AudioThumbnail Class Reference

Makes it easy to quickly draw scaled views of the waveform shape of an audio file. More...

#include <juce_AudioThumbnail.h>

Inheritance diagram for AudioThumbnail:

Public Member Functions
	AudioThumbnail (int sourceSamplesPerThumbnailSample, AudioFormatManager &formatManagerToUse, AudioThumbnailCache &cacheToUse)
	Creates an audio thumbnail.
	~AudioThumbnail () override
	Destructor.
void	clear () override
	Clears and resets the thumbnail.
bool	setSource (InputSource *newSource) override
	Specifies the file or stream that contains the audio file.
void	setReader (AudioFormatReader *newReader, int64 hashCode) override
	Gives the thumbnail an AudioFormatReader to use directly.
void	setSource (const AudioBuffer< float > *newSource, double sampleRate, int64 hashCode)
	Sets an AudioBuffer as the source for the thumbnail.
void	setSource (const AudioBuffer< int > *newSource, double sampleRate, int64 hashCode)
	Same as the other setSource() overload except for int data.
void	reset (int numChannels, double sampleRate, int64 totalSamplesInSource=0) override
	Resets the thumbnail, ready for adding data with the specified format.
void	addBlock (int64 sampleNumberInSource, const AudioBuffer< float > &newData, int startOffsetInBuffer, int numSamples) override
	Adds a block of level data to the thumbnail.
bool	loadFrom (InputStream &input) override
	Reloads the low res thumbnail data from an input stream.
void	saveTo (OutputStream &output) const override
	Saves the low res thumbnail data to an output stream.
int	getNumChannels () const noexcept override
	Returns the number of channels in the file.
double	getTotalLength () const noexcept override
	Returns the length of the audio file, in seconds.
void	drawChannel (Graphics &g, const Rectangle< int > &area, double startTimeSeconds, double endTimeSeconds, int channelNum, float verticalZoomFactor) override
	Draws the waveform for a channel.
void	drawChannels (Graphics &g, const Rectangle< int > &area, double startTimeSeconds, double endTimeSeconds, float verticalZoomFactor) override
	Draws the waveforms for all channels in the thumbnail.
bool	isFullyLoaded () const noexcept override
	Returns true if the low res preview is fully generated.
double	getProportionComplete () const noexcept
	Returns a value between 0 and 1 to indicate the progress towards loading the entire file.
int64	getNumSamplesFinished () const noexcept override
	Returns the number of samples that have been set in the thumbnail.
float	getApproximatePeak () const override
	Returns the highest level in the thumbnail.
void	getApproximateMinMax (double startTime, double endTime, int channelIndex, float &minValue, float &maxValue) const noexcept override
	Reads the approximate min and max levels from a section of the thumbnail.
int64	getHashCode () const override
	Returns the hash code that was set by setSource() or setReader().
Public Member Functions inherited from AudioThumbnailBase
	AudioThumbnailBase ()=default
	~AudioThumbnailBase () override=default
Public Member Functions inherited from ChangeBroadcaster
	ChangeBroadcaster () noexcept
	Creates an ChangeBroadcaster.
virtual	~ChangeBroadcaster ()
	Destructor.
void	addChangeListener (ChangeListener *listener)
	Registers a listener to receive change callbacks from this broadcaster.
void	removeChangeListener (ChangeListener *listener)
	Unregisters a listener from the list.
void	removeAllChangeListeners ()
	Removes all listeners from the list.
void	sendChangeMessage ()
	Causes an asynchronous change message to be sent to all the registered listeners.
void	sendSynchronousChangeMessage ()
	Sends a synchronous change message to all the registered listeners.
void	dispatchPendingMessages ()
	If a change message has been sent but not yet dispatched, this will call sendSynchronousChangeMessage() to make the callback immediately.
Public Member Functions inherited from AudioFormatWriter::ThreadedWriter::IncomingDataReceiver
	IncomingDataReceiver ()=default
virtual	~IncomingDataReceiver ()=default

Detailed Description

Makes it easy to quickly draw scaled views of the waveform shape of an audio file.

To use this class, just create an AudioThumbnail class for the file you want to draw, call setSource to tell it which file or resource to use, then call drawChannel() to draw it.

The class will asynchronously scan the wavefile to create its scaled-down view, so you should make your UI repaint itself as this data comes in. To do this, the AudioThumbnail is a ChangeBroadcaster, and will broadcast a message when its listeners should repaint themselves.

The thumbnail stores an internal low-res version of the wave data, and this can be loaded and saved to avoid having to scan the file again.

See also

AudioThumbnailCache, AudioThumbnailBase

Constructor & Destructor Documentation

AudioThumbnail()

AudioThumbnail::AudioThumbnail	(	int	sourceSamplesPerThumbnailSample,
		AudioFormatManager &	formatManagerToUse,
		AudioThumbnailCache &	cacheToUse )

Creates an audio thumbnail.

Parameters

sourceSamplesPerThumbnailSample	when creating a stored, low-res version of the audio data, this is the scale at which it should be done. (This number is the number of original samples that will be averaged for each low-res sample)
formatManagerToUse	the audio format manager that is used to open the file
cacheToUse	an instance of an AudioThumbnailCache - this provides a background thread and storage that is used to by the thumbnail, and the cache object can be shared between multiple thumbnails

~AudioThumbnail()

AudioThumbnail::~AudioThumbnail ( )

override

Destructor.

Member Function Documentation

clear()

void AudioThumbnail::clear ( )

overridevirtual

Clears and resets the thumbnail.

Implements AudioThumbnailBase.

setSource() [1/3]

bool AudioThumbnail::setSource ( InputSource * newSource )

overridevirtual

Specifies the file or stream that contains the audio file.

