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Sound

Namespace: sound Language: Lua Type: Defold Lua File: script_sound.cpp Source: engine/gamesys/src/gamesys/scripts/script_sound.cpp

Functions and messages for controlling sound components and mixer groups.

API

gain

Type: PROPERTY The gain on the sound-component. Note that gain is in linear scale, between 0 and 1.

Examples

function init(self)
  local gain = go.get("#sound", "gain")
  go.set("#sound", "gain", gain * 1.5)
end

pan

Type: PROPERTY The pan on the sound-component. The valid range is from -1.0 to 1.0, representing -45 degrees left, to +45 degrees right.

Examples

function init(self)
  local pan = go.get("#sound", "pan")
  go.set("#sound", "pan", pan * -1)
end

play_sound

Type: MESSAGE Post this message to a sound-component to make it play its sound. Multiple voices is supported. The limit is set to 32 voices per sound component. Note that gain is in linear scale, between 0 and 1. To get the dB value from the gain, use the formula 20 * log(gain). Inversely, to find the linear value from a dB value, use the formula 10db/20. A sound will continue to play even if the game object the sound component belonged to is deleted. You can send a stop_sound to stop the sound. play_id should be specified in case you want to receive sound_done or sound_stopped in on_message().

Parameters

Examples

Assuming the script belongs to an instance with a sound-component with id “sound”, this will make the component play its sound after 1 second:

msg.post("#sound", "play_sound", {delay = 1, gain = 0.5})


-- use `play_id` and `msg.post()` if you want to recieve `sound_done` or `sound_stopped` in on_message()
function init()
 msg.post("#sound", "play_sound", {play_id = 1, delay = 1, gain = 0.5})
end

function on_message(self, message_id, message)
 if message_id == hash("sound_done") then
     print("Sound play id: "..message.play_id)
 end
end

set_gain

Type: MESSAGE Post this message to a sound-component to set gain on all active playing voices. Note that gain is in linear scale, between 0 and 1. To get the dB value from the gain, use the formula 20 * log(gain). Inversely, to find the linear value from a dB value, use the formula 10db/20.

Parameters

Examples

Assuming the script belongs to an instance with a sound-component with id “sound”, this will set the gain to 0.5

msg.post("#sound", "set_gain", {gain = 0.5})

sound

Type: PROPERTY The sound data used when playing the sound. The type of the property is hash.

Examples

How to change the sound:

function init(self)
  -- load a wav file bundled as a custom resource
  local wav = sys.load_resource("foo.wav")
  -- get resource path to the sound component
  local resource_path = go.get("#sound", "sound")
  -- update the resource with the loaded wav file
  resource.set_sound(resource_path, wav)
  -- play the updated sound
  sound.play("#sound")
end

sound.get_group_gain

Type: FUNCTION Get mixer group gain

Parameters

Returns

Examples

Get the mixer group gain for the “soundfx” and convert to dB:

local gain = sound.get_group_gain("soundfx")
local gain_db = 60 * gain

sound.get_group_name

Type: FUNCTION Get a mixer group name as a string. This function is to be used for debugging and development tooling only. The function does a reverse hash lookup, which does not return a proper string value when the game is built in release mode.

Parameters

Returns

Examples

Get the mixer group string names so we can show them as labels on a dev mixer overlay:

local groups = sound.get_groups()
for _,group in ipairs(groups) do
    local name = sound.get_group_name(group)
    msg.post("/mixer_overlay#gui", "set_mixer_label", { group = group, label = name})
end

sound.get_groups

Type: FUNCTION Get a table of all mixer group names (hashes).

Returns

Examples

Get the mixer groups, set all gains to 0 except for “master” and “soundfx” where gain is set to 1:

local groups = sound.get_groups()
for _,group in ipairs(groups) do
    if group == hash("master") or group == hash("soundfx") then
        sound.set_group_gain(group, 1)
    else
        sound.set_group_gain(group, 0)
    end
end

sound.get_peak

Type: FUNCTION Get peak value from mixer group. Note that gain is in linear scale, between 0 and 1. To get the dB value from the gain, use the formula 20 * log(gain). Inversely, to find the linear value from a dB value, use the formula 10db/20. Also note that the returned value might be an approximation and in particular the effective window might be larger than specified.

Parameters

Returns

Examples

Get the peak gain from the “master” group and convert to dB for displaying:

local left_p, right_p = sound.get_peak("master", 0.1)
left_p_db = 20 * log(left_p)
right_p_db = 20 * log(right_p)

sound.get_rms

Type: FUNCTION Get RMS (Root Mean Square) value from mixer group. This value is the square root of the mean (average) value of the squared function of the instantaneous values. For instance: for a sinewave signal with a peak gain of -1.94 dB (0.8 linear), the RMS is 0.8 × 1/sqrt(2) which is about 0.566. Note the returned value might be an approximation and in particular the effective window might be larger than specified.

Parameters

Returns

Examples

Get the RMS from the “master” group where a mono -1.94 dB sinewave is playing:

local rms = sound.get_rms("master", 0.1) -- throw away right channel.
print(rms) --> 0.56555819511414

sound.is_music_playing

Type: FUNCTION Checks if background music is playing, e.g. from iTunes. On non mobile platforms, this function always return false. On Android you can only get a correct reading of this state if your game is not playing any sounds itself. This is a limitation in the Android SDK. If your game is playing any sounds, even with a gain of zero, this function will return false. The best time to call this function is:

In the init function of your main collection script before any sounds are triggered In a window listener callback when the window.WINDOW_EVENT_FOCUS_GAINED event is received

Both those times will give you a correct reading of the state even when your application is swapped out and in while playing sounds and it works equally well on Android and iOS.

