sf::SoundRecorder Class Reference

Abstract base class for capturing sound data. More...

#include <SFML/Audio/SoundRecorder.hpp>

Inheritance diagram for sf::SoundRecorder:

Public Member Functions
virtual	~SoundRecorder ()
	destructor
bool	start (unsigned int sampleRate=44100)
	Start the capture.
void	stop ()
	Stop the capture.
unsigned int	getSampleRate () const
	Get the sample rate.
bool	setDevice (const std::string &name)
	Set the audio capture device.
const std::string &	getDevice () const
	Get the name of the current audio capture device.
void	setChannelCount (unsigned int channelCount)
	Set the channel count of the audio capture device.
unsigned int	getChannelCount () const
	Get the number of channels used by this recorder.

Static Public Member Functions
static std::vector< std::string >	getAvailableDevices ()
	Get a list of the names of all available audio capture devices.
static std::string	getDefaultDevice ()
	Get the name of the default audio capture device.
static bool	isAvailable ()
	Check if the system supports audio capture.

Protected Member Functions
	SoundRecorder ()
	Default constructor.
void	setProcessingInterval (Time interval)
	Set the processing interval.
virtual bool	onStart ()
	Start capturing audio data.
virtual bool	onProcessSamples (const Int16 *samples, std::size_t sampleCount)=0
	Process a new chunk of recorded samples.
virtual void	onStop ()
	Stop capturing audio data.

Detailed Description

Abstract base class for capturing sound data.

sf::SoundBuffer provides a simple interface to access the audio recording capabilities of the computer (the microphone).

As an abstract base class, it only cares about capturing sound samples, the task of making something useful with them is left to the derived class. Note that SFML provides a built-in specialization for saving the captured data to a sound buffer (see sf::SoundBufferRecorder).

A derived class has only one virtual function to override:

• onProcessSamples provides the new chunks of audio samples while the capture happens

Moreover, two additional virtual functions can be overridden as well if necessary:

• onStart is called before the capture happens, to perform custom initializations
• onStop is called after the capture ends, to perform custom cleanup

A derived class can also control the frequency of the onProcessSamples calls, with the setProcessingInterval protected function. The default interval is chosen so that recording thread doesn't consume too much CPU, but it can be changed to a smaller value if you need to process the recorded data in real time, for example.

The audio capture feature may not be supported or activated on every platform, thus it is recommended to check its availability with the isAvailable() function. If it returns false, then any attempt to use an audio recorder will fail.

If you have multiple sound input devices connected to your computer (for example: microphone, external soundcard, webcam mic, ...) you can get a list of all available devices through the getAvailableDevices() function. You can then select a device by calling setDevice() with the appropriate device. Otherwise the default capturing device will be used.

By default the recording is in 16-bit mono. Using the setChannelCount method you can change the number of channels used by the audio capture device to record. Note that you have to decide whether you want to record in mono or stereo before starting the recording.

It is important to note that the audio capture happens in a separate thread, so that it doesn't block the rest of the program. In particular, the onProcessSamples virtual function (but not onStart and not onStop) will be called from this separate thread. It is important to keep this in mind, because you may have to take care of synchronization issues if you share data between threads. Another thing to bear in mind is that you must call stop() in the destructor of your derived class, so that the recording thread finishes before your object is destroyed.

Usage example:

class CustomRecorder : public sf::SoundRecorder
{
public:
    ~CustomRecorder()
    {
        // Make sure to stop the recording thread
        stop();
    }
 
private:
    virtual bool onStart() // optional
    {
        // Initialize whatever has to be done before the capture starts
        ...
 
        // Return true to start playing
        return true;
    }
 
    virtual bool onProcessSamples(const sf::Int16* samples, std::size_t sampleCount)
    {
        // Do something with the new chunk of samples (store them, send them, ...)
        ...
 
        // Return true to continue playing
        return true;
    }
 
    virtual void onStop() // optional
    {
        // Clean up whatever has to be done after the capture ends
        ...
    }
};
 
// Usage
if (CustomRecorder::isAvailable())
{
    CustomRecorder recorder;
 
    if (!recorder.start())
        return -1;
 
    ...
    recorder.stop();
}

See also

sf::SoundBufferRecorder

Definition at line 45 of file SoundRecorder.hpp.

Constructor & Destructor Documentation

~SoundRecorder()

virtual sf::SoundRecorder::~SoundRecorder ( )

virtual

destructor

SoundRecorder()

sf::SoundRecorder::SoundRecorder ( )

protected

Default constructor.

This constructor is only meant to be called by derived classes.

