UPnP DeviceArchitecture v1.0 Specification to build UPnP compatible devices and control points.

音频处理的代码，主要是架构的代码，有if，id，ex，ma，wb等5个阶段的代码，也有ctrl等控制代码-Audio processing code, the main structure of the code is there if, id, ex, ma, wb, etc. 5 stages of the code, but also ctrl control code, etc.

document for voip system arch