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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/svc/scalability_structure_key_svc.h"
#include <bitset>
#include <utility>
#include <vector>
#include "absl/types/optional.h"
#include "api/transport/rtp/dependency_descriptor.h"
#include "api/video/video_bitrate_allocation.h"
#include "common_video/generic_frame_descriptor/generic_frame_info.h"
#include "modules/video_coding/svc/scalable_video_controller.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
namespace webrtc {
constexpr int ScalabilityStructureKeySvc::kMaxNumSpatialLayers;
constexpr int ScalabilityStructureKeySvc::kMaxNumTemporalLayers;
ScalabilityStructureKeySvc::ScalabilityStructureKeySvc(int num_spatial_layers,
int num_temporal_layers)
: num_spatial_layers_(num_spatial_layers),
num_temporal_layers_(num_temporal_layers),
active_decode_targets_(
(uint32_t{1} << (num_spatial_layers * num_temporal_layers)) - 1) {
// There is no point to use this structure without spatial scalability.
RTC_DCHECK_GT(num_spatial_layers, 1);
RTC_DCHECK_LE(num_spatial_layers, kMaxNumSpatialLayers);
RTC_DCHECK_LE(num_temporal_layers, kMaxNumTemporalLayers);
}
ScalabilityStructureKeySvc::~ScalabilityStructureKeySvc() = default;
ScalableVideoController::StreamLayersConfig
ScalabilityStructureKeySvc::StreamConfig() const {
StreamLayersConfig result;
result.num_spatial_layers = num_spatial_layers_;
result.num_temporal_layers = num_temporal_layers_;
result.scaling_factor_num[num_spatial_layers_ - 1] = 1;
result.scaling_factor_den[num_spatial_layers_ - 1] = 1;
for (int sid = num_spatial_layers_ - 1; sid > 0; --sid) {
result.scaling_factor_num[sid - 1] = 1;
result.scaling_factor_den[sid - 1] = 2 * result.scaling_factor_den[sid];
}
result.uses_reference_scaling = true;
return result;
}
bool ScalabilityStructureKeySvc::TemporalLayerIsActive(int tid) const {
if (tid >= num_temporal_layers_) {
return false;
}
for (int sid = 0; sid < num_spatial_layers_; ++sid) {
if (DecodeTargetIsActive(sid, tid)) {
return true;
}
}
return false;
}
DecodeTargetIndication ScalabilityStructureKeySvc::Dti(
int sid,
int tid,
const LayerFrameConfig& config) {
if (config.IsKeyframe() || config.Id() == kKey) {
RTC_DCHECK_EQ(config.TemporalId(), 0);
return sid < config.SpatialId() ? DecodeTargetIndication::kNotPresent
: DecodeTargetIndication::kSwitch;
}
if (sid != config.SpatialId() || tid < config.TemporalId()) {
return DecodeTargetIndication::kNotPresent;
}
if (tid == config.TemporalId() && tid > 0) {
return DecodeTargetIndication::kDiscardable;
}
return DecodeTargetIndication::kSwitch;
}
std::vector<ScalableVideoController::LayerFrameConfig>
ScalabilityStructureKeySvc::KeyframeConfig() {
std::vector<LayerFrameConfig> configs;
configs.reserve(num_spatial_layers_);
absl::optional<int> spatial_dependency_buffer_id;
spatial_id_is_enabled_.reset();
// Disallow temporal references cross T0 on higher temporal layers.
