Audio::MixerImpl Class Reference

#include <mixer_intern.h>

Inheritance diagram for Audio::MixerImpl:

Public Member Functions
	MixerImpl (uint sampleRate, bool stereo=true, uint outBufSize=0)
virtual bool	isReady () const
virtual Common::Mutex &	mutex ()
virtual void	playStream (SoundType type, SoundHandle *handle, AudioStream *input, int id, byte volume, int8 balance, DisposeAfterUse::Flag autofreeStream, bool permanent, bool reverseStereo)
virtual void	stopAll ()
virtual void	stopID (int id)
virtual void	stopHandle (SoundHandle handle)
virtual void	pauseAll (bool paused)
virtual void	pauseID (int id, bool paused)
virtual void	pauseHandle (SoundHandle handle, bool paused)
virtual bool	isSoundIDActive (int id)
virtual int	getSoundID (SoundHandle handle)
virtual bool	isSoundHandleActive (SoundHandle handle)
virtual void	muteSoundType (SoundType type, bool mute)
virtual bool	isSoundTypeMuted (SoundType type) const
virtual void	setChannelVolume (SoundHandle handle, byte volume)
virtual byte	getChannelVolume (SoundHandle handle)
virtual void	setChannelBalance (SoundHandle handle, int8 balance)
virtual int8	getChannelBalance (SoundHandle handle)
virtual void	setChannelRate (SoundHandle handle, uint32 rate)
virtual uint32	getChannelRate (SoundHandle handle)
virtual void	resetChannelRate (SoundHandle handle)
virtual uint32	getSoundElapsedTime (SoundHandle handle)
virtual Timestamp	getElapsedTime (SoundHandle handle)
virtual void	loopChannel (SoundHandle handle)
virtual bool	hasActiveChannelOfType (SoundType type)
virtual void	setVolumeForSoundType (SoundType type, int volume)
virtual int	getVolumeForSoundType (SoundType type) const
virtual uint	getOutputRate () const
virtual bool	getOutputStereo () const
virtual uint	getOutputBufSize () const
int	mixCallback (byte *samples, uint len)
void	setReady (bool ready)

Protected Member Functions
void	insertChannel (SoundHandle *handle, Channel *chan)

Additional Inherited Members
Public Types inherited from Audio::Mixer
enum	SoundType { kPlainSoundType = 0, kMusicSoundType = 1, kSFXSoundType = 2, kSpeechSoundType = 3 }
enum	{ kMaxChannelVolume = 255, kMaxMixerVolume = 256 }

Detailed Description

The (default) implementation of the ScummVM audio mixing subsystem.

Backends are responsible for allocating (and later releasing) an instance of this class, which engines can access via OSystem::getMixer().

Initialisation of instances of this class usually happens as follows: 1) Creat a new Audio::MixerImpl instance. 2) Set the hardware output sample rate via the setSampleRate() method. 3) Hook up the mixCallback() in a suitable audio processing thread/callback. 4) Change the mixer into ready mode via setReady(true). 5) Start audio processing (e.g. by resuming the audio thread, if applicable).

In the future, we might make it possible for backends to provide (partial) alternative implementations of the mixer, e.g. to make better use of native sound mixing support on low-end devices.

See also

OSystem::getMixer()

Member Function Documentation

isReady()

virtual bool Audio::MixerImpl::isReady ( ) const

inlinevirtual

Check whether the mixer is ready and set up.

The mixer might not be set up on systems that do not support digital sound output. In such case, the mixer processing might never be called. That, in turn, can cause breakage in games that try to sync with an audio stream. In particular, the AdLib MIDI emulation.

Returns

Whether the mixer is ready and set up.

Implements Audio::Mixer.

mutex()

virtual Common::Mutex& Audio::MixerImpl::mutex ( )

inlinevirtual

Return the mixer's internal mutex so that audio players can use it.

Implements Audio::Mixer.

playStream()

virtual void Audio::MixerImpl::playStream ( SoundType  type, SoundHandle *  handle, AudioStream *  stream, int  id, byte  volume, int8  balance, DisposeAfterUse::Flag  autofreeStream, bool  permanent, bool  reverseStereo  )

virtual

Start playing the given audio stream.

Note that the sound ID assigned here is unique. At most, one stream with the given ID can play at any given time. Trying to play a sound with an ID that is already in use causes the new sound to not be played.

