Logic for finding frame references moved from PacketBuffer to new class

webrtc/modules/video_coding/rtp_frame_reference_finder.cc

 /*
  *  Copyright (c) 2016 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 "webrtc/modules/video_coding/packet_buffer.h"
+#include "webrtc/modules/video_coding/rtp_frame_reference_finder.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/modules/video_coding/frame_object.h"
+#include "webrtc/modules/video_coding/packet_buffer.h"
 
 namespace webrtc {
 namespace video_coding {
 
-PacketBuffer::PacketBuffer(size_t start_buffer_size,
-                           size_t max_buffer_size,
-                           OnCompleteFrameCallback* frame_callback)
-    : size_(start_buffer_size),
-      max_size_(max_buffer_size),
-      first_seq_num_(0),
-      last_seq_num_(0),
-      first_packet_received_(false),
-      data_buffer_(start_buffer_size),
-      sequence_buffer_(start_buffer_size),
-      frame_callback_(frame_callback),
-      last_picture_id_(-1),
+RtpFrameReferenceFinder::RtpFrameReferenceFinder(
+    OnCompleteFrameCallback* frame_callback)
+    : last_picture_id_(-1),
       last_unwrap_(-1),
-      current_ss_idx_(0) {
-  RTC_DCHECK_LE(start_buffer_size, max_buffer_size);
-  // Buffer size must always be a power of 2.
-  RTC_DCHECK((start_buffer_size & (start_buffer_size - 1)) == 0);
-  RTC_DCHECK((max_buffer_size & (max_buffer_size - 1)) == 0);
-}
+      current_ss_idx_(0),

[terelius, 2016/05/09 16:39:18]

Is ss_idx an established name, or could we find something more descriptive?

[philipel, 2016/05/11 09:40:32]

Kind of, it is not as established as a GOF or GOP but it is used in the Vp9 Rtp
specification.