Returns

Examples

If music is playing, mute “master”:

if sound.is_music_playing() then
    -- mute "master"
    sound.set_group_gain("master", 0)
end

sound.is_phone_call_active

Type: FUNCTION Checks if a phone call is active. If there is an active phone call all other sounds will be muted until the phone call is finished. On non mobile platforms, this function always return false.

Returns

Examples

Test if a phone call is on-going:

if sound.is_phone_call_active() then
    -- do something sensible.
end

sound.pause

Type: FUNCTION Pause all active voices

Parameters

Examples

Assuming the script belongs to an instance with a sound-component with id “sound”, this will make the component pause all playing voices:

sound.pause("#sound", true)

sound.play

Type: FUNCTION Make the sound component play its sound. Multiple voices are supported. The limit is set to 32 voices per sound component. A sound will continue to play even if the game object the sound component belonged to is deleted. You can call sound.stop() to stop the sound.

Notes

Parameters

self:script_instance

The current script instance.</dd>

message_id:hash

The name of the completion message, which can be either "sound_done" if the sound has finished playing, or "sound_stopped" if it was stopped manually.</dd>

message:sound.play_completion

Information about the completed or stopped playback.</dd>

sender:url

The invoker of the callback: the sound component.</dd> </dl>

Returns

  • play_id (number) - The identifier for the sound voice

Examples

Assuming the script belongs to an instance with a sound-component with id “sound”, this will make the component play its sound after 1 second:

sound.play("#sound", { delay = 1, gain = 0.9, pan = -1.0 } )

Using the callback argument, you can chain several sounds together:

local function sound_done(self, message_id, message, sender)
  -- play 'boom' sound fx when the countdown has completed
  if message_id == hash("sound_done") and message.play_id == self.countdown_id then
    sound.play("#boom", nil, sound_done)
  end
end

function init(self)
  self.countdown_id = sound.play("#countdown", nil, sound_done)
end

sound.play_completion

Type: STRUCT Data passed to the completion callback of sound.play. The callback’s message_id indicates whether playback finished or was stopped manually.

Members

  • play_id (number) - The sequential play identifier for the playback.

sound.play_properties

Type: STRUCT Sound playback properties

Members

  • delay? (number) - Delay in seconds before playback starts. The default is 0.
  • gain? (number) - Gain from 0 to 1. The default is 1; this combines with the group and master gains.
  • pan? (number) - Pan from -1 to 1. The default is 0; this is added to the component pan.
  • speed? (number) - Playback speed from 0 to 50. The default is 1; this is multiplied by the component speed.
  • start_time? (number) - Playback offset in seconds. Mutually exclusive with start_frame.
  • start_frame? (number) - Playback offset in frames or samples. Takes precedence over start_time.

sound.set_gain

Type: FUNCTION Set gain on all active playing voices of a sound.

Parameters

  • url (string hash url) - the sound to set the gain of
  • gain (number) (optional) - sound gain between 0 and 1 [-60dB .. 0dB]. The final gain of the sound will be a combination of this gain, the group gain and the master gain.

Examples

Assuming the script belongs to an instance with a sound-component with id “sound”, this will set the gain to 0.9

sound.set_gain("#sound", 0.9)

sound.set_group_gain

Type: FUNCTION Set mixer group gain

Parameters

  • group (string hash) - group name
  • gain (number) - gain in range [0..1] mapped to [0 .. -60dB]

Examples

Set mixer group gain on the “soundfx” group to 50% (-30dB):

sound.set_group_gain("soundfx", 0.5)

sound.set_pan

Type: FUNCTION Set panning on all active playing voices of a sound. The valid range is from -1.0 to 1.0, representing -45 degrees left, to +45 degrees right.

Notes

  • Sounds are panned using a constant power panning (non linear fade). 0 means left/right channels are balanced at 71%/71% each. At -1 (full left) the channels are at 100%/0%, and 1 they’re at 0%/100%.

Parameters

  • url (string hash url) - the sound to set the panning value to
  • pan (number) (optional) - sound panning between -1.0 and 1.0

Examples

Assuming the script belongs to an instance with a sound-component with id “sound”, this will set the gain to 0.5

sound.set_pan("#sound", 0.5) -- pan to the right

sound.stop

Type: FUNCTION Stop playing all active voices or just one voice if play_id provided

Parameters

  • url (string hash url) - the sound component that should stop
  • stop_properties (sound.stop_properties) (optional) - optional playback to stop

Examples

Assuming the script belongs to an instance with a sound-component with id “sound”, this will make the component stop all playing voices:

sound.stop("#sound")
local id = sound.play("#sound")
sound.stop("#sound", {play_id = id})

sound.stop_properties

Type: STRUCT Sound stop properties

Members

  • play_id (number) - Sequential playback identifier returned by sound.play.

sound_done

Type: MESSAGE This message is sent back to the sender of a play_sound message if the sound could be played to completion and a play_id was provided with the play_sound message.

Parameters

  • play_id (number) (optional) - id number supplied when the message was posted.

sound_stopped

Type: MESSAGE This message is sent back to the sender of a play_sound message, if the sound has been manually stopped and a play_id was provided with the play_sound message.

Parameters

  • play_id (number) (optional) - id number supplied when the message was posted.

speed

Type: PROPERTY The speed on the sound-component where 1.0 is normal speed, 0.5 is half speed and 2.0 is double speed. Valid range is 0.0 to 50.0.

Examples

function init(self)
  local speed = go.get("#sound", "speed")
  go.set("#sound", "speed", speed * 0.5)
end

stop_sound

Type: MESSAGE Post this message to a sound-component to make it stop playing all active voices

Examples

Assuming the script belongs to an instance with a sound-component with id “sound”, this will make the component stop all playing voices:

msg.post("#sound", "stop_sound")