-  MutexLock lock(&lock_);
-  if (_timestampMap.Pop(timestamp) == absl::nullopt) {
-    return VCM_GENERAL_ERROR;
+void VCMDecodedFrameCallback::ClearTimestampMap() {
+  int dropped_frames = 0;
+  {
+    MutexLock lock(&lock_);
+    dropped_frames = _timestampMap.Size();
+    _timestampMap.Clear();
   }
-  _receiveCallback->OnDroppedFrames(1);
-  return VCM_OK;
+  if (dropped_frames > 0) {
+    _receiveCallback->OnDroppedFrames(dropped_frames);
+  }
 }
 
 VCMGenericDecoder::VCMGenericDecoder(std::unique_ptr<VideoDecoder> decoder)
@@ -281,11 +304,10 @@
   if (ret < WEBRTC_VIDEO_CODEC_OK) {
     RTC_LOG(LS_WARNING) << "Failed to decode frame with timestamp "
                         << frame.Timestamp() << ", error code: " << ret;
-    _callback->Pop(frame.Timestamp());
-    return ret;
+    _callback->ClearTimestampMap();
   } else if (ret == WEBRTC_VIDEO_CODEC_NO_OUTPUT) {
-    // No output
-    _callback->Pop(frame.Timestamp());
+    // No output.
+    _callback->ClearTimestampMap();
   }
   return ret;
 }
diff --git a/modules/video_coding/generic_decoder.h b/modules/video_coding/generic_decoder.h
index 2ff6b20..8e79cb4 100644
--- a/modules/video_coding/generic_decoder.h
+++ b/modules/video_coding/generic_decoder.h
@@ -45,7 +45,7 @@
   void OnDecoderImplementationName(const char* implementation_name);
 
   void Map(uint32_t timestamp, const VCMFrameInformation& frameInfo);
-  int32_t Pop(uint32_t timestamp);
+  void ClearTimestampMap();
 
  private:
   SequenceChecker construction_thread_;
@@ -104,7 +104,6 @@
 
  private:
   VCMDecodedFrameCallback* _callback;
-  VCMFrameInformation _frameInfos[kDecoderFrameMemoryLength];
   std::unique_ptr<VideoDecoder> decoder_;
   VideoCodecType _codecType;
   const bool _isExternal;
diff --git a/modules/video_coding/timestamp_map.cc b/modules/video_coding/timestamp_map.cc
index 7762e36..f6fb818 100644
--- a/modules/video_coding/timestamp_map.cc
+++ b/modules/video_coding/timestamp_map.cc
@@ -69,4 +69,11 @@
              : next_add_idx_ + capacity_ - next_pop_idx_;
 }
 
+void VCMTimestampMap::Clear() {
+  while (!IsEmpty()) {
+    ring_buffer_[next_pop_idx_].timestamp = 0;
+    next_pop_idx_ = (next_pop_idx_ + 1) % capacity_;
+  }
+}
+
 }  // namespace webrtc
diff --git a/modules/video_coding/timestamp_map.h b/modules/video_coding/timestamp_map.h
index 86ce55b..dc20a05 100644
--- a/modules/video_coding/timestamp_map.h
+++ b/modules/video_coding/timestamp_map.h
@@ -43,6 +43,7 @@
   void Add(uint32_t timestamp, const VCMFrameInformation& data);
   absl::optional<VCMFrameInformation> Pop(uint32_t timestamp);
   size_t Size() const;
+  void Clear();
 