Parameters

type	Type of the stream - voice/SFX/music.
handle	A SoundHandle instance that can be used to reference and control the stream using suitable mixer methods.
stream	The actual AudioStream to be played.
id	Unique ID assigned to this stream.
volume	Volume with which to play the sound, ranging from 0 to 255.
balance	Balance with which to play the sound, ranging from -127 to 127 (full left to full right). 0 is balanced, -128 is invalid.
autofreeStream	If set, the stream will be freed after the playback is finished.
permanent	If set, a plain stopAll call will not stop this particular stream.
reverseStereo	If set, left and right channels will be swapped.

Implements Audio::Mixer.

stopAll()

virtual void Audio::MixerImpl::stopAll ( )

virtual

Stop all currently playing sounds.

Implements Audio::Mixer.

stopID()

virtual void Audio::MixerImpl::stopID ( int  id )

virtual

Stop playing the sound with the given ID.

Parameters

id	ID of the sound.

Implements Audio::Mixer.

stopHandle()

virtual void Audio::MixerImpl::stopHandle ( SoundHandle  handle )

virtual

Stop playing the sound corresponding to the given handle.

Parameters

handle

The sound to stop playing.

Implements Audio::Mixer.

pauseAll()

virtual void Audio::MixerImpl::pauseAll ( bool  paused )

virtual

Pause or unpause all sounds, including all regular and permanent channels.

Parameters

paused

True to pause everything, false to unpause.

Implements Audio::Mixer.

pauseID()

virtual void Audio::MixerImpl::pauseID ( int  id, bool  paused  )

virtual

Pause or unpause the sound with the given ID.

Parameters

id	ID of the sound.
paused	True to pause the sound, false to unpause it.

Implements Audio::Mixer.

pauseHandle()

virtual void Audio::MixerImpl::pauseHandle ( SoundHandle  handle, bool  paused  )

virtual

Pause or unpause the sound corresponding to the given handle.

Parameters

handle	The sound to pause or unpause.
paused	True to pause the sound, false to unpause it.

Implements Audio::Mixer.

isSoundIDActive()

virtual bool Audio::MixerImpl::isSoundIDActive ( int  id )

virtual

Check whether a sound with the given ID is active.

Parameters

id	ID of the sound to query.

Returns

True if the sound is active.

Implements Audio::Mixer.

getSoundID()

virtual int Audio::MixerImpl::getSoundID ( SoundHandle  handle )

virtual

Get the sound ID for the given handle.

Parameters

handle

The sound to query.

Returns

Sound ID if the sound is active.

Implements Audio::Mixer.

isSoundHandleActive()

virtual bool Audio::MixerImpl::isSoundHandleActive ( SoundHandle  handle )

virtual

Check whether a sound with the given handle is active.

Parameters

handle

The sound to query.

Returns

True if the sound is active.

Implements Audio::Mixer.

muteSoundType()

virtual void Audio::MixerImpl::muteSoundType ( SoundType  type, bool  mute  )

virtual

Set the mute state for a given sound type.

Parameters

type	Sound type. See SoundType.
mute	Whether to mute (= true) or not (= false).

Implements Audio::Mixer.

isSoundTypeMuted()

virtual bool Audio::MixerImpl::isSoundTypeMuted ( SoundType  type ) const

virtual

Query the mute state for a given sound type.

Parameters

type	Sound type. See SoundType.

Implements Audio::Mixer.

setChannelVolume()

virtual void Audio::MixerImpl::setChannelVolume ( SoundHandle  handle, byte  volume  )

virtual

Set the channel volume for the given handle.

Parameters

handle	The sound to affect.
volume	The new channel volume, in the range 0 - kMaxChannelVolume.

Implements Audio::Mixer.

getChannelVolume()

virtual byte Audio::MixerImpl::getChannelVolume ( SoundHandle  handle )

virtual

Get the channel volume for the given handle.

Parameters

handle

The sound to affect.

Returns

The channel volume.

Implements Audio::Mixer.

setChannelBalance()

virtual void Audio::MixerImpl::setChannelBalance ( SoundHandle  handle, int8  balance  )

virtual

Set the channel balance for the given handle.