+      frame_callback_(frame_callback) {}
 
-bool PacketBuffer::InsertPacket(const VCMPacket& packet) {
+void RtpFrameReferenceFinder::ManageFrame(
+    std::unique_ptr<RtpFrameObject> frame) {
   rtc::CritScope lock(&crit_);
-  uint16_t seq_num = packet.seqNum;
-  size_t index = seq_num % size_;
-
-  if (!first_packet_received_) {
-    first_seq_num_ = seq_num - 1;
-    last_seq_num_ = seq_num;
-    first_packet_received_ = true;
-  }
-
-  if (sequence_buffer_[index].used) {
-    // Duplicate packet, do nothing.
-    if (data_buffer_[index].seqNum == packet.seqNum)
-      return true;
-
-    // The packet buffer is full, try to expand the buffer.
-    while (ExpandBufferSize() && sequence_buffer_[seq_num % size_].used) {
-    }
-    index = seq_num % size_;
-
-    // Packet buffer is still full.
-    if (sequence_buffer_[index].used)
-      return false;
-  }
-
-  if (AheadOf(seq_num, last_seq_num_))
-    last_seq_num_ = seq_num;
-
-  sequence_buffer_[index].frame_begin = packet.isFirstPacket;
-  sequence_buffer_[index].frame_end = packet.markerBit;
-  sequence_buffer_[index].seq_num = packet.seqNum;
-  sequence_buffer_[index].continuous = false;
-  sequence_buffer_[index].frame_created = false;
-  sequence_buffer_[index].used = true;
-  data_buffer_[index] = packet;
-
-  FindFrames(seq_num);
-  return true;
-}
-
-void PacketBuffer::ClearTo(uint16_t seq_num) {
-  rtc::CritScope lock(&crit_);
-  size_t index = first_seq_num_ % size_;
-  while (AheadOf<uint16_t>(seq_num, first_seq_num_ + 1)) {
-    index = (index + 1) % size_;
-    first_seq_num_ = Add<1 << 16>(first_seq_num_, 1);
-    sequence_buffer_[index].used = false;
-  }
-}
-
-bool PacketBuffer::ExpandBufferSize() {
-  if (size_ == max_size_)
-    return false;
-
-  size_t new_size = std::min(max_size_, 2 * size_);
-  std::vector<VCMPacket> new_data_buffer(new_size);
-  std::vector<ContinuityInfo> new_sequence_buffer(new_size);
-  for (size_t i = 0; i < size_; ++i) {
-    if (sequence_buffer_[i].used) {
-      size_t index = sequence_buffer_[i].seq_num % new_size;
-      new_sequence_buffer[index] = sequence_buffer_[i];
-      new_data_buffer[index] = data_buffer_[i];
-    }
-  }
-  size_ = new_size;
-  sequence_buffer_ = std::move(new_sequence_buffer);
-  data_buffer_ = std::move(new_data_buffer);
-  return true;
-}
-
-bool PacketBuffer::IsContinuous(uint16_t seq_num) const {
-  size_t index = seq_num % size_;
-  int prev_index = index > 0 ? index - 1 : size_ - 1;
-
-  if (!sequence_buffer_[index].used)
-    return false;
-  if (sequence_buffer_[index].frame_created)
-    return false;
-  if (sequence_buffer_[index].frame_begin)
-    return true;
-  if (!sequence_buffer_[prev_index].used)
-    return false;
-  if (sequence_buffer_[prev_index].seq_num !=
-      static_cast<uint16_t>(seq_num - 1))
-    return false;
-  if (sequence_buffer_[prev_index].continuous)
-    return true;
-
-  return false;
-}
-
-void PacketBuffer::FindFrames(uint16_t seq_num) {
-  size_t index = seq_num % size_;
-  while (IsContinuous(seq_num)) {
-    sequence_buffer_[index].continuous = true;
-
-    // If all packets of the frame is continuous, find the first packet of the
-    // frame and create an RtpFrameObject.
-    if (sequence_buffer_[index].frame_end) {
-      int start_index = index;
-      uint16_t start_seq_num = seq_num;
-
-      while (!sequence_buffer_[start_index].frame_begin) {
-        sequence_buffer_[start_index].frame_created = true;
-        start_index = start_index > 0 ? start_index - 1 : size_ - 1;
-        start_seq_num--;
-      }
-      sequence_buffer_[start_index].frame_created = true;
-
-      std::unique_ptr<RtpFrameObject> frame(
-          new RtpFrameObject(this, start_seq_num, seq_num));
-      ManageFrame(std::move(frame));
-    }
-
-    index = (index + 1) % size_;
-    ++seq_num;
-  }
-}
-
-void PacketBuffer::ReturnFrame(RtpFrameObject* frame) {
-  rtc::CritScope lock(&crit_);
-  size_t index = frame->first_seq_num() % size_;
-  size_t end = (frame->last_seq_num() + 1) % size_;
-  uint16_t seq_num = frame->first_seq_num();
-  while (index != end) {
-    if (sequence_buffer_[index].seq_num == seq_num)
-      sequence_buffer_[index].used = false;
-
-    index = (index + 1) % size_;
-    ++seq_num;
-  }
-
-  index = first_seq_num_ % size_;
-  while (AheadOf<uint16_t>(last_seq_num_, first_seq_num_) &&
-         !sequence_buffer_[index].used) {
-    ++first_seq_num_;
-    index = (index + 1) % size_;
-  }
-}
-
-bool PacketBuffer::GetBitstream(const RtpFrameObject& frame,
-                                uint8_t* destination) {
-  rtc::CritScope lock(&crit_);
-
-  size_t index = frame.first_seq_num() % size_;
-  size_t end = (frame.last_seq_num() + 1) % size_;
-  uint16_t seq_num = frame.first_seq_num();
-  while (index != end) {
-    if (!sequence_buffer_[index].used ||
-        sequence_buffer_[index].seq_num != seq_num) {
-      return false;
-    }
-
-    const uint8_t* source = data_buffer_[index].dataPtr;
-    size_t length = data_buffer_[index].sizeBytes;
-    memcpy(destination, source, length);
-    destination += length;
-    index = (index + 1) % size_;
-    ++seq_num;
-  }
-  return true;
-}
-
-void PacketBuffer::ManageFrame(std::unique_ptr<RtpFrameObject> frame) {
-  size_t start_index = frame->first_seq_num() % size_;
-  VideoCodecType codec_type = data_buffer_[start_index].codec;
-
-  switch (codec_type) {
+  switch (frame->codec_type()) {
     case kVideoCodecULPFEC:
     case kVideoCodecRED:
     case kVideoCodecUnknown:
       RTC_NOTREACHED();
       break;
     case kVideoCodecVP8:
       ManageFrameVp8(std::move(frame));
       break;
     case kVideoCodecVP9:
       ManageFrameVp9(std::move(frame));
       break;
     case kVideoCodecH264:
     case kVideoCodecI420:
     case kVideoCodecGeneric:
       ManageFrameGeneric(std::move(frame));
       break;
   }
 }
 
