1. Digital filters (What is digital filter, and what is filter realization)
http://en.wikipedia.org/wiki/Digital_filter
2. FIR (Window design method)
http://en.wikipedia.org/wiki/Finite_impulse_response
3. Fourier analysis
http://blog.youkuaiyun.com/dznlong/category/383066.aspx
http://www.dspguide.com/pdfbook.htm
http://en.wikipedia.org/wiki/Fourier_Analysis
4. Transfer function
http://en.wikipedia.org/wiki/Transfer_function
5. Polyphase filter
http://www.edaboard.com/ftopic64246.html
6. Window Function (including MDCT)
http://en.wikipedia.org/wiki/Modified_discrete_cosine_transform
http://en.wikipedia.org/wiki/Window_function
7. MP3: The Definitive Guide
http://oreilly.com/catalog/mp3/chapter/ch02.html
8. FT的局限性和窗函数对其局限性的弥补
http://pst.nst.pku.edu.cn/teaching/nuclear_medicine/DIPnotes/chapter3/chapter3_2.pdf