AudioStream implementation that processes audio data through Goertzel algorithm. This class acts as a passthrough filter that can detect specific frequencies in the audio stream. More...

#include <GoerzelStream.h>

Inheritance diagram for GoertzelStream:

Public Member Functions
virtual void	addNotifyAudioChange (AudioInfoSupport &bi)
	Adds target to be notified about audio changes.

virtual AudioInfo	audioInfo () override
	provides the actual input AudioInfo

virtual AudioInfo	audioInfoOut ()

virtual int	available () override

virtual int	availableForWrite () override

bool	begin ()
	Initialize detectors for all channels.

bool	begin (const GoertzelConfig &config)
	Initialize with GoertzelConfig.

virtual void	clearNotifyAudioChange ()
	Deletes all change notify subscriptions.

virtual void	end ()

virtual void	flush () override

const GoertzelConfig &	getConfig () const
	Get the current configuration.

float	getCurrentMagnitude (int channel=0)
	Get the current magnitude for frequency detection.

bool	isFrequencyDetected (int channel=0)
	Check if frequency is currently detected.

bool	isNotifyActive ()
	Checks if the automatic AudioInfo update is active.

virtual	operator bool ()

size_t	readBytes (uint8_t *data, size_t len) override
	Read data from input stream and process it.

virtual size_t	readSilence (uint8_t *buffer, size_t length)
	Source to generate silence: just sets the buffer to 0.

virtual bool	removeNotifyAudioChange (AudioInfoSupport &bi)
	Removes a target in order not to be notified about audio changes.

void	setAudioInfo (AudioInfo info) override
	Set audio format and initialize detector array.

void	setChannelDetectionCallback (void(callback)(int channel, float frequency, float magnitude, void ref))
	Set detection callback function for channel-aware frequency detection.

void	setNotifyActive (bool flag)
	Deactivate/Reactivate automatic AudioInfo updates: (default is active)

void	setOutput (Print &out)
	Defines/Changes the output target.

void	setReference (void *ref)
	Set reference pointer for callback context.

void	setStream (Stream &in)
	Defines/Changes the input & output.

void	setWriteBufferSize (int size)

size_t	write (const uint8_t *data, size_t len) override
	Process audio data and pass it through.

virtual size_t	write (uint8_t ch) override

virtual void	writeSilence (size_t len)
	Writes len bytes of silence (=0).

Protected Member Functions
void	checkDetection (int channel)
	Helper method to check detection and call callback.

float	clip (float value)
	Clip audio values to prevent overflow.

virtual int	not_supported (int out, const char *msg="")

void	notifyAudioChange (AudioInfo info)

void	processSamples (const uint8_t *data, size_t data_len)
	Generic sample processing method for both write and readBytes.

template<typename T >
void	processSamplesOfType (const uint8_t *data, size_t data_len, int channels)
	Template helper to process samples of a specific type.

void	refillReadBuffer ()

Protected Attributes
int	_timeout = 10

void(*	channel_detection_callback )(int channel, float frequency, float magnitude, void *ref) = nullptr
	User callback for detection events.

Vector< GoertzelDetector >	detectors
	One detector per audio channel.

AudioInfo	info

bool	is_notify_active = true

Vector< AudioInfoSupport * >	notify_vector

Print *	p_print = nullptr
	Output stream for writing audio data.

Stream *	p_stream = nullptr
	Input stream for reading audio data.

void *	ref = this
	User-defined reference for callback context.

GoertzelConfig	single_config
	Current algorithm configuration.

RingBuffer< uint8_t >	tmp_in {0}

RingBuffer< uint8_t >	tmp_out {0}

int	write_buffer_size = MAX_SINGLE_CHARS

Detailed Description

AudioStream implementation that processes audio data through Goertzel algorithm. This class acts as a passthrough filter that can detect specific frequencies in the audio stream.

Supports multiple channels with independent frequency detection per channel. The number of detectors is determined by the channels field in GoertzelConfig.

Supports multiple sample formats:

8-bit: unsigned samples (0-255), converted to signed (-128 to 127)
16-bit: signed samples (-32768 to 32767)
24-bit: signed samples stored as 4 bytes, little-endian
32-bit: signed samples (-2147483648 to 2147483647)

Use this class in combination with a MultiStream to detect multiple frequencies.

