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* Copyright (c) 2013 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 <memory>
#include "api/neteq/neteq.h"
#include "api/neteq/neteq_controller.h"
#include "api/neteq/tick_timer.h"
#include "modules/audio_coding/neteq/buffer_level_filter.h"
#include "modules/audio_coding/neteq/delay_manager.h"
#include "rtc_base/constructor_magic.h"
#include "rtc_base/experiments/field_trial_parser.h"
namespace webrtc {
// This is the class for the decision tree implementation.
class DecisionLogic : public NetEqController {
static const int kReinitAfterExpands = 100;
static const int kMaxWaitForPacket = 10;
// Constructor.
DecisionLogic(NetEqController::Config config);
DecisionLogic(NetEqController::Config config,
std::unique_ptr<DelayManager> delay_manager,
std::unique_ptr<BufferLevelFilter> buffer_level_filter);
~DecisionLogic() override;
// Resets object to a clean state.
void Reset() override;
// Resets parts of the state. Typically done when switching codecs.
void SoftReset() override;
// Sets the sample rate and the output block size.
void SetSampleRate(int fs_hz, size_t output_size_samples) override;
// Given info about the latest received packet, and current jitter buffer
// status, returns the operation. `target_timestamp` and `expand_mutefactor`
// are provided for reference. `last_packet_samples` is the number of samples
// obtained from the last decoded frame. If there is a packet available, it
// should be supplied in `packet`; otherwise it should be NULL. The mode
// resulting from the last call to NetEqImpl::GetAudio is supplied in
// `last_mode`. If there is a DTMF event to play, `play_dtmf` should be set to
// true. The output variable `reset_decoder` will be set to true if a reset is
// required; otherwise it is left unchanged (i.e., it can remain true if it
// was true before the call).
NetEq::Operation GetDecision(const NetEqController::NetEqStatus& status,
bool* reset_decoder) override;
// These methods test the `cng_state_` for different conditions.
bool CngRfc3389On() const override { return cng_state_ == kCngRfc3389On; }
bool CngOff() const override { return cng_state_ == kCngOff; }
// Resets the `cng_state_` to kCngOff.
void SetCngOff() override { cng_state_ = kCngOff; }
// Reports back to DecisionLogic whether the decision to do expand remains or
// not. Note that this is necessary, since an expand decision can be changed
// to kNormal in NetEqImpl::GetDecision if there is still enough data in the
// sync buffer.
void ExpandDecision(NetEq::Operation operation) override;
// Adds `value` to `sample_memory_`.
void AddSampleMemory(int32_t value) override { sample_memory_ += value; }
int TargetLevelMs() const override { return delay_manager_->TargetDelayMs(); }
absl::optional<int> PacketArrived(int fs_hz,
bool should_update_stats,
const PacketArrivedInfo& info) override;
void RegisterEmptyPacket() override {}
void NotifyMutedState() override {}
bool SetMaximumDelay(int delay_ms) override {
return delay_manager_->SetMaximumDelay(delay_ms);
bool SetMinimumDelay(int delay_ms) override {
return delay_manager_->SetMinimumDelay(delay_ms);
bool SetBaseMinimumDelay(int delay_ms) override {
return delay_manager_->SetBaseMinimumDelay(delay_ms);
int GetBaseMinimumDelay() const override {
return delay_manager_->GetBaseMinimumDelay();
bool PeakFound() const override { return false; }
int GetFilteredBufferLevel() const override {
return buffer_level_filter_->filtered_current_level();
// Accessors and mutators.
void set_sample_memory(int32_t value) override { sample_memory_ = value; }
size_t noise_fast_forward() const override { return noise_fast_forward_; }
size_t packet_length_samples() const override {
return packet_length_samples_;
void set_packet_length_samples(size_t value) override {
packet_length_samples_ = value;
void set_prev_time_scale(bool value) override { prev_time_scale_ = value; }
// The value 5 sets maximum time-stretch rate to about 100 ms/s.
static const int kMinTimescaleInterval = 5;
enum CngState { kCngOff, kCngRfc3389On, kCngInternalOn };
// Updates the `buffer_level_filter_` with the current buffer level
// `buffer_size_samples`.
void FilterBufferLevel(size_t buffer_size_samples);
// Returns the operation given that the next available packet is a comfort
// noise payload (RFC 3389 only, not codec-internal).
virtual NetEq::Operation CngOperation(NetEq::Mode prev_mode,
uint32_t target_timestamp,
uint32_t available_timestamp,
size_t generated_noise_samples);
// Returns the operation given that no packets are available (except maybe
// a DTMF event, flagged by setting `play_dtmf` true).
virtual NetEq::Operation NoPacket(bool play_dtmf);
// Returns the operation to do given that the expected packet is available.
virtual NetEq::Operation ExpectedPacketAvailable(NetEq::Mode prev_mode,
bool play_dtmf);
// Returns the operation to do given that the expected packet is not
// available, but a packet further into the future is at hand.
virtual NetEq::Operation FuturePacketAvailable(
size_t decoder_frame_length,
NetEq::Mode prev_mode,
uint32_t target_timestamp,
uint32_t available_timestamp,
bool play_dtmf,
size_t generated_noise_samples,
size_t span_samples_in_packet_buffer,
size_t num_packets_in_packet_buffer);
// Checks if enough time has elapsed since the last successful timescale
// operation was done (i.e., accelerate or preemptive expand).
bool TimescaleAllowed() const {
return !timescale_countdown_ || timescale_countdown_->Finished();
// Checks if the current (filtered) buffer level is under the target level.
bool UnderTargetLevel() const;
// Checks if `timestamp_leap` is so long into the future that a reset due
// to exceeding kReinitAfterExpands will be done.
bool ReinitAfterExpands(uint32_t timestamp_leap) const;
// Checks if we still have not done enough expands to cover the distance from
// the last decoded packet to the next available packet, the distance beeing
// conveyed in `timestamp_leap`.
bool PacketTooEarly(uint32_t timestamp_leap) const;
// Checks if num_consecutive_expands_ >= kMaxWaitForPacket.
bool MaxWaitForPacket() const;
std::unique_ptr<DelayManager> delay_manager_;
std::unique_ptr<BufferLevelFilter> buffer_level_filter_;
const TickTimer* tick_timer_;
int sample_rate_;
size_t output_size_samples_;
CngState cng_state_ = kCngOff; // Remember if comfort noise is interrupted by
// other event (e.g., DTMF).
size_t noise_fast_forward_ = 0;
size_t packet_length_samples_ = 0;
int sample_memory_ = 0;
bool prev_time_scale_ = false;
bool disallow_time_stretching_;
std::unique_ptr<TickTimer::Countdown> timescale_countdown_;
int num_consecutive_expands_ = 0;
int time_stretched_cn_samples_ = 0;
bool last_pack_cng_or_dtmf_ = true;
bool buffer_flush_ = false;
FieldTrialParameter<bool> estimate_dtx_delay_;
FieldTrialParameter<bool> time_stretch_cn_;
FieldTrialConstrained<int> target_level_window_ms_;
} // namespace webrtc