Revert "Running FrameBuffer on task queue."
This reverts commit 13943b7b7f6d00568912b9969db2c7871d18e21f.
Reason for revert: Breaks chromium import bots:
https://ci.chromium.org/p/chromium/builders/webrtc.fyi/WebRTC%20Chromium%20FYI%20Android%20Tests%20%28dbg%29%20%28K%20Nexus5%29
First failure:
https://ci.chromium.org/p/chromium/builders/webrtc.fyi/WebRTC%20Chromium%20FYI%20Android%20Tests%20%28dbg%29%20%28K%20Nexus5%29/2794
Original change's description:
> Running FrameBuffer on task queue.
>
> This prepares for running WebRTC in simulated time where event::Wait
> based timing doesn't work.
>
> Bug: webrtc:10365
> Change-Id: Ia0f9b1cc8e3c8c27a38e45b40487050a4699d8cf
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/129962
> Reviewed-by: Philip Eliasson <philipel@webrtc.org>
> Reviewed-by: Erik Språng <sprang@webrtc.org>
> Commit-Queue: Sebastian Jansson <srte@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#27422}
TBR=sprang@webrtc.org,philipel@webrtc.org,srte@webrtc.org
Change-Id: I198a91ec1707cc8752a7fe55caf0f172e1b8e60a
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:10365
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/131120
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27436}diff --git a/modules/video_coding/frame_buffer2.cc b/modules/video_coding/frame_buffer2.cc
index a654019..ecc0e17 100644
--- a/modules/video_coding/frame_buffer2.cc
+++ b/modules/video_coding/frame_buffer2.cc
@@ -17,8 +17,6 @@
#include <utility>
#include <vector>
-#include "absl/memory/memory.h"
-#include "api/task_queue/global_task_queue_factory.h"
#include "api/video/encoded_image.h"
#include "api/video/video_timing.h"
#include "modules/video_coding/include/video_coding_defines.h"
@@ -47,30 +45,14 @@
constexpr int kMaxAllowedFrameDelayMs = 5;
constexpr int64_t kLogNonDecodedIntervalMs = 5000;
-
-std::unique_ptr<TaskQueueBase, TaskQueueDeleter> CreateQueue(
- TaskQueueFactory* task_queue_factory) {
- if (!task_queue_factory)
- task_queue_factory = &GlobalTaskQueueFactory();
- return task_queue_factory->CreateTaskQueue("FrameBuffer",
- TaskQueueFactory::Priority::HIGH);
-}
} // namespace
FrameBuffer::FrameBuffer(Clock* clock,
VCMJitterEstimator* jitter_estimator,
VCMTiming* timing,
- VCMReceiveStatisticsCallback* stats_proxy)
- : FrameBuffer(clock, nullptr, jitter_estimator, timing, stats_proxy) {}
-
-FrameBuffer::FrameBuffer(Clock* clock,
- TaskQueueFactory* task_queue_factory,
- VCMJitterEstimator* jitter_estimator,
- VCMTiming* timing,
VCMReceiveStatisticsCallback* stats_callback)
: decoded_frames_history_(kMaxFramesHistory),
clock_(clock),
- use_task_queue_(task_queue_factory != nullptr),
jitter_estimator_(jitter_estimator),
timing_(timing),
inter_frame_delay_(clock_->TimeInMilliseconds()),
@@ -79,69 +61,14 @@
stats_callback_(stats_callback),
last_log_non_decoded_ms_(-kLogNonDecodedIntervalMs),
add_rtt_to_playout_delay_(
- webrtc::field_trial::IsEnabled("WebRTC-AddRttToPlayoutDelay")),
- task_queue_(CreateQueue(task_queue_factory)) {}
+ webrtc::field_trial::IsEnabled("WebRTC-AddRttToPlayoutDelay")) {}
FrameBuffer::~FrameBuffer() {}
-void FrameBuffer::NextFrame(
- int64_t max_wait_time_ms,
- bool keyframe_required,
- std::function<void(std::unique_ptr<EncodedFrame>, ReturnReason)> handler) {
- RTC_DCHECK(use_task_queue_);
- TRACE_EVENT0("webrtc", "FrameBuffer::NextFrame");
- int64_t latest_return_time_ms =
- clock_->TimeInMilliseconds() + max_wait_time_ms;
- task_queue_.PostTask([=] {
- RTC_DCHECK_RUN_ON(&task_queue_);
- rtc::CritScope lock(&crit_);
- if (stopped_) {
- return;
- }
- latest_return_time_ms_ = latest_return_time_ms;
- keyframe_required_ = keyframe_required;
- frame_handler_ = handler;
- NextFrameOnQueue();
- });
-}
-
-void FrameBuffer::NextFrameOnQueue() {
- RTC_DCHECK(use_task_queue_);
- RTC_DCHECK(!callback_task_.Running());
- int64_t wait_ms = UpdateFramesToDecode(clock_->TimeInMilliseconds());
- callback_task_ = RepeatingTaskHandle::DelayedStart(
- task_queue_.Get(), TimeDelta::ms(wait_ms), [this] {
- // If this task has not been cancelled, we did not get any new frames
- // while waiting. Continue with frame delivery.
