Stroboscope Class Reference

Class for a stroboscopic tuning indicator. More...

#include <stroboscope.h>

Collaboration diagram for Stroboscope:

Public Types
using	Complex = std::complex< double >
	Type for a complex number. More...
using	ComplexVector = std::vector< Complex >
	Type for a vector of complex numbers. More...

Public Member Functions
	Stroboscope (AudioRecorderAdapter *recorder)
	Constructor. More...
void	start ()
	Start the stroboscope. More...
void	stop ()
	Stop the stroboscope. More...
void	setFramesPerSecond (double fps)
	Stroboscope::setFramesPerSecond. More...
void	setFrequencies (const std::vector< double > &frequencies)
	Stroboscope::setFrequencies. More...
void	pushRawData (const AudioBase::PacketType &data)
	Stroboscope::pushRawData. More...

Private Attributes
const double	AMPLITUDE_DAMPING = 0.95
	Damping factor of the normalizing amplitude level on a single frame (0...1) More...
const double	FRAME_DAMPING = 0.5
	Damping of the complex phases from frame to frame (0...1) More...
AudioRecorderAdapter *	mRecorder
	Pointer to the audio recorder. More...
bool	mActive
	Flag indicating activity (start/stop) More...
int	mSamplesPerFrame
	Number of PCM samples per frame. More...
int	mSampleCounter
	Actual number of PCM samples read. More...
double	mMaxAmplitude
	Sliding amplitude to normalize the data. More...
ComplexVector	mComplexPhase
	Rotating complex number. More...
ComplexVector	mComplexIncrement
	Factor by which the complex number rotates. More...
ComplexVector	mMeanComplexPhase
	Phase average over the actual frame. More...
std::mutex	mMutex
	Mutex protecting access from different threads. More...

Detailed Description

Class for a stroboscopic tuning indicator.

Ordinary stroboscopic tuners show the analog audio signal amplitude in terms of light intensity masked by a rotating disk. See e.g. https://en.wikipedia.org/wiki/Electronic_tuner#How_a_strobe_tuner_works

Doing the same in our software would require to send the complete PCM data to a stroboscopic drawer which would display it in real time pixel by pixel. This would be computationally expensive. Moreover, the messaging sytem would not be suitable for such a data stream.

We therefore choose a different method. The AudioRecorderAdapter holds an instance of this class and calls the function pushRawData (see below), transmitting all PCM data. This data is reorganized in packages of the size mSamplesPerFrame. Each frame is convolved with a complex number rotating on its unit circle. The speed at which the complex number rotates corresponds to the expected frequencies of the partials, as specified by the function set Frequencies. The result is a set of complex numbers (one for each partial), encoding the intensity of the partial and its complex phase shift. This data is sent (only once for each frame) via the messaging system.

The TuningIndicatorDrawer listens to these messages and draws horizontal bars with phase-shifted rainbow colors.

See also

AudioRecorderAdapter

TuningIndicatorDrawer

Definition at line 67 of file stroboscope.h.

Member Typedef Documentation

using Stroboscope::Complex = std::complex<double>

Type for a complex number.

Definition at line 77 of file stroboscope.h.

using Stroboscope::ComplexVector = std::vector<Complex>

Type for a vector of complex numbers.

Definition at line 78 of file stroboscope.h.

Constructor & Destructor Documentation

Stroboscope::Stroboscope

(

AudioRecorderAdapter *

recorder

)

Constructor.

Stroboscope::Stroboscope.

Parameters

recorder

Definition at line 40 of file stroboscope.cpp.

Member Function Documentation

void Stroboscope::pushRawData

(

const AudioBase::PacketType &

data

)

Stroboscope::pushRawData.

Parameters

data

Definition at line 59 of file stroboscope.cpp.

Here is the call graph for this function:

void Stroboscope::setFramesPerSecond

(

double

fps

)

Stroboscope::setFramesPerSecond.

Parameters

fps

Definition at line 101 of file stroboscope.cpp.

Here is the call graph for this function:

void Stroboscope::setFrequencies

(

const std::vector< double > &

frequencies

)

Stroboscope::setFrequencies.

Parameters

frequencies

Definition at line 116 of file stroboscope.cpp.

Here is the call graph for this function:

void Stroboscope::start ( )

inline

Start the stroboscope.

Definition at line 81 of file stroboscope.h.

void Stroboscope::stop ( )

inline

Stop the stroboscope.

Definition at line 82 of file stroboscope.h.

Member Data Documentation

const double Stroboscope::AMPLITUDE_DAMPING = 0.95

private

Damping factor of the normalizing amplitude level on a single frame (0...1)

Definition at line 71 of file stroboscope.h.

const double Stroboscope::FRAME_DAMPING = 0.5

private

Damping of the complex phases from frame to frame (0...1)

Definition at line 74 of file stroboscope.h.

bool Stroboscope::mActive

private

Flag indicating activity (start/stop)

Definition at line 90 of file stroboscope.h.

ComplexVector Stroboscope::mComplexIncrement

private

Factor by which the complex number rotates.

Definition at line 95 of file stroboscope.h.

ComplexVector Stroboscope::mComplexPhase

private

Rotating complex number.

Definition at line 94 of file stroboscope.h.

double Stroboscope::mMaxAmplitude

private

Sliding amplitude to normalize the data.

Definition at line 93 of file stroboscope.h.

ComplexVector Stroboscope::mMeanComplexPhase

private

Phase average over the actual frame.

Definition at line 96 of file stroboscope.h.

std::mutex Stroboscope::mMutex

private

Mutex protecting access from different threads.

Definition at line 97 of file stroboscope.h.

AudioRecorderAdapter* Stroboscope::mRecorder

private

Pointer to the audio recorder.

Definition at line 89 of file stroboscope.h.

int Stroboscope::mSampleCounter

private

Actual number of PCM samples read.

Definition at line 92 of file stroboscope.h.

int Stroboscope::mSamplesPerFrame

private

Number of PCM samples per frame.

Definition at line 91 of file stroboscope.h.

---

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

• /home/hinrichsen/Dokumente/Aktuell/EPT/Entropy-Piano-Tuner/core/audio/recorder/stroboscope.h
• /home/hinrichsen/Dokumente/Aktuell/EPT/Entropy-Piano-Tuner/core/audio/recorder/stroboscope.cpp