-void PacketBuffer::RetryStashedFrames() {
+void RtpFrameReferenceFinder::RetryStashedFrames() {
   size_t num_stashed_frames = stashed_frames_.size();
 
   // Clean up stashed frames if there are too many.
   while (stashed_frames_.size() > kMaxStashedFrames)
     stashed_frames_.pop();
 
   // Since frames are stashed if there is not enough data to determine their
   // frame references we should at most check |stashed_frames_.size()| in
   // order to not pop and push frames in and endless loop.
   for (size_t i = 0; i < num_stashed_frames && !stashed_frames_.empty(); ++i) {
     std::unique_ptr<RtpFrameObject> frame = std::move(stashed_frames_.front());
     stashed_frames_.pop();
     ManageFrame(std::move(frame));
   }
 }
 
-void PacketBuffer::ManageFrameGeneric(
+void RtpFrameReferenceFinder::ManageFrameGeneric(
     std::unique_ptr<RtpFrameObject> frame) {
-  size_t index = frame->first_seq_num() % size_;
-  const VCMPacket& packet = data_buffer_[index];
-
-  if (packet.frameType == kVideoFrameKey)
+  if (frame->frame_type() == kVideoFrameKey)
     last_seq_num_gop_[frame->last_seq_num()] = frame->last_seq_num();
 
   // We have received a frame but not yet a keyframe, stash this frame.
   if (last_seq_num_gop_.empty()) {
     stashed_frames_.emplace(std::move(frame));
     return;
   }
 
   // Clean up info for old keyframes but make sure to keep info
   // for the last keyframe.
   auto clean_to = last_seq_num_gop_.lower_bound(frame->last_seq_num() - 100);
   if (clean_to != last_seq_num_gop_.end())
     last_seq_num_gop_.erase(last_seq_num_gop_.begin(), clean_to);
 
   // Find the last sequence number of the last frame for the keyframe
   // that this frame indirectly references.
   auto seq_num_it = last_seq_num_gop_.upper_bound(frame->last_seq_num());
   seq_num_it--;
 
   // Make sure the packet sequence numbers are continuous, otherwise stash
   // this frame.
-  if (packet.frameType == kVideoFrameDelta) {
+  if (frame->frame_type() == kVideoFrameDelta) {
     if (seq_num_it->second !=
         static_cast<uint16_t>(frame->first_seq_num() - 1)) {
       stashed_frames_.emplace(std::move(frame));
       return;
     }
   }
 
   RTC_DCHECK(AheadOrAt(frame->last_seq_num(), seq_num_it->first));
 
-  // Since keyframes can cause reordering of the frames delivered from
-  // FindFrames() we can't simply assign the picture id according to some
-  // incrementing counter.
+  // Since keyframes can cause reordering we can't simply assign the
+  // picture id according to some incrementing counter.
   frame->picture_id = frame->last_seq_num();
-  frame->num_references = packet.frameType == kVideoFrameDelta;
+  frame->num_references = frame->frame_type() == kVideoFrameDelta;
   frame->references[0] = seq_num_it->second;
   seq_num_it->second = frame->picture_id;
 
   last_picture_id_ = frame->picture_id;
   frame_callback_->OnCompleteFrame(std::move(frame));
   RetryStashedFrames();
 }
 
-void PacketBuffer::ManageFrameVp8(std::unique_ptr<RtpFrameObject> frame) {
-  size_t index = frame->first_seq_num() % size_;
-  const VCMPacket& packet = data_buffer_[index];
-  const RTPVideoHeaderVP8& codec_header =
-      packet.codecSpecificHeader.codecHeader.VP8;
+void RtpFrameReferenceFinder::ManageFrameVp8(
+    std::unique_ptr<RtpFrameObject> frame) {
+  RTPVideoTypeHeader* rtp_codec_header = frame->GetCodecHeader();
+  if (!rtp_codec_header)
+    return;
+
+  const RTPVideoHeaderVP8& codec_header = rtp_codec_header->VP8;
 
   if (codec_header.pictureId == kNoPictureId ||
       codec_header.temporalIdx == kNoTemporalIdx ||
       codec_header.tl0PicIdx == kNoTl0PicIdx) {
     ManageFrameGeneric(std::move(frame));
     return;
   }
 
   frame->picture_id = codec_header.pictureId % kPicIdLength;
 
