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)
bool	isReady () const override
Common::Mutex &	mutex () override
void	playStream (SoundType type, SoundHandle *handle, AudioStream *input, int id, byte volume, int8 balance, DisposeAfterUse::Flag autofreeStream, bool permanent, bool reverseStereo) override
void	stopAll () override
void	stopID (int id) override
void	stopHandle (SoundHandle handle) override
void	pauseAll (bool paused) override
void	pauseID (int id, bool paused) override
void	pauseHandle (SoundHandle handle, bool paused) override
bool	isSoundIDActive (int id) override
int	getSoundID (SoundHandle handle) override
bool	isSoundHandleActive (SoundHandle handle) override
void	muteSoundType (SoundType type, bool mute) override
bool	isSoundTypeMuted (SoundType type) const override
void	setChannelVolume (SoundHandle handle, byte volume) override
byte	getChannelVolume (SoundHandle handle) override
void	setChannelBalance (SoundHandle handle, int8 balance) override
int8	getChannelBalance (SoundHandle handle) override
void	setChannelFaderL (SoundHandle handle, uint8 scaleL) override
uint8	getChannelFaderL (SoundHandle handle) override
void	setChannelFaderR (SoundHandle handle, uint8 scaleR) override
uint8	getChannelFaderR (SoundHandle handle) override
void	setChannelRate (SoundHandle handle, uint32 rate) override
uint32	getChannelRate (SoundHandle handle) override
void	resetChannelRate (SoundHandle handle) override
uint32	getSoundElapsedTime (SoundHandle handle) override
Timestamp	getElapsedTime (SoundHandle handle) override
void	loopChannel (SoundHandle handle) override
bool	hasActiveChannelOfType (SoundType type) override
void	setVolumeForSoundType (SoundType type, int volume) override
int	getVolumeForSoundType (SoundType type) const override
uint	getOutputRate () const override
bool	getOutputStereo () const override
uint	getOutputBufSize () const override
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()

bool Audio::MixerImpl::isReady ( ) const

inlineoverridevirtual

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()

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

inlineoverridevirtual

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

Implements Audio::Mixer.

playStream()

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

overridevirtual

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()

void Audio::MixerImpl::stopAll ( )

overridevirtual

Stop all currently playing sounds.

Implements Audio::Mixer.

stopID()

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

overridevirtual

Stop playing the sound with the given ID.

Parameters

id	ID of the sound.

Implements Audio::Mixer.

stopHandle()

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

overridevirtual

Stop playing the sound corresponding to the given handle.

Parameters

handle

The sound to stop playing.

Implements Audio::Mixer.

pauseAll()

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

overridevirtual

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

Parameters

paused

True to pause everything, false to unpause.

Implements Audio::Mixer.

pauseID()

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

overridevirtual

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()

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

overridevirtual

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()

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

overridevirtual

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()

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

overridevirtual

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()

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

overridevirtual

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()

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

overridevirtual

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()

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

overridevirtual

Query the mute state for a given sound type.

Parameters

type	Sound type. See SoundType.

Implements Audio::Mixer.

setChannelVolume()

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

overridevirtual

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()

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

overridevirtual

Get the channel volume for the given handle.

Parameters

handle

The sound to affect.

Returns

The channel volume.

Implements Audio::Mixer.

setChannelBalance()

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

overridevirtual

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()

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

overridevirtual

Get the channel balance for the given handle.

Parameters

handle

The sound to affect.

Returns

The channel balance.

Implements Audio::Mixer.

setChannelFaderL()

void Audio::MixerImpl::setChannelFaderL ( SoundHandle  handle, uint8  faderL  )

overridevirtual

Set the channel's left fader level for the given handle.

Parameters

handle	The sound to affect.
faderL	The channel's new left fader level, in the range of 0-255.

Implements Audio::Mixer.

getChannelFaderL()

uint8 Audio::MixerImpl::getChannelFaderL ( SoundHandle  handle )

overridevirtual

Get the channel's left fader level for the given handle.

Parameters

handle

The sound to affect.

Returns

The channel's left fader level.

Implements Audio::Mixer.

setChannelFaderR()

void Audio::MixerImpl::setChannelFaderR ( SoundHandle  handle, uint8  faderR  )

overridevirtual

Set the channel's right fader level for the given handle.

Parameters

handle	The sound to affect.
faderR	The channel's new right fader level, in the range of 0-255.

Implements Audio::Mixer.

getChannelFaderR()

uint8 Audio::MixerImpl::getChannelFaderR ( SoundHandle  handle )

overridevirtual

Get the channel's right fader level for the given handle.

Parameters

handle

The sound to affect.

Returns

The channel's right fader level.

Implements Audio::Mixer.

setChannelRate()

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

overridevirtual

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()

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

overridevirtual

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()

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

overridevirtual

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

Parameters

handle

The sound to affect.

Implements Audio::Mixer.

getSoundElapsedTime()

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

overridevirtual

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

Implements Audio::Mixer.

getElapsedTime()

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

overridevirtual

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

Implements Audio::Mixer.

loopChannel()

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

overridevirtual

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

Implements Audio::Mixer.

hasActiveChannelOfType()

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

overridevirtual

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()

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

overridevirtual

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()

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

overridevirtual

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()

uint Audio::MixerImpl::getOutputRate ( ) const

overridevirtual

Return the output sample rate of the system.

Returns

The output sample rate in Hz.

Implements Audio::Mixer.

getOutputStereo()

bool Audio::MixerImpl::getOutputStereo ( ) const

overridevirtual

Check whether the output is stereo.

Returns

true if output is stereo, false if not.

Implements Audio::Mixer.

getOutputBufSize()

uint Audio::MixerImpl::getOutputBufSize ( ) const

overridevirtual

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.

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

• audio/mixer_intern.h