Use OpenAL for all platforms

[minggo]

There is a topic in forum: https://discuss.cocos2d-x.org/t/about-audio-engine-of-cocos-v4/47747.

[halx99]

Great

[crazyhappygame]

Few notes about OpenAL.

1. OpenAL is licensed as LGPL (opens sourced only for MAC/iOS)
   https://github.com/cocos2d/cocos2d-x/blob/v3/docs/CODING_STYLE.md#legal-notice-and-author-line

The license must be compatible for the different App Stores, so GPL and LGPL code cannot be used in cocos2d-x.

2. OpenAL==native support for iOS/Mac only
   For Android https://developer.android.com/ndk/guides/audio
   below is recommended
   https://github.com/google/oboe

3. LGPL == problems
   We will have 3 *.so files (openal.so, mpg123.so, cocos2d-x.so) instead 1 *.so . Compilers are great with optimization and in-lining one binary. With 3 separate *.so files compilers can do nothing .....

[Volodymyr-13]

https://github.com/jarikomppa/soloud

[Xrysnow]

Some information I got:

1. OpenAL-soft is the most widely used OpenAL implementation. It‘s LGPL-licensed and can support all platforms we need. But on mac/ios we usually use the implementation provided by system.

2. To use OpenAL-soft on win/android/linux we just need one more dll/so file. It's easy and does not need too much work. Link to the library is permitted by LGPL license.

3. The MP3 format is too old and does not supported by all platforms in cocos now. Maybe we should turn to AAC or integrate a compact decoder like this one.

I highly recommond the audio engine of LÖVE to be a reference. It's clearly designed and has rich features. LÖVE is used by many games and can be considered stable.

If the audio engine of cocos does not want to provide too many features like LÖVE, I hope it can be designed like FileUtils to make developers extend it easily.

[crazyhappygame]

@Xrysnow

1. Mac/ios - agree OpenAL is perfect option with implementation provided by system. Best performance, compatibilty, no lgpl, no so
2. Linux - everything is better than property library fmod
3. Windows - ok
4. Android - I see couple problems
   4.1. OpenAL is not officially supported.
   4.2. OpenAL-soft does not support AAudio back-end - added in Android 8.0 better performance on 8.0+ devices
   4.3. LGPL
   4.4. Additional so files - Bigger app size, lower performance

Mp3 - works for me on Android/windows/ios. What is better format for multiplatform development?

[Xrysnow]

@crazyhappygame

1. Using OpenAL-soft on Android is not a problem, it has already been used by many apps.
2. Add a new backend for OpenAL-soft is not a hard work, I think it will be done in the future.
3. LGPL will not disturb you when you use the dynamic library.
4. libopenal.so only takes 260KB in the apk file, which is acceptable considering its benefits.

@Gary-Ash

Yes, this is a problem, but we can always use OpenAL-soft instead. Application in App Store using LGPL libraries is nothing new.

[halx99]

And recently, I wrote build guide for openal-soft & ogg & mpg123 with armv7,arm64: https://simdsoft.com/notes

[halx99]

The unified impmentation with few changes based on openal for all platforms is here:
https://github.com/simdsoft/x-studio/tree/master/cocos2d-x-patch/cocos/audio

[wbbtcool]

@halx99 Thank you for the examples. I integrated successfully. A problem was encountered at the time.
The volume of the mp3 played by the speaker is extremely low on Android, but the volume played by the
headphone is normal. Have you encountered this problem?
here ：https://github.com/kcat/openal-soft/issues/369

[halx99]

@halx99 Thank you for the examples. I integrated successfully. A problem was encountered at the time.
The volume of the mp3 played by the speaker is extremely low on Android, but the volume played by the
headphone is normal. Have you encountered this problem?
here ：https://github.com/kcat/openal-soft/issues/369

You are welcome, you can get help from the author of openal

[halx99]

Finished on engine-x
from the author of openal-soft, LGPL-2 library can free use as embedded dynamic framework on ios, and I post A pr to openal-soft to make it easy to build as ios dynamic framework: kcat/openal-soft#466

[wbbtcool]

@halx99

OpenAL is deprecated in favor of AVAudioEngine after iOS 13.

[halx99]

I finish replace apple openal with openal-soft, for more detail, please see: axmolengine/axmol#159

At engine-x, use pass cmake option BUILD_EXT_ALSOFT=ON, the deprecated wraning will gone

[wbbtcool]

@halx99 Awesome！Thank you very much！