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# cocos.audio.pygame.mixer module

Pygame module for loading and playing sounds.

This module contains classes for loading Sound objects and controlling playback. The mixer module is optional and depends on SDL_mixer. Your program should test that pygame.mixer is available and intialized before using it.

The mixer module has a limited number of channels for playback of sounds. Usually programs tell pygame to start playing audio and it selects an available channel automatically. The default is 8 simultaneous channels, but complex programs can get more precise control over the number of channels and their use.

All sound playback is mixed in background threads. When you begin to play a Sound object, it will return immediately while the sound continues to play. A single Sound object can also be actively played back multiple times.

The mixer also has a special streaming channel. This is for music playback and is accessed through the pygame.mixer.music module.

The mixer module must be initialized like other pygame modules, but it has some extra conditions. The pygame.mixer.init() function takes several optional arguments to control the playback rate and sample size. Pygame will default to reasonable values, but pygame cannot perform Sound resampling, so the mixer should be initialized to match the values of your audio resources.

NOTE: there is currently a bug on some windows machines which makes sound play back ‘scratchy’. There is not enough cpu in the sound thread to feed the buffer to the sound api. To get around this you can increase the buffer size. However this means that there is more of a delay between the time you ask to play the sound and when it gets played. Try calling this before the pygame.init or pygame.mixer.init calls. pygame.mixer.pre_init(44100,-16,2, 1024 * 3)

class `Channel`(id)

  Bases: `object`

  The Channel object can be used to get fine control over the playback of Sounds. A channel can only playback a single Sound at time. Using channels is entirely optional since pygame can manage them by default.

  `fadeout`(time)

    Stop playback after fading channel out.

    Stop playback of a channel after fading out the sound over the given time argument in milliseconds.

    Parameters: | time : int Time to fade out, in milliseconds.

  `get_busy`()

    Determine if the channel is active.

    Returns true if the channel is activily mixing sound. If the channel is idle this returns False.

    Return type: | bool

  `get_endevent`()

    Get the event a channel sends when playback stops.

    Returns the event type to be sent every time the Channel finishes playback of a Sound. If there is no endevent the function returns pygame.NOEVENT.

    Return type: | int

  `get_queue`()

    Return any Sound that is queued.

    If a Sound is already queued on this channel it will be returned. Once the queued sound begins playback it will no longer be on the queue.

    Return type: | Sound

  `get_sound`()

    Get the currently playing Sound.

    Return the actual Sound object currently playing on this channel. If the channel is idle None is returned.

    Return type: | Sound

  `get_volume`()

    Get the volume of the playing channel.

    Return the volume of the channel for the current playing sound. This does not take into account stereo separation used by Channel.set_volume. The Sound object also has its own volume which is mixed with the channel.

    Return type: | float

  `pause`()

    Temporarily stop playback of a channel.

    Temporarily stop the playback of sound on a channel. It can be resumed at a later time with Channel.unpause()

  `play`(sound, loops=0, time=-1)

    Play a Sound on a specific Channel.

    This will begin playback of a Sound on a specific Channel. If the Channel is currently playing any other Sound it will be stopped.

    The loops argument has the same meaning as in Sound.play(): it is the number of times to repeat the sound after the first time. If it is 3, the sound will be played 4 times (the first time, then three more). If loops is -1 then the playback will repeat indefinitely.

    As in Sound.play(), the time argument can be used to stop playback of the Sound after a given number of milliseconds.

    Parameters: | sound : Sound Sound data to play. loops : int Number of times to repeat the sound after the first play. time : int Maximum number of milliseconds to play for.

  `queue`(sound)

    Queue a Sound object to follow the current.

    When a Sound is queued on a Channel, it will begin playing immediately after the current Sound is finished. Each channel can only have a single Sound queued at a time. The queued Sound will only play if the current playback finished automatically. It is cleared on any other call to Channel.stop() or Channel.play().

    If there is no sound actively playing on the Channel then the Sound will begin playing immediately.

    Parameters: | sound : Sound Sound data to queue.

  `set_endevent`(id=None)

    Have the channel send an event when playback stops.