Author: pschatzmann

Copyright: GPLv3

Member Function Documentation

◆ addNotifyAudioChange()

virtual void addNotifyAudioChange ( AudioInfoSupport & bi )

inlinevirtualinherited

Adds target to be notified about audio changes.

Reimplemented in CodecNOP, EncodedAudioOutput, EncodedAudioStream, AACDecoderFDK, DecoderBasic, MP3DecoderHelix, MP3DecoderMAD, OggContainerDecoder, Pipeline, and Pipeline::ModifyingStreamAdapter.

◆ audioInfo()

virtual AudioInfo audioInfo ( )

inlineoverridevirtualinherited

provides the actual input AudioInfo

Implements AudioInfoSupport.

Reimplemented in JupyterAudioT< T >, MozziStream, TimerCallbackAudioStream, PureDataStream, AdapterAudioOutputToAudioStream, GeneratedSoundStream< T >, GeneratedSoundStream< int16_t >, and InputMerge< T >.

◆ audioInfoOut()

virtual AudioInfo audioInfoOut ( )

inlinevirtualinherited

provides the actual output AudioInfo: this is usually the same as audioInfo() unless we use a transforming stream

Reimplemented in PureDataStream, PWMAudioOutput, ChannelFormatConverterStreamT< T >, ChannelFormatConverterStream, NumberFormatConverterStreamT< TFrom, TTo >, NumberFormatConverterStream, FormatConverterStream, Pipeline, ResampleStream, and ResampleStreamT< TInterpolator >.

◆ available()

virtual int available ( )

inlineoverridevirtualinherited

◆ availableForWrite()

virtual int availableForWrite ( )

inlineoverridevirtualinherited

Reimplemented from Print.

Reimplemented in UDPStream, A2DPStream, AudioFFTBase, I2SCodecStream, Equalizer3Bands, Equalizer3BandsPerChannel, AbstractURLStream, URLStreamESP32, I2SStream, MeasuringStream, ProgressStream, FrequencyDetectorAutoCorrelation, FrequencyDetectorZeroCrossing, and VolumeStream.

◆ begin() [1/2]

bool begin ( )

inlinevirtual

Initialize detectors for all channels.

Creates and configures individual Goertzel detectors for each audio channel. Each detector will independently analyze its channel for the target frequency.

Returns: true if at least one channel is configured, false otherwise

Reimplemented from BaseStream.

◆ begin() [2/2]

bool begin ( const GoertzelConfig & config )

inline

Initialize with GoertzelConfig.

Sets up the stream with specific Goertzel algorithm parameters. This method configures the audio format and detection parameters in one call.

Parameters

config Configuration object containing all parameters

Returns: true if initialization successful, false otherwise

◆ checkDetection()

void checkDetection ( int channel )

inlineprotected

Helper method to check detection and call callback.

Examines the magnitude from a detector and triggers the user callback if the magnitude exceeds the configured threshold. This method is called after each complete block is processed.

Parameters

channel Channel index that completed a detection block

◆ clip()

float clip ( float value )

inlineprotected

Clip audio values to prevent overflow.

Ensures that normalized audio samples stay within the valid range of [-1.0, 1.0] to prevent algorithm instability.

Parameters

value Input audio sample value

Returns: Clipped value in range [-1.0, 1.0]

◆ end()

virtual void end ( )

inlinevirtualinherited

◆ flush()

virtual void flush ( )

inlineoverridevirtualinherited

Reimplemented from Print.

Reimplemented in ResampleStream, BufferedTaskStream, and BufferedStream.

◆ getConfig()

const GoertzelConfig & getConfig ( ) const

inline

Get the current configuration.

Returns a reference to the current Goertzel configuration, including audio format, detection parameters, and processing settings.

Returns: Reference to the current GoertzelConfig

◆ getCurrentMagnitude()

float getCurrentMagnitude ( int channel = 0 )

inline

Get the current magnitude for frequency detection.

Returns the most recent magnitude calculation for the specified channel. The magnitude represents the strength of the target frequency in the last processed block of samples.

Parameters

channel Channel index (0-based, default: 0 for mono)

Returns: Magnitude value (0.0 if channel invalid or no detection)

◆ isFrequencyDetected()

bool isFrequencyDetected ( int channel = 0 )

inline

Check if frequency is currently detected.

Compares the current magnitude against the configured threshold to determine if the target frequency is present on the specified channel.