For a file, just call

setSource (new FileInputSource (file))

You can pass a nullptr in here to clear the thumbnail. The source that is passed in will be deleted by this object when it is no longer needed.

Returns

true if the source could be opened as a valid audio file, false if this failed for some reason.

Implements AudioThumbnailBase.

setReader()

void AudioThumbnail::setReader ( AudioFormatReader * newReader, int64 hashCode )

overridevirtual

Gives the thumbnail an AudioFormatReader to use directly.

This will start parsing the audio in a background thread (unless the hash code can be looked-up successfully in the thumbnail cache). Note that the reader object will be held by the thumbnail and deleted later when no longer needed. The thumbnail will actually keep hold of this reader until you clear the thumbnail or change the input source, so the file will be held open for all this time. If you don't want the thumbnail to keep a file handle open continuously, you should use the setSource() method instead, which will only open the file when it needs to.

Implements AudioThumbnailBase.

setSource() [2/3]

void AudioThumbnail::setSource	(	const AudioBuffer< float > *	newSource,
		double	sampleRate,
		int64	hashCode )

Sets an AudioBuffer as the source for the thumbnail.

The buffer contents aren't copied and you must ensure that the lifetime of the buffer is valid for as long as the AudioThumbnail uses it as its source. Calling this function will start reading the audio in a background thread (unless the hash code can be looked-up successfully in the thumbnail cache).

setSource() [3/3]

void AudioThumbnail::setSource	(	const AudioBuffer< int > *	newSource,
		double	sampleRate,
		int64	hashCode )

Same as the other setSource() overload except for int data.

reset()

void AudioThumbnail::reset ( int numChannels, double sampleRate, int64 totalSamplesInSource = 0 )

overridevirtual

Resets the thumbnail, ready for adding data with the specified format.

If you're going to generate a thumbnail yourself, call this before using addBlock() to add the data.

Implements AudioFormatWriter::ThreadedWriter::IncomingDataReceiver.

addBlock()

void AudioThumbnail::addBlock ( int64 sampleNumberInSource, const AudioBuffer< float > & newData, int startOffsetInBuffer, int numSamples )

overridevirtual

Adds a block of level data to the thumbnail.

Call reset() before using this, to tell the thumbnail about the data format.

Implements AudioFormatWriter::ThreadedWriter::IncomingDataReceiver.

loadFrom()

bool AudioThumbnail::loadFrom ( InputStream & input )

overridevirtual

Reloads the low res thumbnail data from an input stream.

This is not an audio file stream! It takes a stream of thumbnail data that would previously have been created by the saveTo() method.

See also

saveTo

Implements AudioThumbnailBase.

saveTo()

void AudioThumbnail::saveTo ( OutputStream & output ) const

overridevirtual

Saves the low res thumbnail data to an output stream.

The data that is written can later be reloaded using loadFrom().

See also

loadFrom

Implements AudioThumbnailBase.

getNumChannels()

int AudioThumbnail::getNumChannels ( ) const

overridevirtualnoexcept

Returns the number of channels in the file.

Implements AudioThumbnailBase.

getTotalLength()

double AudioThumbnail::getTotalLength ( ) const

overridevirtualnoexcept

Returns the length of the audio file, in seconds.

Implements AudioThumbnailBase.

drawChannel()

void AudioThumbnail::drawChannel ( Graphics & g, const Rectangle< int > & area, double startTimeSeconds, double endTimeSeconds, int channelNum, float verticalZoomFactor )

overridevirtual

Draws the waveform for a channel.

The waveform will be drawn within the specified rectangle, where startTime and endTime specify the times within the audio file that should be positioned at the left and right edges of the rectangle.

The waveform will be scaled vertically so that a full-volume sample will fill the rectangle vertically, but you can also specify an extra vertical scale factor with the verticalZoomFactor parameter.

Implements AudioThumbnailBase.

drawChannels()

void AudioThumbnail::drawChannels ( Graphics & g, const Rectangle< int > & area, double startTimeSeconds, double endTimeSeconds, float verticalZoomFactor )

overridevirtual

Draws the waveforms for all channels in the thumbnail.

This will call drawChannel() to render each of the thumbnail's channels, stacked above each other within the specified area.

See also

drawChannel

Implements AudioThumbnailBase.

isFullyLoaded()

bool AudioThumbnail::isFullyLoaded ( ) const

overridevirtualnoexcept

Returns true if the low res preview is fully generated.

Implements AudioThumbnailBase.

getProportionComplete()

double AudioThumbnail::getProportionComplete ( ) const

noexcept

Returns a value between 0 and 1 to indicate the progress towards loading the entire file.

getNumSamplesFinished()

int64 AudioThumbnail::getNumSamplesFinished ( ) const

overridevirtualnoexcept

Returns the number of samples that have been set in the thumbnail.

Implements AudioThumbnailBase.

getApproximatePeak()

float AudioThumbnail::getApproximatePeak ( ) const

overridevirtual

Returns the highest level in the thumbnail.

Note that because the thumb only stores low-resolution data, this isn't an accurate representation of the highest value, it's only a rough approximation.

Implements AudioThumbnailBase.

getApproximateMinMax()

void AudioThumbnail::getApproximateMinMax ( double startTime, double endTime, int channelIndex, float & minValue, float & maxValue ) const

overridevirtualnoexcept

Reads the approximate min and max levels from a section of the thumbnail.

The lowest and highest samples are returned in minValue and maxValue, but obviously because the thumb only stores low-resolution data, these numbers will only be a rough approximation of the true values.

Implements AudioThumbnailBase.

getHashCode()

int64 AudioThumbnail::getHashCode ( ) const

overridevirtual

Returns the hash code that was set by setSource() or setReader().

Implements AudioThumbnailBase.

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

• juce_AudioThumbnail.h