HDTV音频解码综合滤波器组算法优化及FPGA实现

Optimized algorithm for synthesis filter banks in HDTV audio decoding and implementation on FPGA

在HDTV音频(AC-3,MPEG-2)解码中均采用了综合滤波器组(IMDCT)实现时频变换,它们的共同点是其长度N是4的整数倍,而且其结构具有很好的对称性。本文推导出了用两个N/4点的DCT-Ⅱ来实现N点的IMDCT的优化算法。该优化算法可以得出MDCT和IMDCT拥有共同的转换核,使得MDCT和IMDCT可以共用一个统一的结构,节省了硬件开销。可以有效的应用于MDCT和IMDCT的并行VLSI结构。本文以AC-3标准为例,在FPGA上实现了其256点IMDCT单元,结果表明该算法减少了运算次数,降低了复杂度,提高了运算速度。

Synthesis Filter Banks is adopted in HDTV Audio（AC-3, MPEG-2） decoding and it implements the time- frequency transformation. The length of inverse modified discrete cosine transform （IMDCT） is integer times of 4 and its structure has a good symmetry. This paper deduces an optimized algorithm for the IMDCT. The type of two N/4 point DCT-Ⅱs is adopted in the algorithm and the algorithm includes a common transformation kernel in the MDCT and IMDCT. So the unit of MDCT and IMDCT can use a unified structure and it saves the hardware resource. It can be used in the parallel VLSI structure of MDCT and IMDCT. A 256-point IMDCT in AC-3 has been realized on FPGA in this paper. The times of computation and the complexity of the algorithm are reduced, the computing speed is increased.