webrtc/modules/pacing/paced_sender.cc - platform/external/webrtc - Git at Google

 /*
  *  Copyright (c) 2012 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/pacing/include/paced_sender.h"

 #include <assert.h>

 #include <map>
 #include <queue>
 #include <set>

 #include "webrtc/modules/interface/module_common_types.h"
 #include "webrtc/modules/pacing/bitrate_prober.h"
 #include "webrtc/system_wrappers/include/clock.h"
 #include "webrtc/system_wrappers/include/critical_section_wrapper.h"
 #include "webrtc/system_wrappers/include/field_trial.h"
 #include "webrtc/system_wrappers/include/logging.h"

 namespace {
 // Time limit in milliseconds between packet bursts.
 const int64_t kMinPacketLimitMs = 5;

 // Upper cap on process interval, in case process has not been called in a long
 // time.
 const int64_t kMaxIntervalTimeMs = 30;

 }  // namespace

 namespace webrtc {
 namespace paced_sender {
 struct Packet {
   Packet(RtpPacketSender::Priority priority,
          uint32_t ssrc,
          uint16_t seq_number,
          int64_t capture_time_ms,
          int64_t enqueue_time_ms,
          size_t length_in_bytes,
          bool retransmission,
          uint64_t enqueue_order)
       : priority(priority),
         ssrc(ssrc),
         sequence_number(seq_number),
         capture_time_ms(capture_time_ms),
         enqueue_time_ms(enqueue_time_ms),
         bytes(length_in_bytes),
         retransmission(retransmission),
         enqueue_order(enqueue_order) {}

   RtpPacketSender::Priority priority;
   uint32_t ssrc;
   uint16_t sequence_number;
   int64_t capture_time_ms;
   int64_t enqueue_time_ms;
   size_t bytes;
   bool retransmission;
   uint64_t enqueue_order;
   std::list<Packet>::iterator this_it;
 };

 // Used by priority queue to sort packets.
 struct Comparator {
   bool operator()(const Packet* first, const Packet* second) {
     // Highest prio = 0.
     if (first->priority != second->priority)
       return first->priority > second->priority;

     // Retransmissions go first.
     if (second->retransmission && !first->retransmission)
       return true;

     // Older frames have higher prio.
     if (first->capture_time_ms != second->capture_time_ms)
       return first->capture_time_ms > second->capture_time_ms;

     return first->enqueue_order > second->enqueue_order;
   }
 };

 // Class encapsulating a priority queue with some extensions.
 class PacketQueue {
  public:
   PacketQueue() : bytes_(0) {}
   virtual ~PacketQueue() {}

   void Push(const Packet& packet) {
     if (!AddToDupeSet(packet)) {
       return;
     }
     // Store packet in list, use pointers in priority queue for cheaper moves.
     // Packets have a handle to its own iterator in the list, for easy removal
     // when popping from queue.
     packet_list_.push_front(packet);
     std::list<Packet>::iterator it = packet_list_.begin();
     it->this_it = it;          // Handle for direct removal from list.
     prio_queue_.push(&(*it));  // Pointer into list.
     bytes_ += packet.bytes;
   }

   const Packet& BeginPop() {
     const Packet& packet = *prio_queue_.top();
     prio_queue_.pop();
     return packet;
   }

   void CancelPop(const Packet& packet) { prio_queue_.push(&(*packet.this_it)); }

   void FinalizePop(const Packet& packet) {
     RemoveFromDupeSet(packet);
     bytes_ -= packet.bytes;
     packet_list_.erase(packet.this_it);
   }

   bool Empty() const { return prio_queue_.empty(); }

   size_t SizeInPackets() const { return prio_queue_.size(); }

   uint64_t SizeInBytes() const { return bytes_; }

   int64_t OldestEnqueueTime() const {
     std::list<Packet>::const_reverse_iterator it = packet_list_.rbegin();
     if (it == packet_list_.rend())
       return 0;
     return it->enqueue_time_ms;
   }

  private:
   // Try to add a packet to the set of ssrc/seqno identifiers currently in the
   // queue. Return true if inserted, false if this is a duplicate.
   bool AddToDupeSet(const Packet& packet) {
     SsrcSeqNoMap::iterator it = dupe_map_.find(packet.ssrc);
     if (it == dupe_map_.end()) {
       // First for this ssrc, just insert.
       dupe_map_[packet.ssrc].insert(packet.sequence_number);
       return true;
     }