can_reference_t1_frame_for_spatial_id_.reset();
for (int sid = 0; sid < num_spatial_layers_; ++sid) {
if (!DecodeTargetIsActive(sid, /*tid=*/0)) {
continue;
}
configs.emplace_back();
ScalableVideoController::LayerFrameConfig& config = configs.back();
config.Id(kKey).S(sid).T(0);
if (spatial_dependency_buffer_id) {
config.Reference(*spatial_dependency_buffer_id);
} else {
config.Keyframe();
}
config.Update(BufferIndex(sid, /*tid=*/0));
spatial_id_is_enabled_.set(sid);
spatial_dependency_buffer_id = BufferIndex(sid, /*tid=*/0);
}
return configs;
}
std::vector<ScalableVideoController::LayerFrameConfig>
ScalabilityStructureKeySvc::T0Config() {
std::vector<LayerFrameConfig> configs;
configs.reserve(num_spatial_layers_);
// Disallow temporal references cross T0 on higher temporal layers.
can_reference_t1_frame_for_spatial_id_.reset();
for (int sid = 0; sid < num_spatial_layers_; ++sid) {
if (!DecodeTargetIsActive(sid, /*tid=*/0)) {
spatial_id_is_enabled_.reset(sid);
continue;
}
configs.emplace_back();
configs.back().Id(kDeltaT0).S(sid).T(0).ReferenceAndUpdate(
BufferIndex(sid, /*tid=*/0));
}
return configs;
}
std::vector<ScalableVideoController::LayerFrameConfig>
ScalabilityStructureKeySvc::T1Config() {
std::vector<LayerFrameConfig> configs;
configs.reserve(num_spatial_layers_);
for (int sid = 0; sid < num_spatial_layers_; ++sid) {
if (!DecodeTargetIsActive(sid, /*tid=*/1)) {
continue;
}
configs.emplace_back();
ScalableVideoController::LayerFrameConfig& config = configs.back();
config.Id(kDeltaT1).S(sid).T(1).Reference(BufferIndex(sid, /*tid=*/0));
if (num_temporal_layers_ > 2) {
config.Update(BufferIndex(sid, /*tid=*/1));
}
}
return configs;
}
std::vector<ScalableVideoController::LayerFrameConfig>
ScalabilityStructureKeySvc::T2Config(FramePattern pattern) {
std::vector<LayerFrameConfig> configs;
configs.reserve(num_spatial_layers_);
for (int sid = 0; sid < num_spatial_layers_; ++sid) {
if (!DecodeTargetIsActive(sid, /*tid=*/2)) {
continue;
}
configs.emplace_back();
ScalableVideoController::LayerFrameConfig& config = configs.back();
config.Id(pattern).S(sid).T(2);
if (can_reference_t1_frame_for_spatial_id_[sid]) {
config.Reference(BufferIndex(sid, /*tid=*/1));
} else {
config.Reference(BufferIndex(sid, /*tid=*/0));
}
}
return configs;
}
ScalabilityStructureKeySvc::FramePattern
ScalabilityStructureKeySvc::NextPattern(FramePattern last_pattern) const {
switch (last_pattern) {
case kNone:
return kKey;
case kDeltaT2B:
return kDeltaT0;
case kDeltaT2A:
if (TemporalLayerIsActive(1)) {
return kDeltaT1;
}
return kDeltaT0;
case kDeltaT1:
if (TemporalLayerIsActive(2)) {
return kDeltaT2B;
}
return kDeltaT0;
case kDeltaT0:
case kKey:
if (TemporalLayerIsActive(2)) {
return kDeltaT2A;
}
if (TemporalLayerIsActive(1)) {
return kDeltaT1;
}
return kDeltaT0;
}
RTC_DCHECK_NOTREACHED();
return kNone;
}
std::vector<ScalableVideoController::LayerFrameConfig>
ScalabilityStructureKeySvc::NextFrameConfig(bool restart) {
if (active_decode_targets_.none()) {
last_pattern_ = kNone;
return {};
}
if (restart) {
last_pattern_ = kNone;
}
FramePattern current_pattern = NextPattern(last_pattern_);
switch (current_pattern) {
case kKey:
return KeyframeConfig();
case kDeltaT0:
return T0Config();
case kDeltaT1:
return T1Config();
case kDeltaT2A:
case kDeltaT2B:
return T2Config(current_pattern);
case kNone:
break;
}
RTC_DCHECK_NOTREACHED();
return {};
}
GenericFrameInfo ScalabilityStructureKeySvc::OnEncodeDone(
const LayerFrameConfig& config) {
// When encoder drops all frames for a temporal unit, it is better to reuse
// old temporal pattern rather than switch to next one, thus switch to next
// pattern defered here from the `NextFrameConfig`.
