在MPEG/Audio上資料隱藏方法之研究與使用ADSP-2181數位訊號處理器實現資料隱藏解碼器

Abstract

本論文提出把資料嵌入MPEG/Audio裡的方法與實作。資料嵌入MP3的目的是為了增加MP3的用途與功能性，也可以提供音樂公司對消費者的額外服務，如在MP3中加入歌詞同步顯示、歌手照片或是消費者的基本資訊等等。本論文中的資料嵌入方法可分為資料嵌入編碼器和解碼器：資料嵌入編碼器是在電腦上實現，主要是把資料嵌入到MP3音框的三個比較不重要的區塊裡，對音樂本身的音質較無影響。而這三個區塊分別是big value區塊中10KHz以上的符號位元、count1區塊中的符號位元和bit reservoir中用不到的位元。資料嵌入解碼器是在ADSP-2181數位訊號處理器上實現，主要是做資料的擷取並做分析，並做歌詞和圖片的同步顯示。此包含資料嵌入解碼器的MP3解碼器在ADSP-2181上使用了20.7Kbytes的程式記憶體和23.6Kbytes的資料記憶體，並且在18MIPS就可達到即時播放的速度，約佔此晶片55%的運算能力。此資料嵌入的方法亦可應用到MPEG-2/Audio AAC或是MEPG-4/Audio AAC裡，並不只侷限於使用在MP3演算法上。

In this thesis the method and implementation of embedding data into MPEG/Audio will be discussed. The purpose of embedding data into MP3 is to add applications and functions of MP3, as well as to facilitate the music company to provide additional service to customers, for example, adding pictures of singers, background information or lyrics into MP3 for synchronous display. Data embedded encoder and decoder will be introduced in this thesis. The data embedded encoder, implemented on PC, is to embed data into three less important music regions in MP3, causing less influence to the quality of music. These three music regions are: sign bites which exceed 10 KHz in big value region, sign bites in count1 region, and unused bites in bit reservoir region. Data embedded decoder, ported on ADSP-2181 DSP processor, is to catch data for analyzing and executing synchronous display of lyrics and pictures. The MP3 data decoder in ADSP-2181 uses 20.7Kbytes of program memories and 23.6Kbytes of data memories, and will accomplish real-time playing in 18MIPS, occupying about 55% processing power of the DSP. This approach can be applied in MPEG.-2/Audio ACC or MPEG-4/Audio ACC as well, not only in MP3 algorithm.