- RTC_DCHECK_RUN_ON(&task_queue_);
- rtc::CritScope lock(&crit_);
- if (!frames_to_decode_.empty()) {
- // We have frames, deliver!
- frame_handler_(absl::WrapUnique(GetFrameToDecode()), kFrameFound);
- frame_handler_ = {};
- callback_task_.Stop();
- return TimeDelta::Zero(); // Ignored.
- } else if (clock_->TimeInMilliseconds() >= latest_return_time_ms_) {
- // We have timed out, signal this and stop repeating.
- frame_handler_(nullptr, kTimeout);
- frame_handler_ = {};
- callback_task_.Stop();
- return TimeDelta::Zero(); // Ignored.
- } else {
- // If there's no frames to decode and there is still time left, it
- // means that the frame buffer was cleared between creation and
- // execution of this task. Continue waiting for the remaining time.
- int64_t wait_ms = UpdateFramesToDecode(clock_->TimeInMilliseconds());
- return TimeDelta::ms(wait_ms);
- }
- });
-}
-
FrameBuffer::ReturnReason FrameBuffer::NextFrame(
int64_t max_wait_time_ms,
std::unique_ptr<EncodedFrame>* frame_out,
bool keyframe_required) {
- RTC_DCHECK(!use_task_queue_);
TRACE_EVENT0("webrtc", "FrameBuffer::NextFrame");
int64_t latest_return_time_ms =
clock_->TimeInMilliseconds() + max_wait_time_ms;
@@ -156,25 +83,183 @@
if (stopped_)
return kStopped;
- // Need to hold |crit_| in order to access the members. therefore we
+ wait_ms = max_wait_time_ms;
+
+ // Need to hold |crit_| in order to access frames_to_decode_. therefore we
// set it here in the loop instead of outside the loop in order to not
// acquire the lock unnecessarily.
- keyframe_required_ = keyframe_required;
- latest_return_time_ms_ = latest_return_time_ms;
- wait_ms = UpdateFramesToDecode(now_ms);
- }
+ frames_to_decode_.clear();
+
+ // |last_continuous_frame_| may be empty below, but nullopt is smaller
+ // than everything else and loop will immediately terminate as expected.
+ for (auto frame_it = frames_.begin();
+ frame_it != frames_.end() &&
+ frame_it->first <= last_continuous_frame_;
+ ++frame_it) {
+ if (!frame_it->second.continuous ||
+ frame_it->second.num_missing_decodable > 0) {
+ continue;
+ }
+
+ EncodedFrame* frame = frame_it->second.frame.get();
+
+ if (keyframe_required && !frame->is_keyframe())
+ continue;
+
+ auto last_decoded_frame_timestamp =
+ decoded_frames_history_.GetLastDecodedFrameTimestamp();
+
+ // TODO(https://bugs.webrtc.org/9974): consider removing this check
+ // as it may make a stream undecodable after a very long delay between
+ // frames.
+ if (last_decoded_frame_timestamp &&
+ AheadOf(*last_decoded_frame_timestamp, frame->Timestamp())) {
+ continue;
+ }
+
+ // Only ever return all parts of a superframe. Therefore skip this
+ // frame if it's not a beginning of a superframe.