Member Function Documentation

getAvailableDevices()

static std::vector< std::string > sf::SoundRecorder::getAvailableDevices ( )

static

Get a list of the names of all available audio capture devices.

This function returns a vector of strings, containing the names of all available audio capture devices.

Returns

A vector of strings containing the names

getChannelCount()

unsigned int sf::SoundRecorder::getChannelCount

(

)

const

Get the number of channels used by this recorder.

Currently only mono and stereo are supported, so the value is either 1 (for mono) or 2 (for stereo).

Returns

Number of channels

See also

setChannelCount

getDefaultDevice()

static std::string sf::SoundRecorder::getDefaultDevice ( )

static

Get the name of the default audio capture device.

This function returns the name of the default audio capture device. If none is available, an empty string is returned.

Returns

The name of the default audio capture device

getDevice()

const std::string & sf::SoundRecorder::getDevice

(

)

const

Get the name of the current audio capture device.

Returns

The name of the current audio capture device

getSampleRate()

unsigned int sf::SoundRecorder::getSampleRate

(

)

const

Get the sample rate.

The sample rate defines the number of audio samples captured per second. The higher, the better the quality (for example, 44100 samples/sec is CD quality).

Returns

Sample rate, in samples per second

isAvailable()

static bool sf::SoundRecorder::isAvailable ( )

static

Check if the system supports audio capture.

This function should always be called before using the audio capture features. If it returns false, then any attempt to use sf::SoundRecorder or one of its derived classes will fail.

Returns

True if audio capture is supported, false otherwise

onProcessSamples()

virtual bool sf::SoundRecorder::onProcessSamples ( const Int16 *  samples, std::size_t  sampleCount  )

protectedpure virtual

Process a new chunk of recorded samples.

This virtual function is called every time a new chunk of recorded data is available. The derived class can then do whatever it wants with it (storing it, playing it, sending it over the network, etc.).

Parameters

samples	Pointer to the new chunk of recorded samples
sampleCount	Number of samples pointed by samples

Returns

True to continue the capture, or false to stop it

Implemented in sf::SoundBufferRecorder.

onStart()

virtual bool sf::SoundRecorder::onStart ( )

protectedvirtual

Start capturing audio data.

This virtual function may be overridden by a derived class if something has to be done every time a new capture starts. If not, this function can be ignored; the default implementation does nothing.

Returns

True to start the capture, or false to abort it

Reimplemented in sf::SoundBufferRecorder.

onStop()

virtual void sf::SoundRecorder::onStop ( )

protectedvirtual

Stop capturing audio data.

This virtual function may be overridden by a derived class if something has to be done every time the capture ends. If not, this function can be ignored; the default implementation does nothing.

Reimplemented in sf::SoundBufferRecorder.

setChannelCount()

void sf::SoundRecorder::setChannelCount

(

unsigned int

channelCount

)

Set the channel count of the audio capture device.

This method allows you to specify the number of channels used for recording. Currently only 16-bit mono and 16-bit stereo are supported.

Parameters

channelCount

Number of channels. Currently only mono (1) and stereo (2) are supported.

See also

getChannelCount

setDevice()

bool sf::SoundRecorder::setDevice

(

const std::string &

name

)

Set the audio capture device.

This function sets the audio capture device to the device with the given name. It can be called on the fly (i.e: while recording). If you do so while recording and opening the device fails, it stops the recording.

Parameters

name	The name of the audio capture device

Returns

True, if it was able to set the requested device

See also

getAvailableDevices, getDefaultDevice

setProcessingInterval()

void sf::SoundRecorder::setProcessingInterval ( Time  interval )

protected

Set the processing interval.

The processing interval controls the period between calls to the onProcessSamples function. You may want to use a small interval if you want to process the recorded data in real time, for example.

Note: this is only a hint, the actual period may vary. So don't rely on this parameter to implement precise timing.

The default processing interval is 100 ms.

Parameters

interval

Processing interval

start()

bool sf::SoundRecorder::start

(

unsigned int

sampleRate = 44100

)

Start the capture.

The sampleRate parameter defines the number of audio samples captured per second. The higher, the better the quality (for example, 44100 samples/sec is CD quality). This function uses its own thread so that it doesn't block the rest of the program while the capture runs. Please note that only one capture can happen at the same time. You can select which capture device will be used, by passing the name to the setDevice() method. If none was selected before, the default capture device will be used. You can get a list of the names of all available capture devices by calling getAvailableDevices().

Parameters

sampleRate

Desired capture rate, in number of samples per second

Returns

True, if start of capture was successful

See also

stop, getAvailableDevices

stop()

void sf::SoundRecorder::stop

(

)

Stop the capture.

See also

start

---

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

• SoundRecorder.hpp