    When an endevent is set for a channel, it will send an event to the pygame queue every time a sound finishes playing on that channel (not just the first time). Use pygame.event.get() to retrieve the endevent once it’s sent.

    Note that if you called Sound.play(n) or Channel.play(sound,n), the end event is sent only once: after the sound has been played “n+1” times (see the documentation of Sound.play).

    If Channel.stop() or Channel.play() is called while the sound was still playing, the event will be posted immediately.

    The id argument will be the event id sent to the queue. This can be any valid event type, but a good choice would be a value between pygame.locals.USEREVENT and pygame.locals.NUMEVENTS. If no type argument is given then the Channel will stop sending endevents.

    Parameters: | id : int Event ID to send.

  `set_volume`(left, right=None)

    Set the volume of a playing channel.

    Set the volume (loudness) of a playing sound. When a channel starts to play its volume value is reset. This only affects the current sound. Each argument is between 0.0 and 1.0.

    If one argument is passed, it will be the volume of both speakers. If two arguments are passed and the mixer is in stereo mode, the first argument will be the volume of the left speaker and the second will be the volume of the right speaker. (If the second argument is None, the first argument will be the volume of both speakers.)

    If the channel is playing a Sound on which set_volume() has also been called, both calls are taken into account. For example:

        sound = pygame.mixer.Sound("s.wav")
        channel = s.play()      # Sound plays at full volume by default
        sound.set_volume(0.9)   # Now plays at 90% of full volume.
        sound.set_volume(0.6)   # Now plays at 60% (previous value replaced)
        channel.set_volume(0.5) # Now plays at 30% (0.6 * 0.5).

    Parameters: | left : float Volume of left (or mono) channel, in range [0.0, 1.0] right : float Volume of right channel, in range [0.0, 1.0]

  `stop`()

    Stop playback on a Channel.

    Stop sound playback on a channel. After playback is stopped the channel becomes available for new Sounds to play on it.

  `unpause`()

    Resume pause playback of a channel.

    Resume the playback on a paused channel.

class `Sound`(file, _chunk=None)

  Bases: `object`

  The Sound object represents actual sound sample data.

  Methods that change the state of the Sound object will the all instances of the Sound playback.

  `fadeout`(time)

    Stop sound playback after fading out.

    This will stop playback of the sound after fading it out over the time argument in milliseconds. The Sound will fade and stop on all actively playing channels.

    Parameters: | time : int Time to fade out, in milliseconds.

  `get_length`()

    Get the length of the Sound.

    Return the length of this Sound in seconds.

    Return type: | float

  `get_num_channels`()

    Count how many times this Sound is playing.

    Return the number of active channels this sound is playing on.

    Return type: | int

  `get_volume`()

    Get the playback volume.

    Return a value from 0.0 to 1.0 representing the volume for this Sound.

    Return type: | float

  `play`(loops=0, maxtime=-1)

    Begin sound playback.

    Begin playback of the Sound (i.e., on the computer’s speakers) on an available Channel. This will forcibly select a Channel, so playback may cut off a currently playing sound if necessary.

    The loops argument controls how many times the sample will be repeated after being played the first time. A value of 5 means that the sound will be played once, then repeated five times, and so is played a total of six times. The default value (zero) means the Sound is not repeated, and so is only played once. If loops is set to -1 the Sound will loop indefinitely (though you can still call stop() to stop it).

    The maxtime argument can be used to stop playback after a given number of milliseconds.

    Parameters: | loops : int Number of times to repeat the sound after the first play. maxtime : int Maximum number of milliseconds to play for.
    Return type: | Channel
    Returns: | The Channel object for the channel that was selected.

  `set_volume`(volume)

    Set the playback volume for this Sound.

    This will set the playback volume (loudness) for this Sound. This will immediately affect the Sound if it is playing. It will also affect any future playback of this Sound. The argument is a value from 0.0 to 1.0.

    Parameters: | volume : float Volume of playback, in range [0.0, 1.0]

  `stop`()

    Stop sound playback.

    This will stop the playback of this Sound on any active Channels.

`fadeout`(time)

  Fade out the volume on all sounds before stopping.

  This will fade out the volume on all active channels over the time argument in milliseconds. After the sound is muted the playback will stop.

