text: /*
   *  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 "modules/video_coding/rtp_frame_reference_finder.h"
  
  #include <algorithm>
  #include <limits>
  
  #include "modules/video_coding/frame_object.h"
  #include "modules/video_coding/packet_buffer.h"
  #include "rtc_base/checks.h"
  #include "rtc_base/logging.h"
  #include "rtc_base/system/fallthrough.h"
  
  namespace webrtc {
  namespace video_coding {
  
  RtpFrameReferenceFinder::RtpFrameReferenceFinder(
      OnCompleteFrameCallback* frame_callback)
      : last_picture_id_(-1),
        last_unwrap_(-1),
        current_ss_idx_(0),
        cleared_to_seq_num_(-1),
        frame_callback_(frame_callback) {}
  
  void RtpFrameReferenceFinder::ManageFrame(
      std::unique_ptr<RtpFrameObject> frame) {
    rtc::CritScope lock(&crit_);
  
    // If we have cleared past this frame, drop it.
    if (cleared_to_seq_num_ != -1 &&
        AheadOf<uint16_t>(cleared_to_seq_num_, frame->first_seq_num())) {
      return;
    }
  
    FrameDecision decision = ManageFrameInternal(frame.get());
  
    switch (decision) {
      case kStash:
        if (stashed_frames_.size() > kMaxStashedFrames)
          stashed_frames_.pop_back();
        stashed_frames_.push_front(std::move(frame));
        break;
      case kHandOff:
        frame_callback_->OnCompleteFrame(std::move(frame));
        RetryStashedFrames();
        break;
      case kDrop:
        break;
    }
  }
  
  void RtpFrameReferenceFinder::RetryStashedFrames() {
    bool complete_frame = false;
    do {
      complete_frame = false;
      for (auto frame_it = stashed_frames_.begin();
           frame_it != stashed_frames_.end();) {
        FrameDecision decision = ManageFrameInternal(frame_it->get());
  
        switch (decision) {
          case kStash:
            ++frame_it;
            break;
          case kHandOff:
            complete_frame = true;
            frame_callback_->OnCompleteFrame(std::move(*frame_it));
            RTC_FALLTHROUGH();
          case kDrop:
            frame_it = stashed_frames_.erase(frame_it);
        }
      }
    } while (complete_frame);
  }
  
  RtpFrameReferenceFinder::FrameDecision
  RtpFrameReferenceFinder::ManageFrameInternal(RtpFrameObject* frame) {
    switch (frame->codec_type()) {
      case kVideoCodecFlexfec:
      case kVideoCodecULPFEC:
      case kVideoCodecRED:
        RTC_NOTREACHED();
        break;
      case kVideoCodecVP8:
        return ManageFrameVp8(frame);
      case kVideoCodecVP9:
        return ManageFrameVp9(frame);
      // Since the EndToEndTests use kVicdeoCodecUnknow we treat it the same as
      // kVideoCodecGeneric.
      // TODO(philipel): Take a look at the EndToEndTests and see if maybe they
      //                 should be changed to use kVideoCodecGeneric instead.
      case kVideoCodecUnknown:
      case kVideoCodecH264:
      case kVideoCodecI420:
      case kVideoCodecMultiplex:
      case kVideoCodecGeneric:
        return ManageFrameGeneric(frame, kNoPictureId);
    }
  
    // If not all code paths return a value it makes the win compiler sad.
    RTC_NOTREACHED();
    return kDrop;
  }
  
  void RtpFrameReferenceFinder::PaddingReceived(uint16_t seq_num) {
    rtc::CritScope lock(&crit_);
    auto clean_padding_to =
        stashed_padding_.lower_bound(seq_num - kMaxPaddingAge);
    stashed_padding_.erase(stashed_padding_.begin(), clean_padding_to);
    stashed_padding_.insert(seq_num);
    UpdateLastPictureIdWithPadding(seq_num);
    RetryStashedFrames();
  }
  
  void RtpFrameReferenceFinder::ClearTo(uint16_t seq_num) {
    rtc::CritScope lock(&crit_);
    cleared_to_seq_num_ = seq_num;
  
    auto it = stashed_frames_.begin();
    while (it != stashed_frames_.end()) {
      if (AheadOf<uint16_t>(cleared_to_seq_num_, (*it)->first_seq_num())) {
        it = stashed_frames_.erase(it);
      } else {
        ++it;
      }
    }
  }
  
  void RtpFrameReferenceFinder::UpdateLastPictureIdWithPadding(uint16_t seq_num) {
    auto gop_seq_num_it = last_seq_num_gop_.upper_bound(seq_num);
  