@@ skipping 12 matching lines @@
       last_picture_id_ = Add<kPicIdLength>(last_picture_id_, 1);
     }
   }
 
   // Clean up info for base layers that are too old.
   uint8_t old_tl0_pic_idx = codec_header.tl0PicIdx - kMaxLayerInfo;
   auto clean_layer_info_to = layer_info_.lower_bound(old_tl0_pic_idx);
   layer_info_.erase(layer_info_.begin(), clean_layer_info_to);
 
   // Clean up info about not yet received frames that are too old.
-  uint16_t old_picture_id = Subtract<kPicIdLength>(frame->picture_id,
-                                                   kMaxNotYetReceivedFrames);
+  uint16_t old_picture_id =
+      Subtract<kPicIdLength>(frame->picture_id, kMaxNotYetReceivedFrames);
   auto clean_frames_to = not_yet_received_frames_.lower_bound(old_picture_id);
   not_yet_received_frames_.erase(not_yet_received_frames_.begin(),
                                  clean_frames_to);
 
-  if (packet.frameType == kVideoFrameKey) {
+  if (frame->frame_type() == kVideoFrameKey) {
     frame->num_references = 0;
     layer_info_[codec_header.tl0PicIdx].fill(-1);
     CompletedFrameVp8(std::move(frame));
     return;
   }
 
   auto layer_info_it = layer_info_.find(codec_header.temporalIdx == 0
                                             ? codec_header.tl0PicIdx - 1
                                             : codec_header.tl0PicIdx);
 
@@ skipping 27 matching lines @@
   }
 
   // Find all references for this frame.
   frame->num_references = 0;
   for (uint8_t layer = 0; layer <= codec_header.temporalIdx; ++layer) {
     RTC_DCHECK_NE(-1, layer_info_it->second[layer]);
 
     // If we have not yet received a frame between this frame and the referenced
     // frame then we have to wait for that frame to be completed first.
     auto not_received_frame_it =
-             not_yet_received_frames_.upper_bound(layer_info_it->second[layer]);
+        not_yet_received_frames_.upper_bound(layer_info_it->second[layer]);
     if (not_received_frame_it != not_yet_received_frames_.end() &&
         AheadOf<uint16_t, kPicIdLength>(frame->picture_id,
                                         *not_received_frame_it)) {
       stashed_frames_.emplace(std::move(frame));
       return;
     }
 
     ++frame->num_references;
     frame->references[layer] = layer_info_it->second[layer];
   }
 
   CompletedFrameVp8(std::move(frame));
 }
 
-void PacketBuffer::CompletedFrameVp8(std::unique_ptr<RtpFrameObject> frame) {
-  size_t index = frame->first_seq_num() % size_;
-  const VCMPacket& packet = data_buffer_[index];
-  const RTPVideoHeaderVP8& codec_header =
-      packet.codecSpecificHeader.codecHeader.VP8;
+void RtpFrameReferenceFinder::CompletedFrameVp8(
+    std::unique_ptr<RtpFrameObject> frame) {
+  RTPVideoTypeHeader* rtp_codec_header = frame->GetCodecHeader();
+  if (!rtp_codec_header)
+    return;
+
+  const RTPVideoHeaderVP8& codec_header = rtp_codec_header->VP8;
 
   uint8_t tl0_pic_idx = codec_header.tl0PicIdx;
   uint8_t temporal_index = codec_header.temporalIdx;
   auto layer_info_it = layer_info_.find(tl0_pic_idx);
 
