roc::audio::LatencyMonitor Class Reference

Latency monitor. More...

#include <latency_monitor.h>

Inheritance diagram for roc::audio::LatencyMonitor:

Collaboration diagram for roc::audio::LatencyMonitor:

Public Member Functions
	LatencyMonitor (IFrameReader &frame_reader, const packet::SortedQueue &incoming_queue, const Depacketizer &depacketizer, const packet::ILinkMeter &link_meter, ResamplerReader *resampler, const LatencyConfig &config, const SampleSpec &packet_sample_spec, const SampleSpec &frame_sample_spec)
	Constructor. More...
bool	is_valid () const
	Check if the object was initialized successfully. More...
bool	is_alive () const
	Check if the stream is still alive. More...
const LatencyMetrics &	metrics () const
	Get metrics. More...
virtual bool	read (Frame &frame)
	Read audio frame from a pipeline. More...
bool	reclock (core::nanoseconds_t playback_timestamp)
	Report playback timestamp of last frame returned by read. More...
Public Member Functions inherited from roc::core::ListNode< Tag >
ListData *	list_data () const
	Get pointer to internal data. More...

Additional Inherited Members
Static Public Member Functions inherited from roc::core::ListNode< Tag >
static ListNode *	list_node (ListData *data)
	Get pointer to parent node from pointer to internal data. More...

Detailed Description

Latency monitor.

Features

• calculates NIQ latency (network incoming queue) - how many samples are buffered in receiver packet queue and receiver pipeline before depacketizer
• calculates E2E latency (end-to-end) - how much time passed between frame was captured on sender and played on receiver (this is based on capture timestamps, which are populated with the help of RTCP)
• asks LatencyTuner to calculate scaling factor based on the actual and target latencies
• passes calculated scaling factor to resampler

Flow

• pipeline periodically calls read() method; it uses references to incoming packet queue (start of the pipeline) and depacketizer (last pipeline element that works with packets), asks them about current packet / frame, and calculates distance between them, which is NIQ latency
• after adding frame to playback buffer, pipeline invokes reclock() method; it calculates difference between capture and playback time of the frame, which is E2E latency
• latency monitor has an instance of LatencyTuner; it continuously passes calculated latencies to it, and obtains scaling factor for resampler
• latency monitor has a reference to resampler, and periodically passes updated scaling factor to it
• pipeline also can query latency monitor for latency metrics on behalf of request from user or to report them to sender via RTCP

Definition at line 60 of file latency_monitor.h.

Constructor & Destructor Documentation

LatencyMonitor()

roc::audio::LatencyMonitor::LatencyMonitor	(	IFrameReader &	frame_reader,
		const packet::SortedQueue &	incoming_queue,
		const Depacketizer &	depacketizer,
		const packet::ILinkMeter &	link_meter,
		ResamplerReader *	resampler,
		const LatencyConfig &	config,
		const SampleSpec &	packet_sample_spec,
		const SampleSpec &	frame_sample_spec
	)

Constructor.

Member Function Documentation

is_alive()

bool roc::audio::LatencyMonitor::is_alive

(

)

const

Check if the stream is still alive.

is_valid()

bool roc::audio::LatencyMonitor::is_valid

(

)

const

Check if the object was initialized successfully.

metrics()

const LatencyMetrics& roc::audio::LatencyMonitor::metrics

(

)

const

Get metrics.

read()

virtual bool roc::audio::LatencyMonitor::read ( Frame &  frame )

virtual

Read audio frame from a pipeline.

Remarks

Forwards frame from underlying reader as-is.

Implements roc::audio::IFrameReader.

reclock()

bool roc::audio::LatencyMonitor::reclock

(

core::nanoseconds_t

playback_timestamp

)

Report playback timestamp of last frame returned by read.

Remarks

Pipeline invokes this method after adding last frame to playback buffer and knowing its playback time.

Returns

false if the session is ended

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The documentation for this class was generated from the following file:

• roc_audio/latency_monitor.h