    // If this padding packet "belongs" to a group of pictures that we don't track
    // anymore, do nothing.
    if (gop_seq_num_it == last_seq_num_gop_.begin())
      return;
    --gop_seq_num_it;
  
    // Calculate the next contiuous sequence number and search for it in
    // the padding packets we have stashed.
    uint16_t next_seq_num_with_padding = gop_seq_num_it->second.second + 1;
    auto padding_seq_num_it =
        stashed_padding_.lower_bound(next_seq_num_with_padding);
  
    // While there still are padding packets and those padding packets are
    // continuous, then advance the "last-picture-id-with-padding" and remove
    // the stashed padding packet.
    while (padding_seq_num_it != stashed_padding_.end() &&
           *padding_seq_num_it == next_seq_num_with_padding) {
      gop_seq_num_it->second.second = next_seq_num_with_padding;
      ++next_seq_num_with_padding;
      padding_seq_num_it = stashed_padding_.erase(padding_seq_num_it);
    }
  
    // In the case where the stream has been continuous without any new keyframes
    // for a while there is a risk that new frames will appear to be older than
    // the keyframe they belong to due to wrapping sequence number. In order
    // to prevent this we advance the picture id of the keyframe every so often.
    if (ForwardDiff(gop_seq_num_it->first, seq_num) > 10000) {
      RTC_DCHECK_EQ(1ul, last_seq_num_gop_.size());
      last_seq_num_gop_[seq_num] = gop_seq_num_it->second;
      last_seq_num_gop_.erase(gop_seq_num_it);
    }
  }
  
  RtpFrameReferenceFinder::FrameDecision
  RtpFrameReferenceFinder::ManageFrameGeneric(RtpFrameObject* frame,
                                              int picture_id) {
    // If |picture_id| is specified then we use that to set the frame references,
    // otherwise we use sequence number.
    if (picture_id != kNoPictureId) {
      if (last_unwrap_ == -1)
        last_unwrap_ = picture_id;
  
      frame->id.picture_id = unwrapper_.Unwrap(picture_id);
      frame->num_references = frame->frame_type() == kVideoFrameKey ? 0 : 1;
      frame->references[0] = frame->id.picture_id - 1;
      return kHandOff;
    }
  
    if (frame->frame_type() == kVideoFrameKey) {
      last_seq_num_gop_.insert(std::make_pair(
          frame->last_seq_num(),
          std::make_pair(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())
      return kStash;
  
    // 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);
    for (auto it = last_seq_num_gop_.begin();
         it != clean_to && last_seq_num_gop_.size() > 1;) {
      it = last_seq_num_gop_.erase(it);
    }
  
    // 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());
    if (seq_num_it == last_seq_num_gop_.begin()) {
      RTC_LOG(LS_WARNING) << "Generic frame with packet range ["
                          << frame->first_seq_num() << ", "
                          << frame->last_seq_num()
                          << "] has no GoP, dropping frame.";
      return kDrop;
    }
    seq_num_it--;
  
    // Make sure the packet sequence numbers are continuous, otherwise stash
    // this frame.
    uint16_t last_picture_id_gop = seq_num_it->second.first;
    uint16_t last_picture_id_with_padding_gop = seq_num_it->second.second;
    if (frame->frame_type() == kVideoFrameDelta) {
      uint16_t prev_seq_num = frame->first_seq_num() - 1;
  
      if (prev_seq_num != last_picture_id_with_padding_gop)
        return kStash;
    }
  
    RTC_DCHECK(AheadOrAt(frame->last_seq_num(), seq_num_it->first));
  
    // Since keyframes can cause reordering we can't simply assign the
    // picture id according to some incrementing counter.
    frame->id.picture_id = frame->last_seq_num();
    frame->num_references = frame->frame_type() == kVideoFrameDelta;
    frame->references[0] = generic_unwrapper_.Unwrap(last_picture_id_gop);
    if (AheadOf<uint16_t>(frame->id.picture_id, last_picture_id_gop)) {
      seq_num_it->second.first = frame->id.picture_id;
      seq_num_it->second.second = frame->id.picture_id;
    }
  
    last_picture_id_ = frame->id.picture_id;
    UpdateLastPictureIdWithPadding(frame->id.picture_id);
    frame->id.picture_id = generic_unwrapper_.Unwrap(frame->id.picture_id);
    return kHandOff;
  }
  