   // Update this layer info and newer.
   while (layer_info_it != layer_info_.end()) {
     if (layer_info_it->second[temporal_index] != -1 &&
         AheadOf<uint16_t, kPicIdLength>(layer_info_it->second[temporal_index],
                                         frame->picture_id)) {
       // The frame was not newer, then no subsequent layer info have to be
       // update.
       break;
     }
 
     layer_info_it->second[codec_header.temporalIdx] = frame->picture_id;
     ++tl0_pic_idx;
     layer_info_it = layer_info_.find(tl0_pic_idx);
   }
   not_yet_received_frames_.erase(frame->picture_id);
 
   for (size_t i = 0; i < frame->num_references; ++i)
     frame->references[i] = UnwrapPictureId(frame->references[i]);
   frame->picture_id = UnwrapPictureId(frame->picture_id);
 
   frame_callback_->OnCompleteFrame(std::move(frame));
   RetryStashedFrames();
 }
 
-void PacketBuffer::ManageFrameVp9(std::unique_ptr<RtpFrameObject> frame) {
-  size_t index = frame->first_seq_num() % size_;
-  const VCMPacket& packet = data_buffer_[index];
-  const RTPVideoHeaderVP9& codec_header =
-      packet.codecSpecificHeader.codecHeader.VP9;
+void RtpFrameReferenceFinder::ManageFrameVp9(
+    std::unique_ptr<RtpFrameObject> frame) {
+  RTPVideoTypeHeader* rtp_codec_header = frame->GetCodecHeader();
+  if (!rtp_codec_header)
+    return;
+
+  const RTPVideoHeaderVP9& codec_header = rtp_codec_header->VP9;
 
   if (codec_header.picture_id == kNoPictureId) {
     ManageFrameGeneric(std::move(frame));
     return;
   }
 
   frame->spatial_layer = codec_header.spatial_idx;
   frame->inter_layer_predicted = codec_header.inter_layer_predicted;
   frame->picture_id = codec_header.picture_id % kPicIdLength;
 
@@ skipping 28 matching lines @@
           frame->picture_id, &scalability_structures_[current_ss_idx_]);
       gof_info_.insert(std::make_pair(codec_header.tl0_pic_idx, pid_and_gof));
     }
   }
 
   // Clean up info for base layers that are too old.
   uint8_t old_tl0_pic_idx = codec_header.tl0_pic_idx - kMaxGofSaved;
   auto clean_gof_info_to = gof_info_.lower_bound(old_tl0_pic_idx);
   gof_info_.erase(gof_info_.begin(), clean_gof_info_to);
 
-  if (packet.frameType == kVideoFrameKey) {
+  if (frame->frame_type() == kVideoFrameKey) {
     // When using GOF all keyframes must include the scalability structure.
     if (!codec_header.ss_data_available)
       LOG(LS_WARNING) << "Received keyframe without scalability structure";
 
     frame->num_references = 0;
     GofInfoVP9* gof = gof_info_.find(codec_header.tl0_pic_idx)->second.second;
     FrameReceivedVp9(frame->picture_id, *gof);
     CompletedFrameVp9(std::move(frame));
     return;
   }
@@ skipping 57 matching lines @@
     // then ignore this reference.
     if (UpSwitchInIntervalVp9(frame->picture_id, codec_header.temporal_idx,
                               frame->references[i])) {
       --frame->num_references;
     }
   }
 
   CompletedFrameVp9(std::move(frame));
 }
 
-bool PacketBuffer::MissingRequiredFrameVp9(uint16_t picture_id,
-                                           const GofInfoVP9& gof) {
+bool RtpFrameReferenceFinder::MissingRequiredFrameVp9(uint16_t picture_id,
+                                                      const GofInfoVP9& gof) {
   size_t diff = ForwardDiff<uint16_t, kPicIdLength>(gof.pid_start, picture_id);
   size_t gof_idx = diff % gof.num_frames_in_gof;
   size_t temporal_idx = gof.temporal_idx[gof_idx];
 
   // For every reference this frame has, check if there is a frame missing in
   // the interval (|ref_pid|, |picture_id|) in any of the lower temporal
   // layers. If so, we are missing a required frame.
   uint8_t num_references = gof.num_ref_pics[gof_idx];
   for (size_t i = 0; i < num_references; ++i) {
     uint16_t ref_pid =
         Subtract<kPicIdLength>(picture_id, gof.pid_diff[gof_idx][i]);
     for (size_t l = 0; l < temporal_idx; ++l) {
       auto missing_frame_it = missing_frames_for_layer_[l].lower_bound(ref_pid);
       if (missing_frame_it != missing_frames_for_layer_[l].end() &&
           AheadOf<uint16_t, kPicIdLength>(picture_id, *missing_frame_it)) {
         return true;
       }
     }
   }
   return false;
 }
 
