ts::TSSpeedMetrics Class Reference

TS processing speed metrics evaluation. More...

#include <tsTSSpeedMetrics.h>

Public Member Functions
	TSSpeedMetrics (PacketCounter packets=MIN_PACKET_PER_INTERVAL, cn::nanoseconds nanosecs=MIN_NANOSEC_PER_INTERVAL, size_t intervals=INTERVAL_COUNT)
	Constructor.
BitRate	bitrate () const
	Get the evaluated processing bitrate in bits/second based on 188-byte packets.
bool	processedPacket (PacketCounter count=1)
	Report the processing of some TS packets by the application.
cn::nanoseconds	sessionNanoSeconds () const
	Get the duration of the session, since start(), in nanoseconds.
void	start ()
	Start a new processing time session.

Static Public Attributes
static constexpr size_t	INTERVAL_COUNT = 20
	Default number of intervals in the sliding window of bitrate computation.
static constexpr cn::nanoseconds	MIN_NANOSEC_PER_INTERVAL = cn::milliseconds(100)
	Default minimum number of nanoseconds per interval.
static constexpr PacketCounter	MIN_PACKET_PER_INTERVAL = 100
	Default minimum packets to accumulate per interval.

Detailed Description

TS processing speed metrics evaluation.

An instance of this class evaluates the reading or processing speed of a TS. This is different from the TS bitrate, as evaluated by the class PCRAnalyzer, when the TS is not a live one but a file for instance.

This class is useful to perform actions at regular intervals, based on wall clock time, not TS clock. Instead of checking the system time at every packet, which is far from efficient, an application can predict an average number of packets to process before performing the repetitive action.

Warning: The processing speed of the TS is typically not stable. Buffer sizes impact the latency for instance. As well as any external factor in the operating system. So, predictions on packet distance are only hints at best. This class shall be considered as an optimization on the number of times the system time is probed, not a precise prediction.

Principle of operation:

• We work on a monotonic clock and we count packets.
• We compute an "current" processing bitrate, not an average bitrate from the beginning.
• The bitrate is computed over the last period of at least 2 seconds and at least 2000 packets (default values).
• This "current period" is in fact made of a sliding windows of 20 elementary interval. Each interval must extend over at least 100 packets and 100 milliseconds.

Constructor & Destructor Documentation

TSSpeedMetrics()

ts::TSSpeedMetrics::TSSpeedMetrics	(	PacketCounter	packets = MIN_PACKET_PER_INTERVAL,
		cn::nanoseconds	nanosecs = MIN_NANOSEC_PER_INTERVAL,
		size_t	intervals = INTERVAL_COUNT
	)

Constructor.

Parameters

[in]	packets	Minimum packets to accumulate per interval.
[in]	nanosecs	Minimum number of nanoseconds per interval.
[in]	intervals	Max number of sliding time intervals.

Member Function Documentation

processedPacket()

bool ts::TSSpeedMetrics::processedPacket

(

PacketCounter

count = 1

)

Report the processing of some TS packets by the application.

Parameters

[in]

count

Number of processed packets, one by default.

Returns

True if we just fetched the value of the clock.

bitrate()

BitRate ts::TSSpeedMetrics::bitrate

(

)

const

Get the evaluated processing bitrate in bits/second based on 188-byte packets.

Returns

The evaluated TS bitrate in bits/second or zero if not available.

sessionNanoSeconds()

cn::nanoseconds ts::TSSpeedMetrics::sessionNanoSeconds ( ) const

inline

Get the duration of the session, since start(), in nanoseconds.

The value is the most precise when processedPacket() just returned true.

Returns

The duration of the session, since start(), in nanoseconds.

Member Data Documentation

MIN_PACKET_PER_INTERVAL

constexpr PacketCounter ts::TSSpeedMetrics::MIN_PACKET_PER_INTERVAL = 100

staticconstexpr

Default minimum packets to accumulate per interval.

See the description of the class.

MIN_NANOSEC_PER_INTERVAL

constexpr cn::nanoseconds ts::TSSpeedMetrics::MIN_NANOSEC_PER_INTERVAL = cn::milliseconds(100)

staticconstexpr

Default minimum number of nanoseconds per interval.

See the description of the class.

INTERVAL_COUNT

constexpr size_t ts::TSSpeedMetrics::INTERVAL_COUNT = 20

staticconstexpr

Default number of intervals in the sliding window of bitrate computation.

See the description of the class.

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

• tsTSSpeedMetrics.h