  RtpFrameReferenceFinder::FrameDecision RtpFrameReferenceFinder::ManageFrameVp8(
      RtpFrameObject* frame) {
    rtc::Optional<RTPVideoTypeHeader> rtp_codec_header = frame->GetCodecHeader();
    if (!rtp_codec_header) {
      RTC_LOG(LS_WARNING)
          << "Failed to get codec header from frame, dropping frame.";
      return kDrop;
    }
  
    const RTPVideoHeaderVP8& codec_header = rtp_codec_header->VP8;
  
    if (codec_header.pictureId == kNoPictureId ||
        codec_header.temporalIdx == kNoTemporalIdx ||
        codec_header.tl0PicIdx == kNoTl0PicIdx) {
      return ManageFrameGeneric(std::move(frame), codec_header.pictureId);
    }
  
    frame->id.picture_id = codec_header.pictureId % kPicIdLength;
  
    if (last_unwrap_ == -1)
      last_unwrap_ = codec_header.pictureId;
  
    if (last_picture_id_ == -1)
      last_picture_id_ = frame->id.picture_id;
  
    // Find if there has been a gap in fully received frames and save the picture
    // id of those frames in |not_yet_received_frames_|.
    if (AheadOf<uint16_t, kPicIdLength>(frame->id.picture_id, last_picture_id_)) {
      do {
        last_picture_id_ = Add<kPicIdLength>(last_picture_id_, 1);
        not_yet_received_frames_.insert(last_picture_id_);
      } while (last_picture_id_ != frame->id.picture_id);
    }
  
    // 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->id.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 (frame->frame_type() == kVideoFrameKey) {
      frame->num_references = 0;
      layer_info_[codec_header.tl0PicIdx].fill(-1);
      UpdateLayerInfoVp8(frame, codec_header);
      return kHandOff;
    }
  
    auto layer_info_it = layer_info_.find(codec_header.temporalIdx == 0
                                              ? codec_header.tl0PicIdx - 1
                                              : codec_header.tl0PicIdx);
  
    // If we don't have the base layer frame yet, stash this frame.
    if (layer_info_it == layer_info_.end())
      return kStash;
  
    // A non keyframe base layer frame has been received, copy the layer info
    // from the previous base layer frame and set a reference to the previous
    // base layer frame.
    if (codec_header.temporalIdx == 0) {
      layer_info_it =
          layer_info_
              .insert(make_pair(codec_header.tl0PicIdx, layer_info_it->second))
              .first;
      frame->num_references = 1;
      frame->references[0] = layer_info_it->second[0];
      UpdateLayerInfoVp8(frame, codec_header);
      return kHandOff;
    }
  
    // Layer sync frame, this frame only references its base layer frame.
    if (codec_header.layerSync) {
      frame->num_references = 1;
      frame->references[0] = layer_info_it->second[0];
  
      UpdateLayerInfoVp8(frame, codec_header);
      return kHandOff;
    }
  
    // Find all references for this frame.
    frame->num_references = 0;
    for (uint8_t layer = 0; layer <= codec_header.temporalIdx; ++layer) {
      // If we have not yet received a previous frame on this temporal layer,
      // stash this frame.
      if (layer_info_it->second[layer] == -1)
        return kStash;
  
      // If the last frame on this layer is ahead of this frame it means that
      // a layer sync frame has been received after this frame for the same
      // base layer frame, drop this frame.
      if (AheadOf<uint16_t, kPicIdLength>(layer_info_it->second[layer],
                                          frame->id.picture_id)) {
        return kDrop;
      }
  
      // 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]);
      if (not_received_frame_it != not_yet_received_frames_.end() &&
          AheadOf<uint16_t, kPicIdLength>(frame->id.picture_id,
                                          *not_received_frame_it)) {
        return kStash;
      }
  
      if (!(AheadOf<uint16_t, kPicIdLength>(frame->id.picture_id,
                                            layer_info_it->second[layer]))) {
        RTC_LOG(LS_WARNING) << "Frame with picture id " << frame->id.picture_id
                            << " and packet range [" << frame->first_seq_num()
                            << ", " << frame->last_seq_num()
                            << "] already received, "
                            << " dropping frame.";
        return kDrop;
      }
  
