MP31編碼器在嵌入式Linux上的實作與效能實作

Abstract

MP3是現今最流行的音樂檔案格式，隨著各式各樣的行動裝置出現，MP3不只是能在電腦上播放與壓縮，播放MP3的產品在日常生活中已是隨處可見的數位產品，而具有將音樂壓縮編碼成MP3的消費性電子產品也因嵌入式系統的日益發達而有了更多的發揮空間。 本論文將一套開放原始碼的MP3 編碼器從PC 上實作到嵌入式系統上，利用Linux當作嵌入式系統的作業系統，主要以定點數取代浮點數運算的方法來加快執行速度，附帶進行數學函式的化簡，簡化analysis filter的演算法和去掉aliasing reduction，使執行更快速。本論文著重在加速的方法與得到的效能改進，所得聲音因加速處理而稍微有些雜訊不是此論文重點。最後把加速前後的速度作一比較。

MP3 is now the most popular music format. With the appearance of various mobile devices, MP3 is not only played and compressed on the computer. The digital products which played MP3 have been everywhere in the daily life. Because of the development of the embedded system, the commercial electronic products which used in music compress encoding can make further progress. This thesis implements an open source MP3 Encoder on an embedded system. With Linux as the operating system in the embedded system, the fixed point operation is used to increase the executing speed. Besides, the simplification of math functions and algorithms of analysis filter and the reduction of aliasing reduction are also applied to accelerate further. This thesis focuses on the method of speeding up the program in the embedded system. The noise of sound caused by acceleration is not a key point of this thesis. Finally, I will compare the results before and after the acceleration..