Fill Level Low Pass Filter. More...

#include <filllevel.h>

Public Member Functions
void	Reset ()
	Resets the filter state.

void	ResetFramesCounters ()
	Resets the received and written frames counters.

int	GetFramesReceived ()

int	GetFramesPlayed ()

void	ReceivedFrames (int count)

void	WroteFrames (int count)

double	GetBufferFillLevelFramesAvg ()

void	SetMinBufferSizeFrames (int size)

void	UpdateAvgBufferFillLevel (int)
	Updates the buffer fill level average.

bool	IsSettled ()

Private Types
enum	State { UNINITIALIZED , SETTLING , SETTLED }

Private Member Functions
const char *	StateToString (State d)
	Converts the filter state to a string representation.

Private Attributes
std::mutex	m_mutex

State	m_state = UNINITIALIZED

int	m_receivedFrames = 0

int	m_writtenToAlsaFrames = 0

double	m_bufferFillLevelFramesAvg = 0

double	m_bufferFillLevelFramesTargetValue = 0

int	m_frameCounter = 0

double	m_floatingAverageAlpha = FLOATING_AVERAGE_ALPHA_NORMAL

int	m_minBufferSizeFrames = 0

Static Private Attributes
static constexpr double	FLOATING_AVERAGE_ALPHA_SETTLING = 0.02

static constexpr double	FLOATING_AVERAGE_ALPHA_NORMAL = 0.002

static constexpr int	SETTLING_DURATION_PACKETS = 30 / 0.16

Detailed Description

Fill Level Low Pass Filter.

Definition at line 20 of file filllevel.h.

Member Enumeration Documentation

◆ State

enum cBufferFillLevelLowPassFilter::State

private

Enumerator
UNINITIALIZED
SETTLING
SETTLED

Definition at line 34 of file filllevel.h.

Member Function Documentation

◆ GetBufferFillLevelFramesAvg()

double cBufferFillLevelLowPassFilter::GetBufferFillLevelFramesAvg ( )

inline

Definition at line 28 of file filllevel.h.

References m_bufferFillLevelFramesAvg, and m_mutex.

Referenced by cSoftHdAudio::ClockDriftCompensation().

◆ GetFramesPlayed()

int cBufferFillLevelLowPassFilter::GetFramesPlayed ( )

inline

Definition at line 25 of file filllevel.h.

References m_mutex, and m_writtenToAlsaFrames.

◆ GetFramesReceived()

int cBufferFillLevelLowPassFilter::GetFramesReceived ( )

inline

Definition at line 24 of file filllevel.h.

References m_mutex, and m_receivedFrames.

◆ IsSettled()

bool cBufferFillLevelLowPassFilter::IsSettled ( )

inline

Definition at line 31 of file filllevel.h.

References m_mutex, m_state, and SETTLED.

Referenced by cSoftHdAudio::ClockDriftCompensation().

◆ ReceivedFrames()

void cBufferFillLevelLowPassFilter::ReceivedFrames ( int count )

inline

Definition at line 26 of file filllevel.h.

References m_mutex, and m_receivedFrames.

Referenced by cSoftHdAudio::Enqueue().

◆ Reset()

void cBufferFillLevelLowPassFilter::Reset ( void )

Resets the filter state.

Definition at line 18 of file filllevel.cpp.

References m_bufferFillLevelFramesAvg, m_frameCounter, m_state, and UNINITIALIZED.

Referenced by cSoftHdAudio::DropSamplesOlderThanPtsMs(), and cSoftHdAudio::FlushBuffers().

◆ ResetFramesCounters()

void cBufferFillLevelLowPassFilter::ResetFramesCounters ( void )

Resets the received and written frames counters.

Definition at line 28 of file filllevel.cpp.

References m_receivedFrames, and m_writtenToAlsaFrames.

Referenced by cSoftHdAudio::FlushBuffers().

◆ SetMinBufferSizeFrames()

void cBufferFillLevelLowPassFilter::SetMinBufferSizeFrames ( int size )

inline

Definition at line 29 of file filllevel.h.

References m_minBufferSizeFrames, and m_mutex.

◆ StateToString()

const char * cBufferFillLevelLowPassFilter::StateToString ( State state )

private

Converts the filter state to a string representation.

Parameters

state The state to convert

Returns: String representation of the state

Definition at line 84 of file filllevel.cpp.

References SETTLED, SETTLING, and UNINITIALIZED.

◆ UpdateAvgBufferFillLevel()

void cBufferFillLevelLowPassFilter::UpdateAvgBufferFillLevel ( int hardwareBufferFillLevelFrames )

Updates the buffer fill level average.

Calculates the current buffer fill level based on received frames, written frames, and the hardware buffer fill level. Applies a low-pass filter (exponential moving average) to smooth the value. This is necessary, because the packets coming from VDR have a few milliseconds jitter.

Handles state transitions:

UNINITIALIZED -> SETTLING: Initializes the average and sets a faster alpha.
SETTLING -> SETTLED: After a duration, switches to a slower alpha and fixes the target value.

Parameters

hardwareBufferFillLevelFrames Current fill level reported by the hardware (ALSA)

Definition at line 48 of file filllevel.cpp.

References FLOATING_AVERAGE_ALPHA_NORMAL, FLOATING_AVERAGE_ALPHA_SETTLING, m_bufferFillLevelFramesAvg, m_bufferFillLevelFramesTargetValue, m_floatingAverageAlpha, m_frameCounter, m_minBufferSizeFrames, m_mutex, m_receivedFrames, m_state, m_writtenToAlsaFrames, SETTLED, SETTLING, SETTLING_DURATION_PACKETS, and UNINITIALIZED.