  Parameters: | time : int Time to fade out, in milliseconds.

`find_channel`(force=False)

  Find an unused channel.

  This will find and return an inactive Channel object. If there are no inactive Channels this function will return None. If there are no inactive channels and the force argument is True, this will find the Channel with the longest running Sound and return it.

  If the mixer has reserved channels from pygame.mixer.set_reserved() then those channels will not be returned here.

  Parameters: | force : bool If True, a playing channel will be returned if no free ones are available.
  Return type: | Channel

`get_busy`()

  Test if any sound is being mixed.

  Returns True if the mixer is busy mixing any channels. If the mixer is idle then this return False.

  Return type: | bool

`get_init`()

  Determine if the mixer is initialized.

  If the mixer is initialized, this returns the playback arguments it is using. If the mixer has not been initialized this returns None

  The value of size follows the same conventions as in init.

  Return type: | (int, int, bool) or None
  Returns: | (frequency, size, stereo)

`get_num_channels`()

  Get the total number of playback channels.

  Returns the number of currently active playback channels.

  Return type: | int

`init`(frequency=None, size=None, stereo=None, buffer=None)

  Initialize the mixer module.

  Initialize the mixer module for Sound loading and playback. The default arguments can be overridden to provide specific audio mixing. The size argument represents how many bits are used for each audio sample. If the value is negative then signed sample values will be used. Positive values mean unsigned audio samples will be used. If the stereo argument is false the mixer will use mono sound.

  The buffer argument controls the number of internal samples used in the sound mixer. The default value should work for most cases. It can be lowered to reduce latency, but sound dropout may occur. It can be raised to larger values to ensure playback never skips, but it will impose latency on sound playback. The buffer size must be a power of two.

  Some platforms require the pygame.mixer module to be initialized after the display modules have initialized. The top level pygame.init() takes care of this automatically, but cannot pass any arguments to the mixer init. To solve this, mixer has a function pygame.mixer.pre_init() to set the proper defaults before the toplevel init is used.

  It is safe to call this more than once, but after the mixer is initialized you cannot change the playback arguments without first calling pygame.mixer.quit().

  Parameters: | frequency : int Sample rate, in Hertz; defaults to 22050 size : int Bits per sample per channel; defaults to -16. Positive values for unsigned values, negative for signed. stereo : int Number of output channels: 1 for mono, 2 for stereo; defaults to 2. buffer : int Byte size of each output channel’s buffer; a power of two; defaults to 1024.

`pause`()

  Temporarily stop playback of all sound channels.

  This will temporarily stop all playback on the active mixer channels. The playback can later be resumed with pygame.mixer.unpause()

`pre_init`(frequency=0, size=0, stereo=0, buffer=0)

  Preset the mixer init arguments.

  Any nonzero arguments change the default values used when the real pygame.mixer.init() is called. The best way to set custom mixer playback values is to call pygame.mixer.pre_init() before calling the top level pygame.init().

  Parameters: | frequency : int Sample rate, in Hertz size : int Bits per sample per channel. Positive values for unsigned values, negative for signed. stereo : bool Number of mixdown channels: False for 1, True for 2. buffer : int Bytes for mixdown buffer size; a power of two.

`quit`()

  Uninitialize the mixer.

  This will uninitialize pygame.mixer. All playback will stop and any loaded Sound objects may not be compatable with the mixer if it is reinitialized later.

`set_num_channels`(channels)

  Set the total number of playback channels.

  Sets the number of available channels for the mixer. The default value is 8. The value can be increased or decreased. If the value is decreased, sounds playing on the truncated channels are stopped.

  Parameters: | channels : int Number of channels

`set_reserved`(channels)

  Reserve channels from being automatically used.

  The mixer can reserve any number of channels that will not be automatically selected for playback by Sounds. If sounds are currently playing on the reserved channels they will not be stopped.

  This allows the application to reserve a specific number of channels for important sounds that must not be dropped or have a guaranteed channel to play on.

  Parameters: | channels : int Number of channels to reserve.

`stop`()

  Stop playback of all sound channels.

  This will stop all playback of all active mixer channels.

`unpause`()

  Resume paused playback of sound channels.

  This will resume all active sound channels after they have been paused.

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