音频编码中MDCT算法的一种FPGA实现

Implementation of MDCT algorithm based on FPGA in audio coding

改进型的离散余弦变换(MDCT)在杜比AC-3音频压缩编码中起着时/频转换的作用,针对杜比AC-3中MDCT算法的要求,研究了一种易于FPGA实现的MDCT的硬件结构。考虑在实际应用中,编码器的计算速度是非常重要的,因此采用了N/4点FFT去作N点的MDCT,使运算量大大减少。充分利用FPGA的硬件资源,采用流水方式对数据实现MDCT运算,提高了系统的处理速度,减少了复杂逻辑,使计算、存储等操作协调一致。采用块浮点机制,动态扩大数据范围,在速度和精度之间得到折衷。整个设计划分成多个功能模块,全部采用Verilog HDL描述,实验结果表明,本方案是完全可以满足音频编码实时要求的。

The modified discrete cosine transform （MDCT） is implemented on Digital Audio Dolby AC-3 for time- frequency transform. To meet the demand of MDCT in Dolby AC-3 system, a method of realizing MDCT based on FPGA is introduced in this paper. In some practical applications, the computation speed of the coder is crucial. Therefore,we present a N/4 point FFT-based fast algorithm of MDCT. To use sufficiently hardware resource of the FPGA , the pipelined architecture is adopted to put the data into MDCT operation which reduce the complex logic and improve the processing speed and make the calculation and storage work harmoniously. By using block-float, the dynamic range of data is adaptively increased and the advantage of speed and precision is compromised. Each component is designed separately. An example demonstrates that the high-performance FPGA is suitable for real- time digital signal coding.