Parameters

handle	The sound to affect.
balance	The new channel balance: (-127 ... 0 ... 127) corresponds to (left ... center ... right)

Implements Audio::Mixer.

getChannelBalance()

virtual int8 Audio::MixerImpl::getChannelBalance ( SoundHandle  handle )

virtual

Get the channel balance for the given handle.

Parameters

handle

The sound to affect.

Returns

The channel balance.

Implements Audio::Mixer.

setChannelRate()

virtual void Audio::MixerImpl::setChannelRate ( SoundHandle  handle, uint32  rate  )

virtual

Set the sample rate for the given handle.

Parameters

handle	The sound to affect.
rate	The new sample rate. Must be less than 131072

Implements Audio::Mixer.

getChannelRate()

virtual uint32 Audio::MixerImpl::getChannelRate ( SoundHandle  handle )

virtual

Get the sample rate for the given handle.

Parameters

handle

The sound to affect.

Returns

The current sample rate of the channel.

Implements Audio::Mixer.

resetChannelRate()

virtual void Audio::MixerImpl::resetChannelRate ( SoundHandle  handle )

virtual

Reset the sample rate of the channel back to its AudioStream's native rate.

Parameters

handle

The sound to affect.

Implements Audio::Mixer.

getSoundElapsedTime()

virtual uint32 Audio::MixerImpl::getSoundElapsedTime ( SoundHandle  handle )

virtual

Get an approximation of for how long the channel has been playing.

Implements Audio::Mixer.

getElapsedTime()

virtual Timestamp Audio::MixerImpl::getElapsedTime ( SoundHandle  handle )

virtual

Get an approximation of for how long the channel has been playing.

Implements Audio::Mixer.

loopChannel()

virtual void Audio::MixerImpl::loopChannel ( SoundHandle  handle )

virtual

Replace the channel's stream with a version that loops indefinitely.

Implements Audio::Mixer.

hasActiveChannelOfType()

virtual bool Audio::MixerImpl::hasActiveChannelOfType ( SoundType  type )

virtual

Check whether any channel of the given sound type is active.

For example, this can be used to check whether any SFX sound is currently playing by checking for type kSFXSoundType.

Parameters

type	The sound type to query.

Returns

True if any channels of the specified type are active.

Implements Audio::Mixer.

setVolumeForSoundType()

virtual void Audio::MixerImpl::setVolumeForSoundType ( SoundType  type, int  volume  )

virtual

Set the volume for the given sound type.

Parameters

type	Sound type.
volume	The new global volume, in the range 0 - kMaxMixerVolume.

Implements Audio::Mixer.

getVolumeForSoundType()

virtual int Audio::MixerImpl::getVolumeForSoundType ( SoundType  type ) const

virtual

Check what the global volume is for a sound type.

Parameters

type	Sound type.

Returns

The global volume, in the range 0 - kMaxMixerVolume.

Implements Audio::Mixer.

getOutputRate()

virtual uint Audio::MixerImpl::getOutputRate ( ) const

virtual

Return the output sample rate of the system.

Returns

The output sample rate in Hz.

Implements Audio::Mixer.

getOutputStereo()

virtual bool Audio::MixerImpl::getOutputStereo ( ) const

virtual

Check whether the output is stereo.

Returns

true if output is stereo, false if not.

Implements Audio::Mixer.

getOutputBufSize()

virtual uint Audio::MixerImpl::getOutputBufSize ( ) const

virtual

Return the output sample buffer size of the system.

The return value is measured in frame units instead of bytes. It can be converted to bytes by multiplying it with the sample size and the number of channels. For example, for 16-bit stereo output it should be multiplied by 4.

Returns

The number of samples processed at each audio callback.

Implements Audio::Mixer.

mixCallback()

int Audio::MixerImpl::mixCallback	(	byte *	samples,
		uint	len
	)

The mixer callback function, to be called at regular intervals by the backend (e.g. from an audio mixing thread). All the actual mixing work is done from here.

Parameters

samples	Sample buffer, in which stereo 16-bit samples will be stored.
len	Length of the provided buffer to fill (in bytes, should be divisible by 4).

Returns

number of sample pairs processed (which can still be silence!)

setReady()

void Audio::MixerImpl::setReady

(

bool

ready

)

Set the internal 'is ready' flag of the mixer. Backends should invoke Mixer::setReady(true) once initialisation of their audio system has been completed.

---

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

• audio/mixer_intern.h