     // Insert returns a pair, where second is a bool set to true if new element.
     return it->second.insert(packet.sequence_number).second;
   }

   void RemoveFromDupeSet(const Packet& packet) {
     SsrcSeqNoMap::iterator it = dupe_map_.find(packet.ssrc);
     assert(it != dupe_map_.end());
     it->second.erase(packet.sequence_number);
     if (it->second.empty()) {
       dupe_map_.erase(it);
     }
   }

   // List of packets, in the order the were enqueued. Since dequeueing may
   // occur out of order, use list instead of vector.
   std::list<Packet> packet_list_;
   // Priority queue of the packets, sorted according to Comparator.
   // Use pointers into list, to avoid moving whole struct within heap.
   std::priority_queue<Packet*, std::vector<Packet*>, Comparator> prio_queue_;
   // Total number of bytes in the queue.
   uint64_t bytes_;
   // Map<ssrc, set<seq_no> >, for checking duplicates.
   typedef std::map<uint32_t, std::set<uint16_t> > SsrcSeqNoMap;
   SsrcSeqNoMap dupe_map_;
 };

 class IntervalBudget {
  public:
   explicit IntervalBudget(int initial_target_rate_kbps)
       : target_rate_kbps_(initial_target_rate_kbps),
         bytes_remaining_(0) {}

   void set_target_rate_kbps(int target_rate_kbps) {
     target_rate_kbps_ = target_rate_kbps;
     bytes_remaining_ =
         std::max(-kWindowMs * target_rate_kbps_ / 8, bytes_remaining_);
   }

   void IncreaseBudget(int64_t delta_time_ms) {
     int64_t bytes = target_rate_kbps_ * delta_time_ms / 8;
     if (bytes_remaining_ < 0) {
       // We overused last interval, compensate this interval.
       bytes_remaining_ = bytes_remaining_ + bytes;
     } else {
       // If we underused last interval we can't use it this interval.
       bytes_remaining_ = bytes;
     }
   }

   void UseBudget(size_t bytes) {
     bytes_remaining_ = std::max(bytes_remaining_ - static_cast<int>(bytes),
                                 -kWindowMs * target_rate_kbps_ / 8);
   }

   size_t bytes_remaining() const {
     return static_cast<size_t>(std::max(0, bytes_remaining_));
   }

   int target_rate_kbps() const { return target_rate_kbps_; }

  private:
   static const int kWindowMs = 500;

   int target_rate_kbps_;
   int bytes_remaining_;
 };
 }  // namespace paced_sender

 const float PacedSender::kDefaultPaceMultiplier = 2.5f;

 PacedSender::PacedSender(Clock* clock,
                          Callback* callback,
                          int bitrate_kbps,
                          int max_bitrate_kbps,
                          int min_bitrate_kbps)
     : clock_(clock),
       callback_(callback),
       critsect_(CriticalSectionWrapper::CreateCriticalSection()),
       paused_(false),
       probing_enabled_(true),
       media_budget_(new paced_sender::IntervalBudget(max_bitrate_kbps)),
       padding_budget_(new paced_sender::IntervalBudget(min_bitrate_kbps)),
       prober_(new BitrateProber()),
       bitrate_bps_(1000 * bitrate_kbps),
       time_last_update_us_(clock->TimeInMicroseconds()),
       packets_(new paced_sender::PacketQueue()),
       packet_counter_(0) {
   UpdateBytesPerInterval(kMinPacketLimitMs);
 }

