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https://github.com/stetre/moonal

Lua bindings for OpenAL
https://github.com/stetre/moonal

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Lua bindings for OpenAL

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## MoonAL: Lua bindings for OpenAL



MoonAL is a Lua binding library for the [OpenAL 3D Audio Library API](https://openal.org).



It runs on GNU/Linux and on Windows (MSYS2/MinGW) and requires

[Lua](http://www.lua.org/) (>=5.3) and [OpenAL Soft](http://openal-soft.org) (>= 1.18.0).



_Author:_ _[Stefano Trettel](https://www.linkedin.com/in/stetre)_



[![Lua logo](./doc/powered-by-lua.gif)](http://www.lua.org/)



#### License



MIT/X11 license (same as Lua). See [LICENSE](./LICENSE).



#### Documentation



See the [Reference Manual](https://stetre.github.io/moonal/doc/index.html).



#### Getting and installing



Setup the build environment as described [here](https://github.com/stetre/moonlibs), then:



```sh

$ git clone https://github.com/stetre/moonal

$ cd moonal

moonal$ make

moonal$ sudo make install

```



Note: that MoonAL does not link directly to the OpenAL library (`libopenal.so` on Linux), 

but it builds dynamically its own internal dispatch tables instead.

As a consequence, `libopenal.so` is not needed at compile time but it is required 

at runtime, so you have to make sure that it is reachable by the linker. 

You can do this by installing it in the standard search directories (e.g. `/usr/lib/`),

or by properly setting the LD_LIBRARY_PATH environment variable in the shell where you execute

the Lua scripts. 



#### Example



The example below generates and plays a sinusoidal tone on the default output device.



Other examples can be found in the **examples/** directory contained in the release package.



```lua

-- MoonAL example: hello.lua

--

-- Plays a 440hz sinusoidal tone for a few seconds on the default device.

--

-- This example is derived from the altonegen.c example that comes with

-- OpenAL Soft version 1.18.0.

al = require('moonal')



-- Open device and create context:

device = al.open_device()

context = al.create_context(device)



-- Get the device's output frequency:

srate = context:get_attribute('frequency')



-- Generate the sine wave:

data = {}

for i = 1, srate do data[i]=0.0 end

tone_freq = 440

max_loops = 4

smps_per_cycle = srate / tone_freq

for i = 1, srate do

   data[i] = data[i] + math.sin((i-1)/smps_per_cycle*2*math.pi)

end

data = al.pack('float', data)



-- Buffer the audio data into a buffer object:

buffer = al.create_buffer(context)

al.buffer_data(buffer, 'mono float32', data, srate)



-- Create the source to play the sound with, and set its buffer to

-- the buffer containing the sine wave:

source = al.create_source(context)

source:set('buffer', buffer)



-- Play the sound for a while:

num_loops = 0

last_pos = 0

source:set('looping', max_loops > 0)

al.source_play(source)



print("Playing for ".. (max_loops +1) .." seconds ...")

while source:get('state') == 'playing' do

   al.sleep(0.1)

   pos = source:get('sample offset')

   if pos < last_pos then

      num_loops = num_loops + 1

      if num_loops >= max_loops then

         source:set('looping', false)

      end

      print(math.tointeger(max_loops - num_loops + 1) .. " ...")

   end

   last_pos = pos

end



al.close_device(device) -- unneeded, actually (automatically done at exit)

```



The script can be executed at the shell prompt with the standard Lua interpreter:



```shell

$ lua hello.lua

```



#### See also



* [MoonLibs - Graphics and Audio Lua Libraries](https://github.com/stetre/moonlibs).