Parameters

channel Channel index (0-based, default: 0 for mono)

Returns: true if frequency detected above threshold, false otherwise

◆ operator bool()

virtual operator bool ( )

inlinevirtualinherited

Reimplemented in A2DPStream, I2SStream, MemoryStream, and Pipeline.

◆ processSamples()

void processSamples	(	const uint8_t *	data,
		size_t	data_len
	)

inlineprotected

Generic sample processing method for both write and readBytes.

This method serves as the central dispatcher for audio sample processing. It examines the configured sample format and routes the data to the appropriate type-specific processing method. This approach eliminates code duplication between write() and readBytes() methods.

Supported formats:

8-bit: Unsigned samples (0-255)
16-bit: Signed samples (-32768 to 32767)
24-bit: Signed samples in 3-byte packed format
32-bit: Signed samples (-2^31 to 2^31-1)

Parameters

data	Raw audio data buffer
data_len	Length of data buffer in bytes

◆ processSamplesOfType()

template<typename T >

void processSamplesOfType	(	const uint8_t *	data,
		size_t	data_len,
		int	channels
	)

inlineprotected

Template helper to process samples of a specific type.

Converts audio samples from their native format to normalized floats, applies volume scaling, and feeds them to the appropriate channel detectors. This method handles the format conversion and channel distribution automatically.

Template Parameters

T	Sample data type (uint8_t, int16_t, int24_t, int32_t)

Parameters

data	Raw audio data buffer
data_len	Length of data buffer in bytes
channels	Number of audio channels (for sample distribution)

◆ readBytes()

size_t readBytes	(	uint8_t *	data,
		size_t	len
	)

inlineoverridevirtual

Read data from input stream and process it.

Reads audio data from the input stream, processes it through the Goertzel detectors for frequency analysis, and returns the data to the caller. This allows for frequency detection in pull-mode audio processing.

Parameters

data	Output buffer to store read data
len	Maximum number of bytes to read

Returns: Number of bytes actually read

Reimplemented from AudioStream.

◆ setAudioInfo()

void setAudioInfo ( AudioInfo info )

inlineoverridevirtual

Set audio format and initialize detector array.

This method is called when the audio format changes. It updates the internal configuration and resizes the detector array to match the number of audio channels.

Parameters

info	Audio format information (sample rate, channels, bits per sample)

Reimplemented from AudioStream.

◆ setChannelDetectionCallback()

void setChannelDetectionCallback ( void(*)(int channel, float frequency, float magnitude, void *ref) callback )

inline

Set detection callback function for channel-aware frequency detection.

Registers a callback function that will be called when the target frequency is detected on any channel. The callback receives the channel number, detected frequency, magnitude, and a user reference pointer.

Parameters

callback Function to call when frequency is detected, includes channel info

◆ setReference()

void setReference ( void * ref )

inline

Set reference pointer for callback context.

Defines a reference to any object that should be available in the detection callback. This allows the callback to access application context or other objects.

Parameters

ref	Pointer to user-defined context object

◆ write() [1/2]

size_t write	(	const uint8_t *	data,
		size_t	len
	)

inlineoverridevirtual

Process audio data and pass it through.

This method receives audio data, processes it through the Goertzel detectors for frequency analysis, and then passes the unmodified data to the output stream. This allows for real-time frequency detection without affecting the audio flow.

Parameters

data	Input audio data buffer
len	Length of data in bytes

Returns: Number of bytes written to output stream

If there is no output stream, we just return the length

Reimplemented from AudioStream.

◆ write() [2/2]

virtual size_t write ( uint8_t ch )

inlineoverridevirtualinherited

Reimplemented in BufferedTaskStream, and BufferedStream.

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

src/AudioTools/CoreAudio/GoerzelStream.h

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Member Function Documentation

◆ addNotifyAudioChange()

◆ audioInfo()

◆ audioInfoOut()

◆ available()

◆ availableForWrite()

◆ begin() [1/2]

◆ begin() [2/2]

◆ checkDetection()

◆ clip()

◆ end()

◆ flush()

◆ getConfig()

◆ getCurrentMagnitude()

◆ isFrequencyDetected()

◆ operator bool()

◆ processSamples()

◆ processSamplesOfType()

◆ readBytes()

◆ setAudioInfo()

◆ setChannelDetectionCallback()

◆ setReference()

◆ write() [1/2]

◆ write() [2/2]