 PacedSender::~PacedSender() {}

 void PacedSender::Pause() {
   CriticalSectionScoped cs(critsect_.get());
   paused_ = true;
 }

 void PacedSender::Resume() {
   CriticalSectionScoped cs(critsect_.get());
   paused_ = false;
 }

 void PacedSender::SetProbingEnabled(bool enabled) {
   assert(packet_counter_ == 0);
   probing_enabled_ = enabled;
 }

 void PacedSender::UpdateBitrate(int bitrate_kbps,
                                 int max_bitrate_kbps,
                                 int min_bitrate_kbps) {
   CriticalSectionScoped cs(critsect_.get());
   media_budget_->set_target_rate_kbps(max_bitrate_kbps);
   padding_budget_->set_target_rate_kbps(min_bitrate_kbps);
   bitrate_bps_ = 1000 * bitrate_kbps;
 }

 void PacedSender::InsertPacket(RtpPacketSender::Priority priority,
                                uint32_t ssrc,
                                uint16_t sequence_number,
                                int64_t capture_time_ms,
                                size_t bytes,
                                bool retransmission) {
   CriticalSectionScoped cs(critsect_.get());

   if (probing_enabled_ && !prober_->IsProbing()) {
     prober_->SetEnabled(true);
   }
   prober_->MaybeInitializeProbe(bitrate_bps_);

   if (capture_time_ms < 0) {
     capture_time_ms = clock_->TimeInMilliseconds();
   }

   packets_->Push(paced_sender::Packet(
       priority, ssrc, sequence_number, capture_time_ms,
       clock_->TimeInMilliseconds(), bytes, retransmission, packet_counter_++));
 }

 int64_t PacedSender::ExpectedQueueTimeMs() const {
   CriticalSectionScoped cs(critsect_.get());
   int target_rate = media_budget_->target_rate_kbps();
   assert(target_rate > 0);
   return static_cast<int64_t>(packets_->SizeInBytes() * 8 / target_rate);
 }

 size_t PacedSender::QueueSizePackets() const {
   CriticalSectionScoped cs(critsect_.get());
   return packets_->SizeInPackets();
 }

 int64_t PacedSender::QueueInMs() const {
   CriticalSectionScoped cs(critsect_.get());

   int64_t oldest_packet = packets_->OldestEnqueueTime();
   if (oldest_packet == 0)
     return 0;

   return clock_->TimeInMilliseconds() - oldest_packet;
 }

 int64_t PacedSender::TimeUntilNextProcess() {
   CriticalSectionScoped cs(critsect_.get());
   if (prober_->IsProbing()) {
     int64_t ret = prober_->TimeUntilNextProbe(clock_->TimeInMilliseconds());
     if (ret >= 0) {
       return ret;
     }
   }
   int64_t elapsed_time_us = clock_->TimeInMicroseconds() - time_last_update_us_;
   int64_t elapsed_time_ms = (elapsed_time_us + 500) / 1000;
   return std::max<int64_t>(kMinPacketLimitMs - elapsed_time_ms, 0);
 }

 int32_t PacedSender::Process() {
   int64_t now_us = clock_->TimeInMicroseconds();
   CriticalSectionScoped cs(critsect_.get());
   int64_t elapsed_time_ms = (now_us - time_last_update_us_ + 500) / 1000;
   time_last_update_us_ = now_us;
   if (paused_)
     return 0;
   if (elapsed_time_ms > 0) {
     int64_t delta_time_ms = std::min(kMaxIntervalTimeMs, elapsed_time_ms);
     UpdateBytesPerInterval(delta_time_ms);
   }
   while (!packets_->Empty()) {
     if (media_budget_->bytes_remaining() == 0 && !prober_->IsProbing()) {
       return 0;
     }

