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/*
* Copyright (c) 2020 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_vp9_ref_finder.h"
#include <algorithm>
#include <utility>
#include "rtc_base/logging.h"
namespace webrtc {
RtpFrameReferenceFinder::ReturnVector RtpVp9RefFinder::ManageFrame(
std::unique_ptr<RtpFrameObject> frame) {
const RTPVideoHeaderVP9& codec_header = absl::get<RTPVideoHeaderVP9>(
frame->GetRtpVideoHeader().video_type_header);
if (codec_header.temporal_idx != kNoTemporalIdx)
frame->SetTemporalIndex(codec_header.temporal_idx);
frame->SetSpatialIndex(codec_header.spatial_idx);
frame->SetId(codec_header.picture_id & (kFrameIdLength - 1));
FrameDecision decision;
if (codec_header.temporal_idx >= kMaxTemporalLayers ||
codec_header.spatial_idx >= kMaxSpatialLayers) {
decision = kDrop;
} else if (codec_header.flexible_mode) {
decision = ManageFrameFlexible(frame.get(), codec_header);
} else {
if (codec_header.tl0_pic_idx == kNoTl0PicIdx) {
RTC_LOG(LS_WARNING) << "TL0PICIDX is expected to be present in "
"non-flexible mode.";
decision = kDrop;
} else {
int64_t unwrapped_tl0 =
tl0_unwrapper_.Unwrap(codec_header.tl0_pic_idx & 0xFF);
decision = ManageFrameGof(frame.get(), codec_header, unwrapped_tl0);
if (decision == kStash) {
if (stashed_frames_.size() > kMaxStashedFrames) {
stashed_frames_.pop_back();
}
stashed_frames_.push_front(
{.unwrapped_tl0 = unwrapped_tl0, .frame = std::move(frame)});
}
}
}
RtpFrameReferenceFinder::ReturnVector res;
switch (decision) {
case kStash:
return res;
case kHandOff:
res.push_back(std::move(frame));
RetryStashedFrames(res);
return res;
case kDrop:
return res;
}
return res;
}
RtpVp9RefFinder::FrameDecision RtpVp9RefFinder::ManageFrameFlexible(
RtpFrameObject* frame,
const RTPVideoHeaderVP9& codec_header) {
if (codec_header.num_ref_pics > EncodedFrame::kMaxFrameReferences) {
return kDrop;
}
frame->num_references = codec_header.num_ref_pics;
for (size_t i = 0; i < frame->num_references; ++i) {
frame->references[i] =
Subtract<kFrameIdLength>(frame->Id(), codec_header.pid_diff[i]);
}
FlattenFrameIdAndRefs(frame, codec_header.inter_layer_predicted);
return kHandOff;
}
RtpVp9RefFinder::FrameDecision RtpVp9RefFinder::ManageFrameGof(
RtpFrameObject* frame,
const RTPVideoHeaderVP9& codec_header,
int64_t unwrapped_tl0) {
GofInfo* info;
if (codec_header.ss_data_available) {
if (codec_header.temporal_idx != 0) {
RTC_LOG(LS_WARNING) << "Received scalability structure on a non base "
"layer frame. Scalability structure ignored.";
} else {
if (codec_header.gof.num_frames_in_gof > kMaxVp9FramesInGof) {
return kDrop;
}
for (size_t i = 0; i < codec_header.gof.num_frames_in_gof; ++i) {
if (codec_header.gof.num_ref_pics[i] > kMaxVp9RefPics) {
return kDrop;
}
}
GofInfoVP9 gof = codec_header.gof;
if (gof.num_frames_in_gof == 0) {
RTC_LOG(LS_WARNING) << "Number of frames in GOF is zero. Assume "
"that stream has only one temporal layer.";
gof.SetGofInfoVP9(kTemporalStructureMode1);
}
current_ss_idx_ = Add<kMaxGofSaved>(current_ss_idx_, 1);
scalability_structures_[current_ss_idx_] = gof;
scalability_structures_[current_ss_idx_].pid_start = frame->Id();
gof_info_.emplace(
unwrapped_tl0,
GofInfo(&scalability_structures_[current_ss_idx_], frame->Id()));
}
const auto gof_info_it = gof_info_.find(unwrapped_tl0);
if (gof_info_it == gof_info_.end())
return kStash;
info = &gof_info_it->second;
if (frame->frame_type() == VideoFrameType::kVideoFrameKey) {
frame->num_references = 0;
FrameReceivedVp9(frame->Id(), info);
FlattenFrameIdAndRefs(frame, codec_header.inter_layer_predicted);
return kHandOff;
}
} else {
if (frame->frame_type() == VideoFrameType::kVideoFrameKey) {
RTC_LOG(LS_WARNING) << "Received keyframe without scalability structure";
return kDrop;
}
// tl0_idx is incremented on temporal_idx=0 frames of the lowest spatial
// layer (which spatial_idx is not necessarily zero). Upper spatial layer
// frames with inter-layer prediction use GOF info of their base spatial
// layer frames.
const bool use_prev_gof =
codec_header.temporal_idx == 0 && !codec_header.inter_layer_predicted;
auto gof_info_it =
gof_info_.find(use_prev_gof ? unwrapped_tl0 - 1 : unwrapped_tl0);
// Gof info for this frame is not available yet, stash this frame.
