Encapsule Audio Engine implementation for the platforms using OpenAL

[dumganhar]

Currently, new AudioEngine uses the following technique:

• Android: OpenSLES
• Windows / Mac / iOS: OpenAL
• Linux: fmod --> could be replaced with OpenAL too.
• Tizen: platform depended SDK

Except Android and Tizen, other platforms could all use OpenAL. But now, we have separated folder for platforms using OpenAL, the bad thing is although they all use OpenAL , the source code are so different. :(

Perhaps, we need to encapsule this and only need cocos/audio/openal for these platforms that use OpenAL. In this way, it will be better for maintaining and better for adding new features.

Some folder structure may be like this:

cocos/audio/openal/AudioEngine-impl.cpp
cocos/audio/openal/AudioEngine-impl.h
cocos/audio/openal/PlatformSpecific.h
cocos/audio/openal/PlatformSpecific-win32.cpp
cocos/audio/openal/PlatformSpecific-osx.cpp
cocos/audio/openal/PlatformSpecific-ios.cpp
cocos/audio/openal/PlatformSpecific-linux.cpp
cocos/audio/openal/PlatformSpecific-winrt.cpp

Why Should We Need Specific?

Although they all use OpenAL to play sound, they should use platform dependence code to decode compressed file (.mp3/.ogg/.caf) into pcm buffer.

Any idea? @ricardoquesada @minggo .

[minggo]

@dumganhar i think you can refer to EditBox, please use the same rule as others.

[dumganhar]

Good point. :)

[halx99]

I think the original design: AudioDecoderManager + AudioDecoder is good for multi-platforms diff implement to decode mp3,ogg,etc..

[halx99]

@dumganhar By the way, the previously implement of Audio Engine doesn't support .ogg at Apple platforms, If you Refactor the audio engine, you can think to simply import vorbis libs to Apple xcode project.