     // Since we need to release the lock in order to send, we first pop the
     // element from the priority queue but keep it in storage, so that we can
     // reinsert it if send fails.
     const paced_sender::Packet& packet = packets_->BeginPop();
     if (SendPacket(packet)) {
       // Send succeeded, remove it from the queue.
       packets_->FinalizePop(packet);
       if (prober_->IsProbing()) {
         return 0;
       }
     } else {
       // Send failed, put it back into the queue.
       packets_->CancelPop(packet);
       return 0;
     }
   }

   if (!packets_->Empty())
     return 0;

   size_t padding_needed;
   if (prober_->IsProbing())
     padding_needed = prober_->RecommendedPacketSize();
   else
     padding_needed = padding_budget_->bytes_remaining();

   if (padding_needed > 0)
     SendPadding(static_cast<size_t>(padding_needed));
   return 0;
 }

 bool PacedSender::SendPacket(const paced_sender::Packet& packet) {
   critsect_->Leave();
   const bool success = callback_->TimeToSendPacket(packet.ssrc,
                                                    packet.sequence_number,
                                                    packet.capture_time_ms,
                                                    packet.retransmission);
   critsect_->Enter();

   if (success) {
     // Update media bytes sent.
     prober_->PacketSent(clock_->TimeInMilliseconds(), packet.bytes);
     media_budget_->UseBudget(packet.bytes);
     padding_budget_->UseBudget(packet.bytes);
   }

   return success;
 }

 void PacedSender::SendPadding(size_t padding_needed) {
   critsect_->Leave();
   size_t bytes_sent = callback_->TimeToSendPadding(padding_needed);
   critsect_->Enter();

   if (bytes_sent > 0) {
     prober_->PacketSent(clock_->TimeInMilliseconds(), bytes_sent);
     media_budget_->UseBudget(bytes_sent);
     padding_budget_->UseBudget(bytes_sent);
   }
 }

 void PacedSender::UpdateBytesPerInterval(int64_t delta_time_ms) {
   media_budget_->IncreaseBudget(delta_time_ms);
   padding_budget_->IncreaseBudget(delta_time_ms);
 }
 }  // namespace webrtc
	/*
	* Copyright (c) 2012 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/pacing/include/paced_sender.h"

	#include <assert.h>

	#include <map>
	#include <queue>
	#include <set>

	#include "webrtc/modules/interface/module_common_types.h"
	#include "webrtc/modules/pacing/bitrate_prober.h"
	#include "webrtc/system_wrappers/include/clock.h"
	#include "webrtc/system_wrappers/include/critical_section_wrapper.h"
	#include "webrtc/system_wrappers/include/field_trial.h"
	#include "webrtc/system_wrappers/include/logging.h"

	namespace {
	// Time limit in milliseconds between packet bursts.
	const int64_t kMinPacketLimitMs = 5;

	// Upper cap on process interval, in case process has not been called in a long
	// time.
	const int64_t kMaxIntervalTimeMs = 30;

	} // namespace

	namespace webrtc {
	namespace paced_sender {
	struct Packet {
	Packet(RtpPacketSender::Priority priority,
	uint32_t ssrc,
	uint16_t seq_number,
	int64_t capture_time_ms,
	int64_t enqueue_time_ms,
	size_t length_in_bytes,
	bool retransmission,
	uint64_t enqueue_order)
	: priority(priority),
	ssrc(ssrc),
	sequence_number(seq_number),
	capture_time_ms(capture_time_ms),
	enqueue_time_ms(enqueue_time_ms),
	bytes(length_in_bytes),
	retransmission(retransmission),
	enqueue_order(enqueue_order) {}

	RtpPacketSender::Priority priority;
	uint32_t ssrc;
	uint16_t sequence_number;
	int64_t capture_time_ms;
	int64_t enqueue_time_ms;
	size_t bytes;
	bool retransmission;
	uint64_t enqueue_order;
	std::list<Packet>::iterator this_it;
	};