-void PacketBuffer::FrameReceivedVp9(uint16_t picture_id,
-                                    const GofInfoVP9& gof) {
+void RtpFrameReferenceFinder::FrameReceivedVp9(uint16_t picture_id,
+                                               const GofInfoVP9& gof) {
   RTC_DCHECK_NE(-1, last_picture_id_);
 
   // If there is a gap, find which temporal layer the missing frames
   // belong to and add the frame as missing for that temporal layer.
   // Otherwise, remove this frame from the set of missing frames.
   if (AheadOf<uint16_t, kPicIdLength>(picture_id, last_picture_id_)) {
     size_t diff =
         ForwardDiff<uint16_t, kPicIdLength>(gof.pid_start, last_picture_id_);
     size_t gof_idx = diff % gof.num_frames_in_gof;
 
     last_picture_id_ = Add<kPicIdLength>(last_picture_id_, 1);
     while (last_picture_id_ != picture_id) {
       ++gof_idx;
       RTC_DCHECK_NE(0ul, gof_idx % gof.num_frames_in_gof);
       size_t temporal_idx = gof.temporal_idx[gof_idx];
       missing_frames_for_layer_[temporal_idx].insert(last_picture_id_);
       last_picture_id_ = Add<kPicIdLength>(last_picture_id_, 1);
     }
   } else {
     size_t diff =
         ForwardDiff<uint16_t, kPicIdLength>(gof.pid_start, picture_id);
     size_t gof_idx = diff % gof.num_frames_in_gof;
     size_t temporal_idx = gof.temporal_idx[gof_idx];
     missing_frames_for_layer_[temporal_idx].erase(picture_id);
   }
 }
 
-bool PacketBuffer::UpSwitchInIntervalVp9(uint16_t picture_id,
-                                         uint8_t temporal_idx,
-                                         uint16_t pid_ref) {
+bool RtpFrameReferenceFinder::UpSwitchInIntervalVp9(uint16_t picture_id,
+                                                    uint8_t temporal_idx,
+                                                    uint16_t pid_ref) {
   for (auto up_switch_it = up_switch_.upper_bound(pid_ref);
        up_switch_it != up_switch_.end() &&
        AheadOf<uint16_t, kPicIdLength>(picture_id, up_switch_it->first);
        ++up_switch_it) {
     if (up_switch_it->second < temporal_idx)
       return true;
   }
 
   return false;
 }
 
-void PacketBuffer::CompletedFrameVp9(std::unique_ptr<RtpFrameObject> frame) {
+void RtpFrameReferenceFinder::CompletedFrameVp9(
+    std::unique_ptr<RtpFrameObject> frame) {
   for (size_t i = 0; i < frame->num_references; ++i)
     frame->references[i] = UnwrapPictureId(frame->references[i]);
   frame->picture_id = UnwrapPictureId(frame->picture_id);
 
   frame_callback_->OnCompleteFrame(std::move(frame));
   RetryStashedFrames();
 }
 
-uint16_t PacketBuffer::UnwrapPictureId(uint16_t picture_id) {
+uint16_t RtpFrameReferenceFinder::UnwrapPictureId(uint16_t picture_id) {
   RTC_DCHECK_NE(-1, last_unwrap_);
 
   uint16_t unwrap_truncated = last_unwrap_ % kPicIdLength;
   uint16_t diff = MinDiff<uint16_t, kPicIdLength>(unwrap_truncated, picture_id);
 
   if (AheadOf<uint16_t, kPicIdLength>(picture_id, unwrap_truncated))
     last_unwrap_ = Add<1 << 16>(last_unwrap_, diff);
   else
     last_unwrap_ = Subtract<1 << 16>(last_unwrap_, diff);
 
   return last_unwrap_;
 }
 
-void PacketBuffer::Flush() {
-  rtc::CritScope lock(&crit_);
-  for (size_t i = 0; i < size_; ++i)
-    sequence_buffer_[i].used = false;
-
-  last_seq_num_gop_.clear();
-  while (!stashed_frames_.empty())
-    stashed_frames_.pop();
-  not_yet_received_frames_.clear();
-
-  first_packet_received_ = false;
-}
-
 }  // namespace video_coding
 }  // namespace webrtc