      ++frame->num_references;
      frame->references[layer] = layer_info_it->second[layer];
    }
  
    UpdateLayerInfoVp8(frame, codec_header);
    return kHandOff;
  }
  
  void RtpFrameReferenceFinder::UpdateLayerInfoVp8(
      RtpFrameObject* frame,
      const RTPVideoHeaderVP8& codec_header) {
    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->id.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->id.picture_id;
      ++tl0_pic_idx;
      layer_info_it = layer_info_.find(tl0_pic_idx);
    }
    not_yet_received_frames_.erase(frame->id.picture_id);
  
    UnwrapPictureIds(frame);
  }
  
  RtpFrameReferenceFinder::FrameDecision RtpFrameReferenceFinder::ManageFrameVp9(
      RtpFrameObject* frame) {
    rtc::Optional<RTPVideoTypeHeader> rtp_codec_header = frame->GetCodecHeader();
    if (!rtp_codec_header) {
      RTC_LOG(LS_WARNING)
          << "Failed to get codec header from frame, dropping frame.";
      return kDrop;
    }
  
    const RTPVideoHeaderVP9& codec_header = rtp_codec_header->VP9;
  
    if (codec_header.picture_id == kNoPictureId ||
        codec_header.temporal_idx == kNoTemporalIdx) {
      return ManageFrameGeneric(std::move(frame), codec_header.picture_id);
    }
  
    frame->id.spatial_layer = codec_header.spatial_idx;
    frame->inter_layer_predicted = codec_header.inter_layer_predicted;
    frame->id.picture_id = codec_header.picture_id % kPicIdLength;
  
    if (last_unwrap_ == -1)
      last_unwrap_ = codec_header.picture_id;
  
    if (last_picture_id_ == -1)
      last_picture_id_ = frame->id.picture_id;
  
    if (codec_header.flexible_mode) {
      frame->num_references = codec_header.num_ref_pics;
      for (size_t i = 0; i < frame->num_references; ++i) {
        frame->references[i] = Subtract<kPicIdLength>(frame->id.picture_id,
                                                      codec_header.pid_diff[i]);
      }
  
      UnwrapPictureIds(frame);
      return kHandOff;
    }
  
    if (codec_header.ss_data_available) {
      // Scalability structures can only be sent with tl0 frames.
      if (codec_header.temporal_idx != 0) {
        RTC_LOG(LS_WARNING)
            << "Received scalability structure on a non base layer"
               " frame. Scalability structure ignored.";
      } else {
        current_ss_idx_ = Add<kMaxGofSaved>(current_ss_idx_, 1);
        scalability_structures_[current_ss_idx_] = codec_header.gof;
        scalability_structures_[current_ss_idx_].pid_start = frame->id.picture_id;
  
        GofInfo info(&scalability_structures_[current_ss_idx_],
                     frame->id.picture_id);
        gof_info_.insert(std::make_pair(codec_header.tl0_pic_idx, info));
      }
    }
  
    // 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 (frame->frame_type() == kVideoFrameKey) {
      // When using GOF all keyframes must include the scalability structure.
      if (!codec_header.ss_data_available)
        RTC_LOG(LS_WARNING) << "Received keyframe without scalability structure";
  
      frame->num_references = 0;
      GofInfo info = gof_info_.find(codec_header.tl0_pic_idx)->second;
      FrameReceivedVp9(frame->id.picture_id, &info);
      UnwrapPictureIds(frame);
      return kHandOff;
    }
  
    auto gof_info_it = gof_info_.find(
        (codec_header.temporal_idx == 0 && !codec_header.ss_data_available)
            ? codec_header.tl0_pic_idx - 1
            : codec_header.tl0_pic_idx);
  
    // Gof info for this frame is not available yet, stash this frame.
    if (gof_info_it == gof_info_.end())
      return kStash;
  
    GofInfo* info = &gof_info_it->second;
    FrameReceivedVp9(frame->id.picture_id, info);
  
    // Make sure we don't miss any frame that could potentially have the
    // up switch flag set.
    if (MissingRequiredFrameVp9(frame->id.picture_id, *info))
      return kStash;
  
    if (codec_header.temporal_up_switch) {
      auto pid_tidx =
          std::make_pair(frame->id.picture_id, codec_header.temporal_idx);
      up_switch_.insert(pid_tidx);
    }
  