	// Used by priority queue to sort packets.
	struct Comparator {
	bool operator()(const Packet* first, const Packet* second) {
	// Highest prio = 0.
	if (first->priority != second->priority)
	return first->priority > second->priority;

	// Retransmissions go first.
	if (second->retransmission && !first->retransmission)
	return true;

	// Older frames have higher prio.
	if (first->capture_time_ms != second->capture_time_ms)
	return first->capture_time_ms > second->capture_time_ms;

	return first->enqueue_order > second->enqueue_order;
	}
	};

	// Class encapsulating a priority queue with some extensions.
	class PacketQueue {
	public:
	PacketQueue() : bytes_(0) {}
	virtual ~PacketQueue() {}

	void Push(const Packet& packet) {
	if (!AddToDupeSet(packet)) {
	return;
	}
	// Store packet in list, use pointers in priority queue for cheaper moves.
	// Packets have a handle to its own iterator in the list, for easy removal
	// when popping from queue.
	packet_list_.push_front(packet);
	std::list<Packet>::iterator it = packet_list_.begin();
	it->this_it = it; // Handle for direct removal from list.
	prio_queue_.push(&(*it)); // Pointer into list.
	bytes_ += packet.bytes;
	}

	const Packet& BeginPop() {
	const Packet& packet = *prio_queue_.top();
	prio_queue_.pop();
	return packet;
	}

	void CancelPop(const Packet& packet) { prio_queue_.push(&(*packet.this_it)); }

	void FinalizePop(const Packet& packet) {
	RemoveFromDupeSet(packet);
	bytes_ -= packet.bytes;
	packet_list_.erase(packet.this_it);
	}

	bool Empty() const { return prio_queue_.empty(); }

	size_t SizeInPackets() const { return prio_queue_.size(); }

	uint64_t SizeInBytes() const { return bytes_; }

	int64_t OldestEnqueueTime() const {
	std::list<Packet>::const_reverse_iterator it = packet_list_.rbegin();
	if (it == packet_list_.rend())
	return 0;
	return it->enqueue_time_ms;
	}

	private:
	// Try to add a packet to the set of ssrc/seqno identifiers currently in the
	// queue. Return true if inserted, false if this is a duplicate.
	bool AddToDupeSet(const Packet& packet) {
	SsrcSeqNoMap::iterator it = dupe_map_.find(packet.ssrc);
	if (it == dupe_map_.end()) {
	// First for this ssrc, just insert.
	dupe_map_[packet.ssrc].insert(packet.sequence_number);
	return true;
	}

	// Insert returns a pair, where second is a bool set to true if new element.
	return it->second.insert(packet.sequence_number).second;
	}

	void RemoveFromDupeSet(const Packet& packet) {
	SsrcSeqNoMap::iterator it = dupe_map_.find(packet.ssrc);
	assert(it != dupe_map_.end());
	it->second.erase(packet.sequence_number);
	if (it->second.empty()) {
	dupe_map_.erase(it);
	}
	}

	// List of packets, in the order the were enqueued. Since dequeueing may
	// occur out of order, use list instead of vector.
	std::list<Packet> packet_list_;
	// Priority queue of the packets, sorted according to Comparator.
	// Use pointers into list, to avoid moving whole struct within heap.
	std::priority_queue<Packet, std::vector<Packet>, Comparator> prio_queue_;
	// Total number of bytes in the queue.
	uint64_t bytes_;
	// Map<ssrc, set<seq_no> >, for checking duplicates.
	typedef std::map<uint32_t, std::set<uint16_t> > SsrcSeqNoMap;
	SsrcSeqNoMap dupe_map_;
	};

	class IntervalBudget {
	public:
	explicit IntervalBudget(int initial_target_rate_kbps)
	: target_rate_kbps_(initial_target_rate_kbps),
	bytes_remaining_(0) {}

	void set_target_rate_kbps(int target_rate_kbps) {
	target_rate_kbps_ = target_rate_kbps;
	bytes_remaining_ =
	std::max(-kWindowMs * target_rate_kbps_ / 8, bytes_remaining_);
	}