if (gof_info_it == gof_info_.end())
return kStash;
if (codec_header.temporal_idx == 0) {
gof_info_it = gof_info_
.emplace(unwrapped_tl0,
GofInfo(gof_info_it->second.gof, frame->Id()))
.first;
}
info = &gof_info_it->second;
}
// Clean up info for base layers that are too old.
int64_t old_tl0_pic_idx = unwrapped_tl0 - kMaxGofSaved;
auto clean_gof_info_to = gof_info_.lower_bound(old_tl0_pic_idx);
gof_info_.erase(gof_info_.begin(), clean_gof_info_to);
FrameReceivedVp9(frame->Id(), info);
// Make sure we don't miss any frame that could potentially have the
// up switch flag set.
if (MissingRequiredFrameVp9(frame->Id(), *info))
return kStash;
if (codec_header.temporal_up_switch)
up_switch_.emplace(frame->Id(), codec_header.temporal_idx);
// Clean out old info about up switch frames.
uint16_t old_picture_id = Subtract<kFrameIdLength>(frame->Id(), 50);
auto up_switch_erase_to = up_switch_.lower_bound(old_picture_id);
up_switch_.erase(up_switch_.begin(), up_switch_erase_to);
if (codec_header.inter_pic_predicted) {
size_t diff = ForwardDiff<uint16_t, kFrameIdLength>(info->gof->pid_start,
frame->Id());
size_t gof_idx = diff % info->gof->num_frames_in_gof;
if (info->gof->num_ref_pics[gof_idx] > EncodedFrame::kMaxFrameReferences) {
return kDrop;
}
// 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<kFrameIdLength>(
frame->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(), codec_header.temporal_idx,
frame->references[i])) {
--frame->num_references;
}
}
} else {
frame->num_references = 0;
}
FlattenFrameIdAndRefs(frame, codec_header.inter_layer_predicted);
return kHandOff;
}
bool RtpVp9RefFinder::MissingRequiredFrameVp9(uint16_t picture_id,
const GofInfo& info) {
size_t diff =
ForwardDiff<uint16_t, kFrameIdLength>(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];
if (temporal_idx >= kMaxTemporalLayers) {
RTC_LOG(LS_WARNING) << "At most " << kMaxTemporalLayers
<< " temporal "
"layers are supported.";
return true;
}
// 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<kFrameIdLength>(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, kFrameIdLength>(picture_id, *missing_frame_it)) {
return true;
}
}
}
return false;
}
void RtpVp9RefFinder::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, kFrameIdLength>(picture_id, last_picture_id)) {
size_t diff = ForwardDiff<uint16_t, kFrameIdLength>(info->gof->pid_start,
last_picture_id);
size_t gof_idx = diff % gof_size;
last_picture_id = Add<kFrameIdLength>(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<kFrameIdLength>(last_picture_id, 1);
}
info->last_picture_id = last_picture_id;
} else {
size_t diff =
ForwardDiff<uint16_t, kFrameIdLength>(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 RtpVp9RefFinder::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, kFrameIdLength>(picture_id, up_switch_it->first);
++up_switch_it) {
if (up_switch_it->second < temporal_idx)
return true;
}
return false;
}
void RtpVp9RefFinder::RetryStashedFrames(
RtpFrameReferenceFinder::ReturnVector& res) {
bool complete_frame = false;
do {
complete_frame = false;
for (auto it = stashed_frames_.begin(); it != stashed_frames_.end();) {
const RTPVideoHeaderVP9& codec_header = absl::get<RTPVideoHeaderVP9>(
it->frame->GetRtpVideoHeader().video_type_header);
RTC_DCHECK(!codec_header.flexible_mode);
FrameDecision decision =
ManageFrameGof(it->frame.get(), codec_header, it->unwrapped_tl0);
switch (decision) {
case kStash:
++it;
break;
case kHandOff:
complete_frame = true;
res.push_back(std::move(it->frame));
[[fallthrough]];
case kDrop:
it = stashed_frames_.erase(it);
}
}
} while (complete_frame);
}
void RtpVp9RefFinder::FlattenFrameIdAndRefs(RtpFrameObject* frame,
bool inter_layer_predicted) {
for (size_t i = 0; i < frame->num_references; ++i) {
frame->references[i] =
unwrapper_.Unwrap(frame->references[i]) * kMaxSpatialLayers +
*frame->SpatialIndex();
}
frame->SetId(unwrapper_.Unwrap(frame->Id()) * kMaxSpatialLayers +
*frame->SpatialIndex());
if (inter_layer_predicted &&
frame->num_references + 1 <= EncodedFrame::kMaxFrameReferences) {
frame->references[frame->num_references] = frame->Id() - 1;
++frame->num_references;
}
}
void RtpVp9RefFinder::ClearTo(uint16_t seq_num) {
auto it = stashed_frames_.begin();
while (it != stashed_frames_.end()) {
if (AheadOf<uint16_t>(seq_num, it->frame->first_seq_num())) {
it = stashed_frames_.erase(it);
} else {
++it;
}
}
}
} // namespace webrtc