  private:
   struct TimestampDataTuple {
diff --git a/modules/video_coding/timestamp_map_unittest.cc b/modules/video_coding/timestamp_map_unittest.cc
new file mode 100644
index 0000000..5e90786
--- /dev/null
+++ b/modules/video_coding/timestamp_map_unittest.cc
@@ -0,0 +1,121 @@
+/*
+ *  Copyright (c) 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 "modules/video_coding/timestamp_map.h"
+
+#include "test/gmock.h"
+#include "test/gtest.h"
+
+namespace webrtc {
+namespace video_coding {
+namespace {
+constexpr int kTimestampMapSize = 6;
+constexpr int kTimestamp1 = 1;
+constexpr int kTimestamp2 = 2;
+constexpr int kNoExistingTimestamp3 = 3;
+constexpr int kTimestamp4 = 4;
+constexpr int kTimestamp5 = 5;
+constexpr int kTimestamp6 = 6;
+constexpr int kTimestamp7 = 7;
+constexpr int64_t kRenderTime1 = 1000;
+constexpr int64_t kRenderTime2 = 2000;
+constexpr int64_t kRenderTime4 = 4000;
+constexpr int64_t kRenderTime5 = 5000;
+constexpr int64_t kRenderTime6 = 6000;
+constexpr int64_t kRenderTime7 = 7000;
+}  // namespace
+
+class VcmTimestampMapTest : public ::testing::Test {
+ protected:
+  VcmTimestampMapTest() : _timestampMap(kTimestampMapSize) {}
+
+  void SetUp() override {
+    _timestampMap.Add(kTimestamp1, VCMFrameInformation({kRenderTime1}));
+    _timestampMap.Add(kTimestamp2, VCMFrameInformation({kRenderTime2}));
+    _timestampMap.Add(kTimestamp4, VCMFrameInformation({kRenderTime4}));
+  }
+
+  VCMTimestampMap _timestampMap;
+};
+
+TEST_F(VcmTimestampMapTest, PopExistingFrameInfo) {
+  EXPECT_EQ(_timestampMap.Size(), 3u);
+  auto frameInfo = _timestampMap.Pop(kTimestamp1);
+  ASSERT_TRUE(frameInfo);
+  EXPECT_EQ(frameInfo->renderTimeMs, kRenderTime1);
+  frameInfo = _timestampMap.Pop(kTimestamp2);
+  ASSERT_TRUE(frameInfo);
+  EXPECT_EQ(frameInfo->renderTimeMs, kRenderTime2);
+  frameInfo = _timestampMap.Pop(kTimestamp4);
+  ASSERT_TRUE(frameInfo);
+  EXPECT_EQ(frameInfo->renderTimeMs, kRenderTime4);
+}
+
+TEST_F(VcmTimestampMapTest, PopNonexistingClearsOlderFrameInfos) {
+  auto frameInfo = _timestampMap.Pop(kNoExistingTimestamp3);
+  EXPECT_FALSE(frameInfo);
+  EXPECT_EQ(_timestampMap.Size(), 1u);
+}
+
+TEST_F(VcmTimestampMapTest, SizeIsIncrementedWhenAddingNewFrameInfo) {
+  EXPECT_EQ(_timestampMap.Size(), 3u);
+  _timestampMap.Add(kTimestamp5, VCMFrameInformation({kRenderTime5}));
+  EXPECT_EQ(_timestampMap.Size(), 4u);
+  _timestampMap.Add(kTimestamp6, VCMFrameInformation({kRenderTime6}));
+  EXPECT_EQ(_timestampMap.Size(), 5u);
+}
+
+TEST_F(VcmTimestampMapTest, SizeIsDecreasedWhenPoppingFrameInfo) {
+  EXPECT_EQ(_timestampMap.Size(), 3u);
+  EXPECT_TRUE(_timestampMap.Pop(kTimestamp1));
+  EXPECT_EQ(_timestampMap.Size(), 2u);
+  EXPECT_TRUE(_timestampMap.Pop(kTimestamp2));
+  EXPECT_EQ(_timestampMap.Size(), 1u);
+  EXPECT_FALSE(_timestampMap.Pop(kNoExistingTimestamp3));
+  EXPECT_EQ(_timestampMap.Size(), 1u);
+  EXPECT_TRUE(_timestampMap.Pop(kTimestamp4));
+  EXPECT_EQ(_timestampMap.Size(), 0u);
+}
+
+TEST_F(VcmTimestampMapTest, ClearEmptiesMap) {
+  EXPECT_EQ(_timestampMap.Size(), 3u);
+  _timestampMap.Clear();
+  EXPECT_EQ(_timestampMap.Size(), 0u);
+  // Clear empty map does nothing.
+  _timestampMap.Clear();
+  EXPECT_EQ(_timestampMap.Size(), 0u);
+}
+
+TEST_F(VcmTimestampMapTest, PopLastAddedClearsMap) {
+  EXPECT_EQ(_timestampMap.Size(), 3u);
+  EXPECT_TRUE(_timestampMap.Pop(kTimestamp4));
+  EXPECT_EQ(_timestampMap.Size(), 0u);
+}
+
+TEST_F(VcmTimestampMapTest, LastAddedIsDiscardedIfMapGetsFull) {
+  EXPECT_EQ(_timestampMap.Size(), 3u);
+  _timestampMap.Add(kTimestamp5, VCMFrameInformation({kRenderTime5}));
+  EXPECT_EQ(_timestampMap.Size(), 4u);
+  _timestampMap.Add(kTimestamp6, VCMFrameInformation({kRenderTime6}));
+  EXPECT_EQ(_timestampMap.Size(), 5u);
+  _timestampMap.Add(kTimestamp7, VCMFrameInformation({kRenderTime7}));
+  // Size is not incremented since the oldest element is discarded.
+  EXPECT_EQ(_timestampMap.Size(), 5u);
+  EXPECT_FALSE(_timestampMap.Pop(kTimestamp1));
+  EXPECT_TRUE(_timestampMap.Pop(kTimestamp2));
+  EXPECT_TRUE(_timestampMap.Pop(kTimestamp4));
+  EXPECT_TRUE(_timestampMap.Pop(kTimestamp5));
+  EXPECT_TRUE(_timestampMap.Pop(kTimestamp6));
+  EXPECT_TRUE(_timestampMap.Pop(kTimestamp7));
+  EXPECT_EQ(_timestampMap.Size(), 0u);
+}
+
+}  // namespace video_coding
+}  // namespace webrtc