    // If this is a base layer frame that contains a scalability structure
    // then gof info has already been inserted earlier, so we only want to
    // insert if we haven't done so already.
    if (codec_header.temporal_idx == 0 && !codec_header.ss_data_available) {
      GofInfo new_info(info->gof, frame->id.picture_id);
      gof_info_.insert(std::make_pair(codec_header.tl0_pic_idx, new_info));
    }
  
    // Clean out old info about up switch frames.
    uint16_t old_picture_id = Subtract<kPicIdLength>(frame->id.picture_id, 50);
    auto up_switch_erase_to = up_switch_.lower_bound(old_picture_id);
    up_switch_.erase(up_switch_.begin(), up_switch_erase_to);
  
    size_t diff = ForwardDiff<uint16_t, kPicIdLength>(info->gof->pid_start,
                                                      frame->id.picture_id);
    size_t gof_idx = diff % info->gof->num_frames_in_gof;
  
    // Populate references according to the scalability structure.
    frame->num_references = info->gof->num_ref_pics[gof_idx];
    for (size_t i = 0; i < frame->num_references; ++i) {
      frame->references[i] = Subtract<kPicIdLength>(
          frame->id.picture_id, info->gof->pid_diff[gof_idx][i]);
  
      // If this is a reference to a frame earlier than the last up switch point,
      // then ignore this reference.
      if (UpSwitchInIntervalVp9(frame->id.picture_id, codec_header.temporal_idx,
                                frame->references[i])) {
        --frame->num_references;
      }
    }
  
    UnwrapPictureIds(frame);
    return kHandOff;
  }
  
  bool RtpFrameReferenceFinder::MissingRequiredFrameVp9(uint16_t picture_id,
                                                        const GofInfo& info) {
    size_t diff =
        ForwardDiff<uint16_t, kPicIdLength>(info.gof->pid_start, picture_id);
    size_t gof_idx = diff % info.gof->num_frames_in_gof;
    size_t temporal_idx = info.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 = info.gof->num_ref_pics[gof_idx];
    for (size_t i = 0; i < num_references; ++i) {
      uint16_t ref_pid =
          Subtract<kPicIdLength>(picture_id, info.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 RtpFrameReferenceFinder::FrameReceivedVp9(uint16_t picture_id,
                                                 GofInfo* info) {
    int last_picture_id = info->last_picture_id;
    size_t gof_size = std::min(info->gof->num_frames_in_gof, kMaxVp9FramesInGof);
  
    // 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>(info->gof->pid_start,
                                                        last_picture_id);
      size_t gof_idx = diff % gof_size;
  
      last_picture_id = Add<kPicIdLength>(last_picture_id, 1);
      while (last_picture_id != picture_id) {
        gof_idx = (gof_idx  + 1) % gof_size;
        RTC_CHECK(gof_idx < kMaxVp9FramesInGof);
  
        size_t temporal_idx = info->gof->temporal_idx[gof_idx];
        if (temporal_idx >= kMaxTemporalLayers) {
          RTC_LOG(LS_WARNING) << "At most " << kMaxTemporalLayers << " temporal "
                              << "layers are supported.";
          return;
        }
  
        missing_frames_for_layer_[temporal_idx].insert(last_picture_id);
        last_picture_id = Add<kPicIdLength>(last_picture_id, 1);
      }
  
      info->last_picture_id = last_picture_id;
    } else {
      size_t diff =
          ForwardDiff<uint16_t, kPicIdLength>(info->gof->pid_start, picture_id);
      size_t gof_idx = diff % gof_size;
      RTC_CHECK(gof_idx < kMaxVp9FramesInGof);
  
      size_t temporal_idx = info->gof->temporal_idx[gof_idx];
      if (temporal_idx >= kMaxTemporalLayers) {
        RTC_LOG(LS_WARNING) << "At most " << kMaxTemporalLayers << " temporal "
                            << "layers are supported.";
        return;
      }
  
      missing_frames_for_layer_[temporal_idx].erase(picture_id);
    }
  }
  
  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 RtpFrameReferenceFinder::UnwrapPictureIds(RtpFrameObject* frame) {
    for (size_t i = 0; i < frame->num_references; ++i)
      frame->references[i] = unwrapper_.Unwrap(frame->references[i]);
    frame->id.picture_id = unwrapper_.Unwrap(frame->id.picture_id);
  }
  
  }  // namespace video_coding
  }  // namespace webrtc
  