AudioThumbnailBase Class Reference

Provides a base for classes that can store and draw scaled views of an audio waveform. More...

#include <juce_AudioThumbnailBase.h>

Inheritance diagram for AudioThumbnailBase:

Public Member Functions
	AudioThumbnailBase ()=default
	~AudioThumbnailBase () override=default
virtual void	clear ()=0
	Clears and resets the thumbnail.
virtual bool	setSource (InputSource *newSource)=0
	Specifies the file or stream that contains the audio file.
virtual void	setReader (AudioFormatReader *newReader, int64 hashCode)=0
	Gives the thumbnail an AudioFormatReader to use directly.
virtual bool	loadFrom (InputStream &input)=0
	Reloads the low res thumbnail data from an input stream.
virtual void	saveTo (OutputStream &output) const =0
	Saves the low res thumbnail data to an output stream.
virtual int	getNumChannels () const noexcept=0
	Returns the number of channels in the file.
virtual double	getTotalLength () const noexcept=0
	Returns the length of the audio file, in seconds.
virtual void	drawChannel (Graphics &g, const Rectangle< int > &area, double startTimeSeconds, double endTimeSeconds, int channelNum, float verticalZoomFactor)=0
	Draws the waveform for a channel.
virtual void	drawChannels (Graphics &g, const Rectangle< int > &area, double startTimeSeconds, double endTimeSeconds, float verticalZoomFactor)=0
	Draws the waveforms for all channels in the thumbnail.
virtual bool	isFullyLoaded () const noexcept=0
	Returns true if the low res preview is fully generated.
virtual int64	getNumSamplesFinished () const noexcept=0
	Returns the number of samples that have been set in the thumbnail.
virtual float	getApproximatePeak () const =0
	Returns the highest level in the thumbnail.
virtual void	getApproximateMinMax (double startTime, double endTime, int channelIndex, float &minValue, float &maxValue) const noexcept=0
	Reads the approximate min and max levels from a section of the thumbnail.
virtual int64	getHashCode () const =0
	Returns the hash code that was set by setSource() or setReader().
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
virtual void	reset (int numChannels, double sampleRate, int64 totalSamplesInSource)=0
virtual void	addBlock (int64 sampleNumberInSource, const AudioBuffer< float > &newData, int startOffsetInBuffer, int numSamples)=0

Detailed Description

Provides a base for classes that can store and draw scaled views of an audio waveform.

Typically, you'll want to use the derived class AudioThumbnail, which provides a concrete implementation.

See also

AudioThumbnail, AudioThumbnailCache

Constructor & Destructor Documentation

AudioThumbnailBase()

AudioThumbnailBase::AudioThumbnailBase ( )

default

~AudioThumbnailBase()

AudioThumbnailBase::~AudioThumbnailBase ( )

overridedefault

Member Function Documentation

clear()

virtual void AudioThumbnailBase::clear ( )

pure virtual

Clears and resets the thumbnail.

Implemented in AudioThumbnail.

setSource()

virtual bool AudioThumbnailBase::setSource ( InputSource * newSource )

pure virtual

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.

Implemented in AudioThumbnail.

setReader()

virtual void AudioThumbnailBase::setReader ( AudioFormatReader * newReader, int64 hashCode )

pure virtual

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.

Implemented in AudioThumbnail.

loadFrom()

virtual bool AudioThumbnailBase::loadFrom ( InputStream & input )

pure virtual

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

Implemented in AudioThumbnail.

saveTo()

virtual void AudioThumbnailBase::saveTo ( OutputStream & output ) const

pure virtual

Saves the low res thumbnail data to an output stream.

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

See also

loadFrom

Implemented in AudioThumbnail.

getNumChannels()

virtual int AudioThumbnailBase::getNumChannels ( ) const

pure virtualnoexcept

Returns the number of channels in the file.

Implemented in AudioThumbnail.

getTotalLength()

virtual double AudioThumbnailBase::getTotalLength ( ) const

pure virtualnoexcept

Returns the length of the audio file, in seconds.

Implemented in AudioThumbnail.

drawChannel()

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

pure virtual

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.

Implemented in AudioThumbnail.

drawChannels()

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

pure virtual

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

Implemented in AudioThumbnail.

isFullyLoaded()

virtual bool AudioThumbnailBase::isFullyLoaded ( ) const

pure virtualnoexcept

Returns true if the low res preview is fully generated.

Implemented in AudioThumbnail.

getNumSamplesFinished()

virtual int64 AudioThumbnailBase::getNumSamplesFinished ( ) const

pure virtualnoexcept

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

Implemented in AudioThumbnail.

getApproximatePeak()

virtual float AudioThumbnailBase::getApproximatePeak ( ) const

pure virtual

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.

Implemented in AudioThumbnail.

getApproximateMinMax()

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

pure virtualnoexcept

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.

Implemented in AudioThumbnail.

getHashCode()

virtual int64 AudioThumbnailBase::getHashCode ( ) const

pure virtual

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

Implemented in AudioThumbnail.

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

• juce_AudioThumbnailBase.h