// In particular creating VP9 references rely on this behavior.
last_pattern_ = static_cast<FramePattern>(config.Id());
if (config.TemporalId() == 1) {
can_reference_t1_frame_for_spatial_id_.set(config.SpatialId());
}
GenericFrameInfo frame_info;
frame_info.spatial_id = config.SpatialId();
frame_info.temporal_id = config.TemporalId();
frame_info.encoder_buffers = config.Buffers();
frame_info.decode_target_indications.reserve(num_spatial_layers_ *
num_temporal_layers_);
for (int sid = 0; sid < num_spatial_layers_; ++sid) {
for (int tid = 0; tid < num_temporal_layers_; ++tid) {
frame_info.decode_target_indications.push_back(Dti(sid, tid, config));
}
}
frame_info.part_of_chain.assign(num_spatial_layers_, false);
if (config.IsKeyframe() || config.Id() == kKey) {
RTC_DCHECK_EQ(config.TemporalId(), 0);
for (int sid = config.SpatialId(); sid < num_spatial_layers_; ++sid) {
frame_info.part_of_chain[sid] = true;
}
} else if (config.TemporalId() == 0) {
frame_info.part_of_chain[config.SpatialId()] = true;
}
frame_info.active_decode_targets = active_decode_targets_;
return frame_info;
}
void ScalabilityStructureKeySvc::OnRatesUpdated(
const VideoBitrateAllocation& bitrates) {
for (int sid = 0; sid < num_spatial_layers_; ++sid) {
// Enable/disable spatial layers independetely.
bool active = bitrates.GetBitrate(sid, /*tid=*/0) > 0;
SetDecodeTargetIsActive(sid, /*tid=*/0, active);
if (!spatial_id_is_enabled_[sid] && active) {
// Key frame is required to reenable any spatial layer.
last_pattern_ = kNone;
}
for (int tid = 1; tid < num_temporal_layers_; ++tid) {
// To enable temporal layer, require bitrates for lower temporal layers.
active = active && bitrates.GetBitrate(sid, tid) > 0;
SetDecodeTargetIsActive(sid, tid, active);
}
}
}
ScalabilityStructureL2T1Key::~ScalabilityStructureL2T1Key() = default;
FrameDependencyStructure ScalabilityStructureL2T1Key::DependencyStructure()
const {
FrameDependencyStructure structure;
structure.num_decode_targets = 2;
structure.num_chains = 2;
structure.decode_target_protected_by_chain = {0, 1};
structure.templates.resize(4);
structure.templates[0].S(0).Dtis("S-").ChainDiffs({2, 1}).FrameDiffs({2});
structure.templates[1].S(0).Dtis("SS").ChainDiffs({0, 0});
structure.templates[2].S(1).Dtis("-S").ChainDiffs({1, 2}).FrameDiffs({2});
structure.templates[3].S(1).Dtis("-S").ChainDiffs({1, 1}).FrameDiffs({1});
return structure;
}
ScalabilityStructureL2T2Key::~ScalabilityStructureL2T2Key() = default;
FrameDependencyStructure ScalabilityStructureL2T2Key::DependencyStructure()
const {
FrameDependencyStructure structure;
structure.num_decode_targets = 4;
structure.num_chains = 2;
structure.decode_target_protected_by_chain = {0, 0, 1, 1};
structure.templates.resize(6);
auto& templates = structure.templates;
templates[0].S(0).T(0).Dtis("SSSS").ChainDiffs({0, 0});
templates[1].S(0).T(0).Dtis("SS--").ChainDiffs({4, 3}).FrameDiffs({4});
templates[2].S(0).T(1).Dtis("-D--").ChainDiffs({2, 1}).FrameDiffs({2});