	void IncreaseBudget(int64_t delta_time_ms) {
	int64_t bytes = target_rate_kbps_ * delta_time_ms / 8;
	if (bytes_remaining_ < 0) {
	// We overused last interval, compensate this interval.
	bytes_remaining_ = bytes_remaining_ + bytes;
	} else {
	// If we underused last interval we can't use it this interval.
	bytes_remaining_ = bytes;
	}
	}

	void UseBudget(size_t bytes) {
	bytes_remaining_ = std::max(bytes_remaining_ - static_cast<int>(bytes),
	-kWindowMs * target_rate_kbps_ / 8);
	}

	size_t bytes_remaining() const {
	return static_cast<size_t>(std::max(0, bytes_remaining_));
	}

	int target_rate_kbps() const { return target_rate_kbps_; }

	private:
	static const int kWindowMs = 500;

	int target_rate_kbps_;
	int bytes_remaining_;
	};
	} // namespace paced_sender

	const float PacedSender::kDefaultPaceMultiplier = 2.5f;

	PacedSender::PacedSender(Clock* clock,
	Callback* callback,
	int bitrate_kbps,
	int max_bitrate_kbps,
	int min_bitrate_kbps)
	: clock_(clock),
	callback_(callback),
	critsect_(CriticalSectionWrapper::CreateCriticalSection()),
	paused_(false),
	probing_enabled_(true),
	media_budget_(new paced_sender::IntervalBudget(max_bitrate_kbps)),
	padding_budget_(new paced_sender::IntervalBudget(min_bitrate_kbps)),
	prober_(new BitrateProber()),
	bitrate_bps_(1000 * bitrate_kbps),
	time_last_update_us_(clock->TimeInMicroseconds()),
	packets_(new paced_sender::PacketQueue()),
	packet_counter_(0) {
	UpdateBytesPerInterval(kMinPacketLimitMs);
	}

	PacedSender::~PacedSender() {}

	void PacedSender::Pause() {
	CriticalSectionScoped cs(critsect_.get());
	paused_ = true;
	}

	void PacedSender::Resume() {
	CriticalSectionScoped cs(critsect_.get());
	paused_ = false;
	}

	void PacedSender::SetProbingEnabled(bool enabled) {
	assert(packet_counter_ == 0);
	probing_enabled_ = enabled;
	}

	void PacedSender::UpdateBitrate(int bitrate_kbps,
	int max_bitrate_kbps,
	int min_bitrate_kbps) {
	CriticalSectionScoped cs(critsect_.get());
	media_budget_->set_target_rate_kbps(max_bitrate_kbps);
	padding_budget_->set_target_rate_kbps(min_bitrate_kbps);
	bitrate_bps_ = 1000 * bitrate_kbps;
	}

	void PacedSender::InsertPacket(RtpPacketSender::Priority priority,
	uint32_t ssrc,
	uint16_t sequence_number,
	int64_t capture_time_ms,
	size_t bytes,
	bool retransmission) {
	CriticalSectionScoped cs(critsect_.get());

	if (probing_enabled_ && !prober_->IsProbing()) {
	prober_->SetEnabled(true);
	}
	prober_->MaybeInitializeProbe(bitrate_bps_);

	if (capture_time_ms < 0) {
	capture_time_ms = clock_->TimeInMilliseconds();
	}

	packets_->Push(paced_sender::Packet(
	priority, ssrc, sequence_number, capture_time_ms,
	clock_->TimeInMilliseconds(), bytes, retransmission, packet_counter_++));
	}

	int64_t PacedSender::ExpectedQueueTimeMs() const {
	CriticalSectionScoped cs(critsect_.get());
	int target_rate = media_budget_->target_rate_kbps();
	assert(target_rate > 0);
	return static_cast<int64_t>(packets_->SizeInBytes() * 8 / target_rate);
	}

