Sound

Sound API documentation

gain

number sound gain

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

number sound pan

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


speed

number sound speed

The speed on the sound-component where 1.0 is normal speed, 0.5 is half speed and 2.0 is double speed.

EXAMPLES

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


sound

hash sound data

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.is_music_playing()

check if background music is playing

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:

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.

RETURN

playing - true if music is playing, otherwise false.

EXAMPLES

If music is playing, mute "master":

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


sound.get_rms(group, window)

get RMS value from mixer group

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

group - group name

window - window length in seconds

RETURN

rms_l - RMS value for left channel

rms_r - RMS value for right channel

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.get_peak(group, window)

get peak gain value from mixer group

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

group - group name

window - window length in seconds

RETURN

peak_l - peak value for left channel

peak_r - peak value for right channel

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.set_group_gain(group, gain)

set mixer group gain

Set mixer group gain 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

group - group name

gain - gain in linear scale

EXAMPLES

Set mixer group gain on the "soundfx" group to -4 dB:

local gain_db = -4
local gain = 10^gain_db/20 -- 0.63095734448019
sound.set_group_gain("soundfx", gain)


sound.get_group_gain(group)

get mixer group gain

Get mixer group gain 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

group - group name

RETURN

gain - gain in linear scale

EXAMPLES

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

local gain = sound.get_group_gain("soundfx")
local gain_db = 20 * log(gain)


sound.get_groups()

get all mixer group names

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

RETURN

groups - table of mixer group names

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_group_name(group)

get mixer group name string

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

group - group name

RETURN

name - group name

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.is_phone_call_active()

check if a phone call is active

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.

RETURN

call_active - true if there is an active phone call, false otherwise.

EXAMPLES

Test if a phone call is on-going:

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


sound.play(url, [play_properties], [complete_function])

plays a sound

Make the sound component play its sound. Multiple voices are 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 call sound.stop() to stop the sound.

PARAMETERS

url - the sound that should play

[play_properties] -

optional table with properties:
delay
number delay in seconds before the sound starts playing, default is 0.
gain
number sound gain between 0 and 1, default is 1. The final gain of the sound will be a combination of this gain, the group gain and the master gain.
pan
number sound pan between -1 and 1, default is 0. The final pan of the sound will be an addition of this pan and the sound pan.
speed
number sound speed where 1.0 is normal speed, 0.5 is half speed and 2.0 is double speed. The final speed of the sound will be a multiplication of this speed and the sound speed.

[complete_function] - function to call when the sound has finished playing or stopped manually via sound.stop.

self
object The current object.
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.
message
table Information about the completion:
sender
url The invoker of the callback: the sound component.

RETURN

play_id - 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 = 0.5, 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.stop(url, [stop_properties])

stop a playing a sound(s)

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

PARAMETERS

url - the sound component that should stop

[stop_properties] -

optional table with properties:
play_id
number the sequential play identifier that should be stopped (was given by the sound.play() function)

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.pause(url, pause)

pause a playing a sound(s)

Pause all active voices

PARAMETERS

url - the sound that should pause

pause - true if the sound should pause

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.set_gain(url, [gain])

set sound gain

Set gain on all active playing voices of a sound. 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

url - the sound to set the gain of

[gain] - sound gain between 0 and 1. 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 0.5

sound.set_gain("#sound", 0.5)


sound.set_pan(url, [pan])

set sound pan

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.

PARAMETERS

url - the sound to set the panning value to

[pan] - 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


play_sound

plays a sound

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

[delay] - delay in seconds before the sound starts playing, default is 0.

[gain] - sound gain between 0 and 1, default is 1.

[play_id] - the identifier of the sound, can be used to distinguish between consecutive plays from the same component.

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


stop_sound

stop a playing a sound(s)

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")


set_gain

set sound gain

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

[gain] - sound gain between 0 and 1, default is 1.

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_done

reports when a sound has finished playing

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] - id number supplied when the message was posted.


sound_stopped

reports when a sound has been manually stopped

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] - id number supplied when the message was posted.