templates[3].S(1).T(0).Dtis("--SS").ChainDiffs({1, 1}).FrameDiffs({1});
templates[4].S(1).T(0).Dtis("--SS").ChainDiffs({1, 4}).FrameDiffs({4});
templates[5].S(1).T(1).Dtis("---D").ChainDiffs({3, 2}).FrameDiffs({2});
return structure;
}
ScalabilityStructureL2T3Key::~ScalabilityStructureL2T3Key() = default;
FrameDependencyStructure ScalabilityStructureL2T3Key::DependencyStructure()
const {
FrameDependencyStructure structure;
structure.num_decode_targets = 6;
structure.num_chains = 2;
structure.decode_target_protected_by_chain = {0, 0, 0, 1, 1, 1};
auto& templates = structure.templates;
templates.resize(10);
templates[0].S(0).T(0).Dtis("SSSSSS").ChainDiffs({0, 0});
templates[1].S(0).T(0).Dtis("SSS---").ChainDiffs({8, 7}).FrameDiffs({8});
templates[2].S(0).T(1).Dtis("-DS---").ChainDiffs({4, 3}).FrameDiffs({4});
templates[3].S(0).T(2).Dtis("--D---").ChainDiffs({2, 1}).FrameDiffs({2});
templates[4].S(0).T(2).Dtis("--D---").ChainDiffs({6, 5}).FrameDiffs({2});
templates[5].S(1).T(0).Dtis("---SSS").ChainDiffs({1, 1}).FrameDiffs({1});
templates[6].S(1).T(0).Dtis("---SSS").ChainDiffs({1, 8}).FrameDiffs({8});
templates[7].S(1).T(1).Dtis("----DS").ChainDiffs({5, 4}).FrameDiffs({4});
templates[8].S(1).T(2).Dtis("-----D").ChainDiffs({3, 2}).FrameDiffs({2});
templates[9].S(1).T(2).Dtis("-----D").ChainDiffs({7, 6}).FrameDiffs({2});
return structure;
}
ScalabilityStructureL3T1Key::~ScalabilityStructureL3T1Key() = default;
FrameDependencyStructure ScalabilityStructureL3T1Key::DependencyStructure()
const {
FrameDependencyStructure structure;
structure.num_decode_targets = 3;
structure.num_chains = 3;
structure.decode_target_protected_by_chain = {0, 1, 2};
auto& t = structure.templates;
t.resize(6);
// Templates are shown in the order frames following them appear in the
// stream, but in `structure.templates` array templates are sorted by
// (`spatial_id`, `temporal_id`) since that is a dependency descriptor
// requirement.
t[1].S(0).Dtis("SSS").ChainDiffs({0, 0, 0});
t[3].S(1).Dtis("-SS").ChainDiffs({1, 1, 1}).FrameDiffs({1});
t[5].S(2).Dtis("--S").ChainDiffs({2, 1, 1}).FrameDiffs({1});
t[0].S(0).Dtis("S--").ChainDiffs({3, 2, 1}).FrameDiffs({3});
t[2].S(1).Dtis("-S-").ChainDiffs({1, 3, 2}).FrameDiffs({3});
t[4].S(2).Dtis("--S").ChainDiffs({2, 1, 3}).FrameDiffs({3});
return structure;
}
ScalabilityStructureL3T2Key::~ScalabilityStructureL3T2Key() = default;
FrameDependencyStructure ScalabilityStructureL3T2Key::DependencyStructure()
const {
FrameDependencyStructure structure;
structure.num_decode_targets = 6;
structure.num_chains = 3;
structure.decode_target_protected_by_chain = {0, 0, 1, 1, 2, 2};
auto& t = structure.templates;
t.resize(9);
// Templates are shown in the order frames following them appear in the
// stream, but in `structure.templates` array templates are sorted by
// (`spatial_id`, `temporal_id`) since that is a dependency descriptor
// requirement.
