JUCE  v5.4.1-191-g0ab5e696f
JUCE API
Looking for a senior C++ dev?
I'm looking for work. Hire me!
juce::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 juce::AudioThumbnail:
Collaboration diagram for juce::AudioThumbnail:

Public Member Functions

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

Private Member Functions

void clearChannelData ()
 
void createChannels (int length)
 
bool setDataSource (LevelDataSource *newSource)
 
void setLevels (const MinMaxValue *const *values, int thumbIndex, int numChans, int numValues)
 

Private Attributes

AudioThumbnailCachecache
 
OwnedArray< ThumbData > channels
 
AudioFormatManagerformatManagerToUse
 
CriticalSection lock
 
int32 numChannels = 0
 
int64 numSamplesFinished = 0
 
double sampleRate = 0
 
int32 samplesPerThumbSample = 0
 
std::unique_ptr< LevelDataSource > source
 
int64 totalSamples = 0
 
std::unique_ptr< CachedWindow > window
 

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

{Audio}

Constructor & Destructor Documentation

◆ AudioThumbnail()

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

Creates an audio thumbnail.

Parameters
sourceSamplesPerThumbnailSamplewhen 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)
formatManagerToUsethe audio format manager that is used to open the file
cacheToUsean 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()

juce::AudioThumbnail::~AudioThumbnail ( )
override

Destructor.

Member Function Documentation

◆ addBlock()

void juce::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 juce::AudioFormatWriter::ThreadedWriter::IncomingDataReceiver.

◆ addChangeListener()

void juce::ChangeBroadcaster::addChangeListener ( ChangeListener listener)
inherited

Registers a listener to receive change callbacks from this broadcaster.

Trying to add a listener that's already on the list will have no effect.

◆ clear()

void juce::AudioThumbnail::clear ( )
overridevirtual

Clears and resets the thumbnail.

Implements juce::AudioThumbnailBase.

◆ clearChannelData()

void juce::AudioThumbnail::clearChannelData ( )
private

◆ createChannels()

void juce::AudioThumbnail::createChannels ( int  length)
private

◆ dispatchPendingMessages()

void juce::ChangeBroadcaster::dispatchPendingMessages ( )
inherited

If a change message has been sent but not yet dispatched, this will call sendSynchronousChangeMessage() to make the callback immediately.

For thread-safety reasons, you must only call this method on the main message thread.

◆ drawChannel()

void juce::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 juce::AudioThumbnailBase.

◆ drawChannels()

void juce::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 juce::AudioThumbnailBase.

◆ getApproximateMinMax()

void juce::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 juce::AudioThumbnailBase.

◆ getApproximatePeak()

float juce::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 juce::AudioThumbnailBase.

◆ getHashCode()

int64 juce::AudioThumbnail::getHashCode ( ) const
overridevirtual

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

Implements juce::AudioThumbnailBase.

◆ getNumChannels()

int juce::AudioThumbnail::getNumChannels ( ) const
overridevirtualnoexcept

Returns the number of channels in the file.

Implements juce::AudioThumbnailBase.

◆ getNumSamplesFinished()

int64 juce::AudioThumbnail::getNumSamplesFinished ( ) const
overridevirtualnoexcept

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

Implements juce::AudioThumbnailBase.

◆ getProportionComplete()

double juce::AudioThumbnail::getProportionComplete ( ) const
noexcept

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

◆ getTotalLength()

double juce::AudioThumbnail::getTotalLength ( ) const
overridevirtualnoexcept

Returns the length of the audio file, in seconds.

Implements juce::AudioThumbnailBase.

◆ isFullyLoaded()

bool juce::AudioThumbnail::isFullyLoaded ( ) const
overridevirtualnoexcept

Returns true if the low res preview is fully generated.

Implements juce::AudioThumbnailBase.

◆ loadFrom()

bool juce::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 juce::AudioThumbnailBase.

◆ removeAllChangeListeners()

void juce::ChangeBroadcaster::removeAllChangeListeners ( )
inherited

Removes all listeners from the list.

◆ removeChangeListener()

void juce::ChangeBroadcaster::removeChangeListener ( ChangeListener listener)
inherited

Unregisters a listener from the list.

If the listener isn't on the list, this won't have any effect.

◆ reset()

void juce::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 juce::AudioFormatWriter::ThreadedWriter::IncomingDataReceiver.

◆ saveTo()

void juce::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 juce::AudioThumbnailBase.

◆ sendChangeMessage()

void juce::ChangeBroadcaster::sendChangeMessage ( )
inherited

Causes an asynchronous change message to be sent to all the registered listeners.

The message will be delivered asynchronously by the main message thread, so this method will return immediately. To call the listeners synchronously use sendSynchronousChangeMessage().

Referenced by juce::SelectedItemSet< SelectableItemType >::changed().

◆ sendSynchronousChangeMessage()

void juce::ChangeBroadcaster::sendSynchronousChangeMessage ( )
inherited

Sends a synchronous change message to all the registered listeners.

This will immediately call all the listeners that are registered. For thread-safety reasons, you must only call this method on the main message thread.

See also
dispatchPendingMessages

Referenced by juce::SelectedItemSet< SelectableItemType >::changed().

◆ setDataSource()

bool juce::AudioThumbnail::setDataSource ( LevelDataSource *  newSource)
private

◆ setLevels()

void juce::AudioThumbnail::setLevels ( const MinMaxValue *const *  values,
int  thumbIndex,
int  numChans,
int  numValues 
)
private

◆ setReader()

void juce::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 juce::AudioThumbnailBase.

◆ setSource()

bool juce::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 juce::AudioThumbnailBase.

Member Data Documentation

◆ cache

AudioThumbnailCache& juce::AudioThumbnail::cache
private

◆ channels

OwnedArray<ThumbData> juce::AudioThumbnail::channels
private

◆ formatManagerToUse

AudioFormatManager& juce::AudioThumbnail::formatManagerToUse
private

◆ lock

CriticalSection juce::AudioThumbnail::lock
private

◆ numChannels

int32 juce::AudioThumbnail::numChannels = 0
private

◆ numSamplesFinished

int64 juce::AudioThumbnail::numSamplesFinished = 0
private

◆ sampleRate

double juce::AudioThumbnail::sampleRate = 0
private

◆ samplesPerThumbSample

int32 juce::AudioThumbnail::samplesPerThumbSample = 0
private

◆ source

std::unique_ptr<LevelDataSource> juce::AudioThumbnail::source
private

◆ totalSamples

int64 juce::AudioThumbnail::totalSamples = 0
private

◆ window

std::unique_ptr<CachedWindow> juce::AudioThumbnail::window
private

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