	size_t PacedSender::QueueSizePackets() const {
	CriticalSectionScoped cs(critsect_.get());
	return packets_->SizeInPackets();
	}

	int64_t PacedSender::QueueInMs() const {
	CriticalSectionScoped cs(critsect_.get());

	int64_t oldest_packet = packets_->OldestEnqueueTime();
	if (oldest_packet == 0)
	return 0;

	return clock_->TimeInMilliseconds() - oldest_packet;
	}

	int64_t PacedSender::TimeUntilNextProcess() {
	CriticalSectionScoped cs(critsect_.get());
	if (prober_->IsProbing()) {
	int64_t ret = prober_->TimeUntilNextProbe(clock_->TimeInMilliseconds());
	if (ret >= 0) {
	return ret;
	}
	}
	int64_t elapsed_time_us = clock_->TimeInMicroseconds() - time_last_update_us_;
	int64_t elapsed_time_ms = (elapsed_time_us + 500) / 1000;
	return std::max<int64_t>(kMinPacketLimitMs - elapsed_time_ms, 0);
	}

	int32_t PacedSender::Process() {
	int64_t now_us = clock_->TimeInMicroseconds();
	CriticalSectionScoped cs(critsect_.get());
	int64_t elapsed_time_ms = (now_us - time_last_update_us_ + 500) / 1000;
	time_last_update_us_ = now_us;
	if (paused_)
	return 0;
	if (elapsed_time_ms > 0) {
	int64_t delta_time_ms = std::min(kMaxIntervalTimeMs, elapsed_time_ms);
	UpdateBytesPerInterval(delta_time_ms);
	}
	while (!packets_->Empty()) {
	if (media_budget_->bytes_remaining() == 0 && !prober_->IsProbing()) {
	return 0;
	}

	// Since we need to release the lock in order to send, we first pop the
	// element from the priority queue but keep it in storage, so that we can
	// reinsert it if send fails.
	const paced_sender::Packet& packet = packets_->BeginPop();
	if (SendPacket(packet)) {
	// Send succeeded, remove it from the queue.
	packets_->FinalizePop(packet);
	if (prober_->IsProbing()) {
	return 0;
	}
	} else {
	// Send failed, put it back into the queue.
	packets_->CancelPop(packet);
	return 0;
	}
	}

	if (!packets_->Empty())
	return 0;

	size_t padding_needed;
	if (prober_->IsProbing())
	padding_needed = prober_->RecommendedPacketSize();
	else
	padding_needed = padding_budget_->bytes_remaining();

	if (padding_needed > 0)
	SendPadding(static_cast<size_t>(padding_needed));
	return 0;
	}

	bool PacedSender::SendPacket(const paced_sender::Packet& packet) {
	critsect_->Leave();
	const bool success = callback_->TimeToSendPacket(packet.ssrc,
	packet.sequence_number,
	packet.capture_time_ms,
	packet.retransmission);
	critsect_->Enter();

	if (success) {
	// Update media bytes sent.
	prober_->PacketSent(clock_->TimeInMilliseconds(), packet.bytes);
	media_budget_->UseBudget(packet.bytes);
	padding_budget_->UseBudget(packet.bytes);
	}

	return success;
	}

	void PacedSender::SendPadding(size_t padding_needed) {
	critsect_->Leave();
	size_t bytes_sent = callback_->TimeToSendPadding(padding_needed);
	critsect_->Enter();

	if (bytes_sent > 0) {
	prober_->PacketSent(clock_->TimeInMilliseconds(), bytes_sent);
	media_budget_->UseBudget(bytes_sent);
	padding_budget_->UseBudget(bytes_sent);
	}
	}

	void PacedSender::UpdateBytesPerInterval(int64_t delta_time_ms) {
	media_budget_->IncreaseBudget(delta_time_ms);
	padding_budget_->IncreaseBudget(delta_time_ms);
	}
	} // namespace webrtc