+ if (frame->inter_layer_predicted) {
+ continue;
+ }
+
+ // Gather all remaining frames for the same superframe.
+ std::vector<FrameMap::iterator> current_superframe;
+ current_superframe.push_back(frame_it);
+ bool last_layer_completed =
+ frame_it->second.frame->is_last_spatial_layer;
+ FrameMap::iterator next_frame_it = frame_it;
+ while (true) {
+ ++next_frame_it;
+ if (next_frame_it == frames_.end() ||
+ next_frame_it->first.picture_id != frame->id.picture_id ||
+ !next_frame_it->second.continuous) {
+ break;
+ }
+ // Check if the next frame has some undecoded references other than
+ // the previous frame in the same superframe.
+ size_t num_allowed_undecoded_refs =
+ (next_frame_it->second.frame->inter_layer_predicted) ? 1 : 0;
+ if (next_frame_it->second.num_missing_decodable >
+ num_allowed_undecoded_refs) {
+ break;
+ }
+ // All frames in the superframe should have the same timestamp.
+ if (frame->Timestamp() != next_frame_it->second.frame->Timestamp()) {
+ RTC_LOG(LS_WARNING)
+ << "Frames in a single superframe have different"
+ " timestamps. Skipping undecodable superframe.";
+ break;
+ }
+ current_superframe.push_back(next_frame_it);
+ last_layer_completed =
+ next_frame_it->second.frame->is_last_spatial_layer;
+ }
+ // Check if the current superframe is complete.
+ // TODO(bugs.webrtc.org/10064): consider returning all available to
+ // decode frames even if the superframe is not complete yet.
+ if (!last_layer_completed) {
+ continue;
+ }
+
+ frames_to_decode_ = std::move(current_superframe);
+
+ if (frame->RenderTime() == -1) {
+ frame->SetRenderTime(
+ timing_->RenderTimeMs(frame->Timestamp(), now_ms));
+ }
+ wait_ms = timing_->MaxWaitingTime(frame->RenderTime(), now_ms);
+
+ // This will cause the frame buffer to prefer high framerate rather
+ // than high resolution in the case of the decoder not decoding fast
+ // enough and the stream has multiple spatial and temporal layers.
+ // For multiple temporal layers it may cause non-base layer frames to be
+ // skipped if they are late.
+ if (wait_ms < -kMaxAllowedFrameDelayMs)
+ continue;
+
+ break;
+ }
+ } // rtc::Critscope lock(&crit_);
+
+ wait_ms = std::min<int64_t>(wait_ms, latest_return_time_ms - now_ms);
+ wait_ms = std::max<int64_t>(wait_ms, 0);
} while (new_continuous_frame_event_.Wait(wait_ms));
{
rtc::CritScope lock(&crit_);
+ now_ms = clock_->TimeInMilliseconds();
+ // TODO(ilnik): remove |frames_out| use frames_to_decode_ directly.
+ std::vector<EncodedFrame*> frames_out;
if (!frames_to_decode_.empty()) {
- frame_out->reset(GetFrameToDecode());
+ bool superframe_delayed_by_retransmission = false;
+ size_t superframe_size = 0;
+ EncodedFrame* first_frame = frames_to_decode_[0]->second.frame.get();
+ int64_t render_time_ms = first_frame->RenderTime();
+ int64_t receive_time_ms = first_frame->ReceivedTime();
+ // Gracefully handle bad RTP timestamps and render time issues.
+ if (HasBadRenderTiming(*first_frame, now_ms)) {
+ jitter_estimator_->Reset();
+ timing_->Reset();
+ render_time_ms =
+ timing_->RenderTimeMs(first_frame->Timestamp(), now_ms);
+ }
+
+ for (FrameMap::iterator& frame_it : frames_to_decode_) {
+ RTC_DCHECK(frame_it != frames_.end());
+ EncodedFrame* frame = frame_it->second.frame.release();
+
+ frame->SetRenderTime(render_time_ms);
+
+ superframe_delayed_by_retransmission |=
+ frame->delayed_by_retransmission();
+ receive_time_ms = std::max(receive_time_ms, frame->ReceivedTime());
+ superframe_size += frame->size();
+
+ PropagateDecodability(frame_it->second);
+ decoded_frames_history_.InsertDecoded(frame_it->first,
+ frame->Timestamp());
+
+ // Remove decoded frame and all undecoded frames before it.
