資料壓縮技術對於聲音的系統是個必要的任務，它不只可以處理龐大的資料，但是也要求高品質的解析度。有一種聲音編碼的壓縮技術叫做MPEG，MPEG 是一個標準化對於聲音壓縮上是有效率的。它可以有意義的降低在頻寬傳送和資料儲存的需求上而且在失真率上也很低。 這篇論文所要呈現是一個新的低複雜度設計聲學模型，它的重要技術是應用於一個低功率的MPEG-2/4 AAC編碼器。在現今MPEG AAC的計算複雜很高，沒有辦法達到聲音即時播放，是攜帶式裝置的一個瓶頸。為了克服這個問題，必需對聲學模型做分析和最佳化的設計，所以，在演算法上，spreading function的計算方式是用查表方式來取代。除此之外，MDCT-Based 聲學模型也適合關於複雜度的降低和品質的保持，聲學模型的計算雜複度總共被降低到達到80%；在架構上，我們呈現一個專屬MDCT-Based聲學模型硬體設計，所以就可以實現一個即時播放在MPEG-2/4 AAC立體聲編碼器上，在位元速128kbit/sec下，頻率在20MHz都可以保持CD的品質。 Data compression technique is an essential task for audio systems, which not only handles enormous amounts of data, but also requires the high quality resolution. One of theses audio coding techniques, Moving Pictures Experts Group (MPEG) is powerful audio compression standardization. It can significantly reduce the requirements of transmission bandwidth and data storage, but with low distortion. The paper presents a new low complexity design of Psycho-Acoustic Model (PAM), which is the key technology for a low power MPEG-2/4 Advanced Audio Coding (AAC) encoding. The real-time constraint of MPEG AAC leads to a heavy computational bottleneck on today’s portable devices. To overcome this problem, design analysis and optimization of PAM are addressed. At algorithmic level, the calculation of spreading function was replaced with look-up tables. Besides, Modified-Discrete-Cosine-Transform-based (MDCT-based) PAM was referred to and adopted concerning reducing complexity and maintaining quality. The computational complexity of PAM could be reduced by more than 80% in total. At architectural level, we presented a dedicated hardware design of MDCT-based PAM. The proposed design could be implemented in a real-time MPEG-2/4 AAC stereo encoder at Low Complexity profile and at bitrate 128 kb/s below clock rate 20 MHz while maintaining CD quality.
