| Summary: | 碩士 === 國立中央大學 === 電機工程研究所 === 92 === 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.
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