+ frames_.erase(frames_.begin(), ++frame_it);
+
+ frames_out.push_back(frame);
+ }
+
+ if (!superframe_delayed_by_retransmission) {
+ int64_t frame_delay;
+
+ if (inter_frame_delay_.CalculateDelay(first_frame->Timestamp(),
+ &frame_delay, receive_time_ms)) {
+ jitter_estimator_->UpdateEstimate(frame_delay, superframe_size);
+ }
+
+ float rtt_mult = protection_mode_ == kProtectionNackFEC ? 0.0 : 1.0;
+ if (RttMultExperiment::RttMultEnabled()) {
+ rtt_mult = RttMultExperiment::GetRttMultValue();
+ }
+ timing_->SetJitterDelay(jitter_estimator_->GetJitterEstimate(rtt_mult));
+ timing_->UpdateCurrentDelay(render_time_ms, now_ms);
+ } else {
+ if (RttMultExperiment::RttMultEnabled() || add_rtt_to_playout_delay_)
+ jitter_estimator_->FrameNacked();
+ }
+
+ UpdateJitterDelay();
+ UpdateTimingFrameInfo();
+ }
+ if (!frames_out.empty()) {
+ if (frames_out.size() == 1) {
+ frame_out->reset(frames_out[0]);
+ } else {
+ frame_out->reset(CombineAndDeleteFrames(frames_out));
+ }
return kFrameFound;
}
- }
+ } // rtc::Critscope lock(&crit_)
- if (latest_return_time_ms - clock_->TimeInMilliseconds() > 0) {
+ if (latest_return_time_ms - now_ms > 0) {
// If |next_frame_it_ == frames_.end()| and there is still time left, it
// means that the frame buffer was cleared as the thread in this function
// was waiting to acquire |crit_| in order to return. Wait for the
@@ -184,166 +269,6 @@
return kTimeout;
}
-int64_t FrameBuffer::UpdateFramesToDecode(int64_t now_ms) {
- int64_t wait_ms = latest_return_time_ms_ - now_ms;
- frames_to_decode_.clear();
-
- // |last_continuous_frame_| may be empty below, but nullopt is smaller
- // than everything else and loop will immediately terminate as expected.
- for (auto frame_it = frames_.begin();
- frame_it != frames_.end() && frame_it->first <= last_continuous_frame_;
- ++frame_it) {
- if (!frame_it->second.continuous ||
- frame_it->second.num_missing_decodable > 0) {
- continue;
- }
-
- EncodedFrame* frame = frame_it->second.frame.get();
-
- if (keyframe_required_ && !frame->is_keyframe())
- continue;
-
- auto last_decoded_frame_timestamp =
- decoded_frames_history_.GetLastDecodedFrameTimestamp();
-
- // TODO(https://bugs.webrtc.org/9974): consider removing this check
- // as it may make a stream undecodable after a very long delay between
- // frames.
- if (last_decoded_frame_timestamp &&
- AheadOf(*last_decoded_frame_timestamp, frame->Timestamp())) {
- continue;
- }
-
- // Only ever return all parts of a superframe. Therefore skip this
- // frame if it's not a beginning of a superframe.
- if (frame->inter_layer_predicted) {
- continue;
- }
-
- // Gather all remaining frames for the same superframe.
- std::vector<FrameMap::iterator> current_superframe;
- current_superframe.push_back(frame_it);
- bool last_layer_completed = frame_it->second.frame->is_last_spatial_layer;
- FrameMap::iterator next_frame_it = frame_it;
- while (true) {
- ++next_frame_it;
- if (next_frame_it == frames_.end() ||
- next_frame_it->first.picture_id != frame->id.picture_id ||
- !next_frame_it->second.continuous) {
- break;
- }
- // Check if the next frame has some undecoded references other than
- // the previous frame in the same superframe.
- size_t num_allowed_undecoded_refs =
- (next_frame_it->second.frame->inter_layer_predicted) ? 1 : 0;
- if (next_frame_it->second.num_missing_decodable >
- num_allowed_undecoded_refs) {
- break;
- }
- // All frames in the superframe should have the same timestamp.
