上小节我们讲解了：stream type, strategy, device, output, profile, module : policy，out flag的基本概念，理解了这些概念之后，我们就比较容易去分析代码了。
那么我们需要去分析那些代码呢？这些代码都在那些文件呢？该小节我们讲解以下所涉及的文件：
所涉及文件形象讲解
系统服务APP:
frameworks/av/media/mediaserver/main_mediaserver.cppAudioFlinger :
AudioFlinger.cpp (frameworks/av/services/audioflinger/AudioFlinger.cpp)
Threads.cpp (frameworks/av/services/audioflinger/Threads.cpp)
Tracks.cpp (frameworks/av/services/audioflinger/Tracks.cpp)
audio_hw_hal.cpp (hardware/libhardware_legacy/audio/Audio_hw_hal.cpp)
AudioHardware.cpp (device/friendly-arm/common/libaudio/AudioHardware.cpp)AudioPolicyService:
AudioPolicyService.cpp (frameworks/av/services/audiopolicy/AudioPolicyService.cpp)
AudioPolicyClientImpl.cpp (frameworks/av/services/audiopolicy/AudioPolicyClientImpl.cpp)
AudioPolicyInterfaceImpl.cpp(frameworks/av/services/audiopolicy/AudioPolicyInterfaceImpl.c