FFmpeg AAC decode PCM

1. Overview and flowchart

  1.1 AAC to PCM requires a decoding library to implement. Currently, there are three methods. Currently, the FFmpeg library is used for decoding.

    1) URL of faad decoding library: faad https://sourceforge.net/projects/faac/files/faad2-src/

    2) fdk-aac codec library URL:  fdk-aac