- if (frame->Timestamp() != next_frame_it->second.frame->Timestamp()) {
- RTC_LOG(LS_WARNING) << "Frames in a single superframe have different"
- " timestamps. Skipping undecodable superframe.";
- break;
- }
- current_superframe.push_back(next_frame_it);
- last_layer_completed = next_frame_it->second.frame->is_last_spatial_layer;
- }
- // Check if the current superframe is complete.
- // TODO(bugs.webrtc.org/10064): consider returning all available to
- // decode frames even if the superframe is not complete yet.
- if (!last_layer_completed) {
- continue;
- }
-
- frames_to_decode_ = std::move(current_superframe);
-
- if (frame->RenderTime() == -1) {
- frame->SetRenderTime(timing_->RenderTimeMs(frame->Timestamp(), now_ms));
- }
- wait_ms = timing_->MaxWaitingTime(frame->RenderTime(), now_ms);
-
- // This will cause the frame buffer to prefer high framerate rather
- // than high resolution in the case of the decoder not decoding fast
- // enough and the stream has multiple spatial and temporal layers.
- // For multiple temporal layers it may cause non-base layer frames to be
- // skipped if they are late.
- if (wait_ms < -kMaxAllowedFrameDelayMs)
- continue;
-
- break;
- }
- wait_ms = std::min<int64_t>(wait_ms, latest_return_time_ms_ - now_ms);
- wait_ms = std::max<int64_t>(wait_ms, 0);
- return wait_ms;
-}
-
-EncodedFrame* FrameBuffer::GetFrameToDecode() {
- int64_t now_ms = clock_->TimeInMilliseconds();
- // TODO(ilnik): remove |frames_out| use frames_to_decode_ directly.
- std::vector<EncodedFrame*> frames_out;
-
- RTC_DCHECK(!frames_to_decode_.empty());
- bool superframe_delayed_by_retransmission = false;
- size_t superframe_size = 0;
- EncodedFrame* first_frame = frames_to_decode_[0]->second.frame.get();
- int64_t render_time_ms = first_frame->RenderTime();
- int64_t receive_time_ms = first_frame->ReceivedTime();
- // Gracefully handle bad RTP timestamps and render time issues.
- if (HasBadRenderTiming(*first_frame, now_ms)) {
- jitter_estimator_->Reset();
- timing_->Reset();
- render_time_ms = timing_->RenderTimeMs(first_frame->Timestamp(), now_ms);
- }
-
- for (FrameMap::iterator& frame_it : frames_to_decode_) {
- RTC_DCHECK(frame_it != frames_.end());
- EncodedFrame* frame = frame_it->second.frame.release();
-
- frame->SetRenderTime(render_time_ms);
-
- superframe_delayed_by_retransmission |= frame->delayed_by_retransmission();
- receive_time_ms = std::max(receive_time_ms, frame->ReceivedTime());
- superframe_size += frame->size();
-
- PropagateDecodability(frame_it->second);
- decoded_frames_history_.InsertDecoded(frame_it->first, frame->Timestamp());
-
- // Remove decoded frame and all undecoded frames before it.
- frames_.erase(frames_.begin(), ++frame_it);
-
- frames_out.push_back(frame);
- }
-
- if (!superframe_delayed_by_retransmission) {
- int64_t frame_delay;
-
- if (inter_frame_delay_.CalculateDelay(first_frame->Timestamp(),
- &frame_delay, receive_time_ms)) {
- jitter_estimator_->UpdateEstimate(frame_delay, superframe_size);
- }
-
- float rtt_mult = protection_mode_ == kProtectionNackFEC ? 0.0 : 1.0;
- if (RttMultExperiment::RttMultEnabled()) {
- rtt_mult = RttMultExperiment::GetRttMultValue();
- }
- timing_->SetJitterDelay(jitter_estimator_->GetJitterEstimate(rtt_mult));
- timing_->UpdateCurrentDelay(render_time_ms, now_ms);
- } else {
- if (RttMultExperiment::RttMultEnabled() || add_rtt_to_playout_delay_)
- jitter_estimator_->FrameNacked();
- }
-
- UpdateJitterDelay();
- UpdateTimingFrameInfo();
-
- if (frames_out.size() == 1) {
- return frames_out[0];
- } else {
- return CombineAndDeleteFrames(frames_out);
- }
-}
-
bool FrameBuffer::HasBadRenderTiming(const EncodedFrame& frame,
int64_t now_ms) {
// Assume that render timing errors are due to changes in the video stream.
