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* 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 <deque>
#include <map>
#include <memory>
#include <set>
#include <vector>
#include "api/function_view.h"
#include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
#include "rtc_base/constructor_magic.h"
#include "rtc_base/critical_section.h"
#include "rtc_base/thread_annotations.h"
namespace webrtc {
class Clock;
class RtpPacketToSend;
class RtpPacketHistory {
enum class StorageMode {
kDisabled, // Don't store any packets.
kStoreAndCull // Store up to |number_to_store| packets, but try to remove
// packets as they time out or as signaled as received.
// Snapshot indicating the state of a packet in the history.
struct PacketState {
PacketState(const PacketState&);
uint16_t rtp_sequence_number = 0;
absl::optional<int64_t> send_time_ms;
int64_t capture_time_ms = 0;
uint32_t ssrc = 0;
size_t packet_size = 0;
// Number of times RE-transmitted, ie not including the first transmission.
size_t times_retransmitted = 0;
bool pending_transmission = false;
// Maximum number of packets we ever allow in the history.
static constexpr size_t kMaxCapacity = 9600;
// Maximum number of entries in prioritized queue of padding packets.
static constexpr size_t kMaxPaddingtHistory = 63;
// Don't remove packets within max(1000ms, 3x RTT).
static constexpr int64_t kMinPacketDurationMs = 1000;
static constexpr int kMinPacketDurationRtt = 3;
// With kStoreAndCull, always remove packets after 3x max(1000ms, 3x rtt).
static constexpr int kPacketCullingDelayFactor = 3;
RtpPacketHistory(Clock* clock, bool enable_padding_prio);
// Set/get storage mode. Note that setting the state will clear the history,
// even if setting the same state as is currently used.
void SetStorePacketsStatus(StorageMode mode, size_t number_to_store);
StorageMode GetStorageMode() const;
// Set RTT, used to avoid premature retransmission and to prevent over-writing
// a packet in the history before we are reasonably sure it has been received.
void SetRtt(int64_t rtt_ms);
// If |send_time| is set, packet was sent without using pacer, so state will
// be set accordingly.
void PutRtpPacket(std::unique_ptr<RtpPacketToSend> packet,
absl::optional<int64_t> send_time_ms);
// Gets stored RTP packet corresponding to the input |sequence number|.
// Returns nullptr if packet is not found or was (re)sent too recently.
std::unique_ptr<RtpPacketToSend> GetPacketAndSetSendTime(
uint16_t sequence_number);
// Gets stored RTP packet corresponding to the input |sequence number|.
// Returns nullptr if packet is not found or was (re)sent too recently.
// If a packet copy is returned, it will be marked as pending transmission but
// does not update send time, that must be done by MarkPacketAsSent().
std::unique_ptr<RtpPacketToSend> GetPacketAndMarkAsPending(
uint16_t sequence_number);
// In addition to getting packet and marking as sent, this method takes an
// encapsulator function that takes a reference to the packet and outputs a
// copy that may be wrapped in a container, eg RTX.
// If the the encapsulator returns nullptr, the retransmit is aborted and the
// packet will not be marked as pending.
std::unique_ptr<RtpPacketToSend> GetPacketAndMarkAsPending(
uint16_t sequence_number,
const RtpPacketToSend&)> encapsulate);
// Updates the send time for the given packet and increments the transmission
// counter. Marks the packet as no longer being in the pacer queue.
void MarkPacketAsSent(uint16_t sequence_number);
// Similar to GetPacketAndSetSendTime(), but only returns a snapshot of the
// current state for packet, and never updates internal state.
absl::optional<PacketState> GetPacketState(uint16_t sequence_number) const;
// Get the packet (if any) from the history, that is deemed most likely to
// the remote side. This is calculated from heuristics such as packet age
// and times retransmitted. Updated the send time of the packet, so is not
// a const method.
std::unique_ptr<RtpPacketToSend> GetPayloadPaddingPacket();
// Same as GetPayloadPaddingPacket(void), but adds an encapsulation
// that can be used for instance to encapsulate the packet in an RTX
// container, or to abort getting the packet if the function returns
// nullptr.
std::unique_ptr<RtpPacketToSend> GetPayloadPaddingPacket(
const RtpPacketToSend&)> encapsulate);
// Cull packets that have been acknowledged as received by the remote end.
void CullAcknowledgedPackets(rtc::ArrayView<const uint16_t> sequence_numbers);
// Mark packet as queued for transmission. This will prevent premature
// removal or duplicate retransmissions in the pacer queue.
// Returns true if status was set, false if packet was not found.
bool SetPendingTransmission(uint16_t sequence_number);
// Remove all pending packets from the history, but keep storage mode and
// capacity.
void Clear();
struct MoreUseful;
class StoredPacket;
using PacketPrioritySet = std::set<StoredPacket*, MoreUseful>;
class StoredPacket {
StoredPacket(std::unique_ptr<RtpPacketToSend> packet,
absl::optional<int64_t> send_time_ms,
uint64_t insert_order);
StoredPacket& operator=(StoredPacket&&);
uint64_t insert_order() const { return insert_order_; }
size_t times_retransmitted() const { return times_retransmitted_; }
void IncrementTimesRetransmitted(PacketPrioritySet* priority_set);
// The time of last transmission, including retransmissions.
absl::optional<int64_t> send_time_ms_;
// The actual packet.
std::unique_ptr<RtpPacketToSend> packet_;
// True if the packet is currently in the pacer queue pending transmission.
bool pending_transmission_;
// Unique number per StoredPacket, incremented by one for each added
// packet. Used to sort on insert order.
uint64_t insert_order_;
// Number of times RE-transmitted, ie excluding the first transmission.
size_t times_retransmitted_;
struct MoreUseful {
bool operator()(StoredPacket* lhs, StoredPacket* rhs) const;
// Helper method used by GetPacketAndSetSendTime() and GetPacketState() to
// check if packet has too recently been sent.
bool VerifyRtt(const StoredPacket& packet, int64_t now_ms) const
void CullOldPackets(int64_t now_ms) RTC_EXCLUSIVE_LOCKS_REQUIRED(lock_);
// Removes the packet from the history, and context/mapping that has been
// stored. Returns the RTP packet instance contained within the StoredPacket.
std::unique_ptr<RtpPacketToSend> RemovePacket(int packet_index)
int GetPacketIndex(uint16_t sequence_number) const
StoredPacket* GetStoredPacket(uint16_t sequence_number)
static PacketState StoredPacketToPacketState(
const StoredPacket& stored_packet);
Clock* const clock_;
const bool enable_padding_prio_;
rtc::CriticalSection lock_;
size_t number_to_store_ RTC_GUARDED_BY(lock_);
StorageMode mode_ RTC_GUARDED_BY(lock_);
int64_t rtt_ms_ RTC_GUARDED_BY(lock_);
// Queue of stored packets, ordered by sequence number, with older packets in
// the front and new packets being added to the back. Note that there may be
// wrap-arounds so the back may have a lower sequence number.
// Packets may also be removed out-of-order, in which case there will be
// instances of StoredPacket with |packet_| set to nullptr. The first and last
// entry in the queue will however always be populated.
std::deque<StoredPacket> packet_history_ RTC_GUARDED_BY(lock_);
// Total number of packets with inserted.
uint64_t packets_inserted_ RTC_GUARDED_BY(lock_);
// Objects from |packet_history_| ordered by "most likely to be useful", used
// in GetPayloadPaddingPacket().
PacketPrioritySet padding_priority_ RTC_GUARDED_BY(lock_);
} // namespace webrtc