t[1].S(0).T(0).Dtis("SSSSSS").ChainDiffs({0, 0, 0});
t[4].S(1).T(0).Dtis("--SSSS").ChainDiffs({1, 1, 1}).FrameDiffs({1});
t[7].S(2).T(0).Dtis("----SS").ChainDiffs({2, 1, 1}).FrameDiffs({1});
t[2].S(0).T(1).Dtis("-D----").ChainDiffs({3, 2, 1}).FrameDiffs({3});
t[5].S(1).T(1).Dtis("---D--").ChainDiffs({4, 3, 2}).FrameDiffs({3});
t[8].S(2).T(1).Dtis("-----D").ChainDiffs({5, 4, 3}).FrameDiffs({3});
t[0].S(0).T(0).Dtis("SS----").ChainDiffs({6, 5, 4}).FrameDiffs({6});
t[3].S(1).T(0).Dtis("--SS--").ChainDiffs({1, 6, 5}).FrameDiffs({6});
t[6].S(2).T(0).Dtis("----SS").ChainDiffs({2, 1, 6}).FrameDiffs({6});
return structure;
}
ScalabilityStructureL3T3Key::~ScalabilityStructureL3T3Key() = default;
FrameDependencyStructure ScalabilityStructureL3T3Key::DependencyStructure()
const {
FrameDependencyStructure structure;
structure.num_decode_targets = 9;
structure.num_chains = 3;
structure.decode_target_protected_by_chain = {0, 0, 0, 1, 1, 1, 2, 2, 2};
auto& t = structure.templates;
t.resize(15);
// Templates are shown in the order frames following them appear in the
// stream, but in `structure.templates` array templates are sorted by
// (`spatial_id`, `temporal_id`) since that is a dependency descriptor
// requirement. Indexes are written in hex for nicer alignment.
t[0x0].S(0).T(0).Dtis("SSSSSSSSS").ChainDiffs({0, 0, 0});
t[0x5].S(1).T(0).Dtis("---SSSSSS").ChainDiffs({1, 1, 1}).FrameDiffs({1});
t[0xA].S(2).T(0).Dtis("------SSS").ChainDiffs({2, 1, 1}).FrameDiffs({1});
t[0x3].S(0).T(2).Dtis("--D------").ChainDiffs({3, 2, 1}).FrameDiffs({3});
t[0x8].S(1).T(2).Dtis("-----D---").ChainDiffs({4, 3, 2}).FrameDiffs({3});
t[0xD].S(2).T(2).Dtis("--------D").ChainDiffs({5, 4, 3}).FrameDiffs({3});
t[0x2].S(0).T(1).Dtis("-DS------").ChainDiffs({6, 5, 4}).FrameDiffs({6});
t[0x7].S(1).T(1).Dtis("----DS---").ChainDiffs({7, 6, 5}).FrameDiffs({6});
t[0xC].S(2).T(1).Dtis("-------DS").ChainDiffs({8, 7, 6}).FrameDiffs({6});
t[0x4].S(0).T(2).Dtis("--D------").ChainDiffs({9, 8, 7}).FrameDiffs({3});
t[0x9].S(1).T(2).Dtis("-----D---").ChainDiffs({10, 9, 8}).FrameDiffs({3});
t[0xE].S(2).T(2).Dtis("--------D").ChainDiffs({11, 10, 9}).FrameDiffs({3});
t[0x1].S(0).T(0).Dtis("SSS------").ChainDiffs({12, 11, 10}).FrameDiffs({12});
t[0x6].S(1).T(0).Dtis("---SSS---").ChainDiffs({1, 12, 11}).FrameDiffs({12});
t[0xB].S(2).T(0).Dtis("------SSS").ChainDiffs({2, 1, 12}).FrameDiffs({12});
return structure;
}
} // namespace webrtc