@@ -372,63 +297,33 @@
return false;
}
-void FrameBuffer::SafePost(std::function<void()> func) {
- if (!use_task_queue_) {
- func();
- } else {
- task_queue_.PostTask(func);
- }
-}
void FrameBuffer::SetProtectionMode(VCMVideoProtection mode) {
TRACE_EVENT0("webrtc", "FrameBuffer::SetProtectionMode");
- SafePost([this, mode] {
- rtc::CritScope lock(&crit_);
- protection_mode_ = mode;
- });
+ rtc::CritScope lock(&crit_);
+ protection_mode_ = mode;
}
void FrameBuffer::Start() {
TRACE_EVENT0("webrtc", "FrameBuffer::Start");
- SafePost([this] {
- rtc::CritScope lock(&crit_);
- stopped_ = false;
- });
+ rtc::CritScope lock(&crit_);
+ stopped_ = false;
}
void FrameBuffer::Stop() {
TRACE_EVENT0("webrtc", "FrameBuffer::Stop");
- if (!use_task_queue_) {
- rtc::CritScope lock(&crit_);
- stopped_ = true;
- new_continuous_frame_event_.Set();
- } else {
- rtc::Event done;
- task_queue_.PostTask([this, &done] {
- rtc::CritScope lock(&crit_);
- stopped_ = true;
- if (frame_handler_) {
- RTC_DCHECK(callback_task_.Running());
- callback_task_.Stop();
- frame_handler_ = {};
- }
- done.Set();
- });
- done.Wait(rtc::Event::kForever);
- }
+ rtc::CritScope lock(&crit_);
+ stopped_ = true;
+ new_continuous_frame_event_.Set();
}
void FrameBuffer::Clear() {
- SafePost([this] {
- rtc::CritScope lock(&crit_);
- ClearFramesAndHistory();
- });
+ rtc::CritScope lock(&crit_);
+ ClearFramesAndHistory();
}
void FrameBuffer::UpdateRtt(int64_t rtt_ms) {
- SafePost([this, rtt_ms] {
- rtc::CritScope lock(&crit_);
- jitter_estimator_->UpdateRtt(rtt_ms);
- });
+ rtc::CritScope lock(&crit_);
+ jitter_estimator_->UpdateRtt(rtt_ms);
}
bool FrameBuffer::ValidReferences(const EncodedFrame& frame) const {
@@ -489,22 +384,6 @@
return true;
}
-void FrameBuffer::InsertFrame(std::unique_ptr<EncodedFrame> frame,
- std::function<void(int64_t)> picture_id_handler) {
- struct InsertFrameTask {
- void operator()() {
- RTC_DCHECK_RUN_ON(&frame_buffer->task_queue_);
- int64_t last_continuous_pid = frame_buffer->InsertFrame(std::move(frame));
- picture_id_handler(last_continuous_pid);
- }
- FrameBuffer* frame_buffer;
- std::unique_ptr<EncodedFrame> frame;
- std::function<void(int64_t)> picture_id_handler;
- };
- task_queue_.PostTask(
- InsertFrameTask{this, std::move(frame), std::move(picture_id_handler)});
-}
-
int64_t FrameBuffer::InsertFrame(std::unique_ptr<EncodedFrame> frame) {
TRACE_EVENT0("webrtc", "FrameBuffer::InsertFrame");
RTC_DCHECK(frame);
@@ -608,14 +487,9 @@
last_continuous_picture_id = last_continuous_frame_->picture_id;
// Since we now have new continuous frames there might be a better frame
- // to return from NextFrame.
- if (!use_task_queue_) {
- new_continuous_frame_event_.Set();
- } else if (callback_task_.Running()) {
- RTC_CHECK(frame_handler_);
- callback_task_.Stop();
- NextFrameOnQueue();
- }
+ // to return from NextFrame. Signal that thread so that it again can choose
+ // which frame to return.
+ new_continuous_frame_event_.Set();
}
return last_continuous_picture_id;