juce::MidiMessageCollector Class Reference

Detailed Description

Collects incoming realtime MIDI messages and turns them into blocks suitable for processing by a block-based audio callback.

The class can also be used as either a MidiKeyboardState::Listener or a MidiInputCallback so it can easily use a midi input or keyboard component as its source.

See also

MidiMessage, MidiInput

Inheritance diagram for juce::MidiMessageCollector:

Public Member Functions
	MidiMessageCollector ()
	Creates a MidiMessageCollector.
	~MidiMessageCollector () override
	Destructor.
void	reset (double sampleRate)
	Clears any messages from the queue.
void	addMessageToQueue (const MidiMessage &message)
	Takes an incoming real-time message and adds it to the queue.
void	removeNextBlockOfMessages (MidiBuffer &destBuffer, int numSamples)
	Removes all the pending messages from the queue as a buffer.
void	ensureStorageAllocated (size_t bytes)
	Preallocates storage for collected messages.
void	handleNoteOn (MidiKeyboardState *, int midiChannel, int midiNoteNumber, float velocity) override
	Called when one of the MidiKeyboardState's keys is pressed.
void	handleNoteOff (MidiKeyboardState *, int midiChannel, int midiNoteNumber, float velocity) override
	Called when one of the MidiKeyboardState's keys is released.
void	handleIncomingMidiMessage (MidiInput *, const MidiMessage &) override
	Receives an incoming message.
Public Member Functions inherited from juce::MidiKeyboardState::Listener
virtual	~Listener ()=default
Public Member Functions inherited from juce::MidiInputCallback
virtual	~MidiInputCallback ()=default
	Destructor.
virtual void	handlePartialSysexMessage (MidiInput *source, const uint8 *messageData, int numBytesSoFar, double timestamp)
	Notification sent each time a packet of a multi-packet sysex message arrives.

Constructors and Destructors

MidiMessageCollector()

juce::MidiMessageCollector::MidiMessageCollector

(

)

Creates a MidiMessageCollector.

Referenced by handleIncomingMidiMessage().

~MidiMessageCollector()

juce::MidiMessageCollector::~MidiMessageCollector ( )

override

Destructor.

Member Functions

reset()

void juce::MidiMessageCollector::reset

(

double

sampleRate

)

Clears any messages from the queue.

You need to call this method before starting to use the collector, so that it knows the correct sample rate to use.

addMessageToQueue()

void juce::MidiMessageCollector::addMessageToQueue

(

const MidiMessage &

message

)

Takes an incoming real-time message and adds it to the queue.

The message's timestamp is taken, and it will be ready for retrieval as part of the block returned by the next call to removeNextBlockOfMessages().

This method is fully thread-safe when overlapping calls are made with removeNextBlockOfMessages().

removeNextBlockOfMessages()

void juce::MidiMessageCollector::removeNextBlockOfMessages	(	MidiBuffer &	destBuffer,
		int	numSamples )

Removes all the pending messages from the queue as a buffer.

This will also correct the messages' timestamps to make sure they're in the range 0 to numSamples - 1.

This call should be made regularly by something like an audio processing callback, because the time that it happens is used in calculating the midi event positions.

This method is fully thread-safe when overlapping calls are made with addMessageToQueue().

Precondition: numSamples must be greater than 0.

ensureStorageAllocated()

void juce::MidiMessageCollector::ensureStorageAllocated

(

size_t

bytes

)

Preallocates storage for collected messages.

This can be called before audio processing begins to ensure that there is sufficient space for the expected MIDI messages, in order to avoid allocations within the audio callback.

handleNoteOn()

void juce::MidiMessageCollector::handleNoteOn ( MidiKeyboardState * source, int midiChannel, int midiNoteNumber, float velocity )

overridevirtual

Called when one of the MidiKeyboardState's keys is pressed.

This will be called synchronously when the state is either processing a buffer in its MidiKeyboardState::processNextMidiBuffer() method, or when a note is being played with its MidiKeyboardState::noteOn() method.

Note that this callback could happen from an audio callback thread, so be careful not to block, and avoid any UI activity in the callback.

Implements juce::MidiKeyboardState::Listener.

handleNoteOff()

void juce::MidiMessageCollector::handleNoteOff ( MidiKeyboardState * source, int midiChannel, int midiNoteNumber, float velocity )

overridevirtual

Called when one of the MidiKeyboardState's keys is released.

This will be called synchronously when the state is either processing a buffer in its MidiKeyboardState::processNextMidiBuffer() method, or when a note is being played with its MidiKeyboardState::noteOff() method.

Note that this callback could happen from an audio callback thread, so be careful not to block, and avoid any UI activity in the callback.

Implements juce::MidiKeyboardState::Listener.

handleIncomingMidiMessage()

void juce::MidiMessageCollector::handleIncomingMidiMessage ( MidiInput * source, const MidiMessage & message )

overridevirtual

Receives an incoming message.

A MidiInput object will call this method when a midi event arrives. It'll be called on a high-priority system thread, so avoid doing anything time-consuming in here, and avoid making any UI calls. You might find the MidiBuffer class helpful for queueing incoming messages for use later.

Parameters

source	the MidiInput object that generated the message
message	the incoming message. The message's timestamp is set to a value equivalent to (Time::getMillisecondCounter() / 1000.0) to specify the time when the message arrived

Implements juce::MidiInputCallback.

References MidiMessageCollector().