Efficient implementation of a class of MDCT/IMDCT filterbanks for speech and audio coding applications

Abstract

In this paper, an efficient algorithm for implementing MDCT/IMDCT of lengths 5 2Transforms for such lengths are of interest for speech and audio coding applications, such as recently issued and/or emerging standards G.729.1, G.EV-VBR, and EVRC-WB. In our design we utilize a mapping of MDCT of size N into N/2-point DCT-IV and DCT-II with isolated premultiplications, which are subsequently moved in the windowing stage. We show that such a modified window is piece-wise symmetric, and can be stored using N/2 words. In our algorithm we also use an efficient factorization of 5-point DCT-II which requires only 4 multiplications by irrational factors. We compare our proposed algorithm with several alternative implementations and show that our design offers practically appreciable reduction in complexity and memory usage.

Efficient algorithms for MPEG-4 AAC-ELD, AAC-LD and AAC-LC filterbanks

“…The remaining even length DCT can be optimally implemented by decimation process described in [12]. This overall scheme leads to a very efficient MDCT implementation, see [13] for additional details.…”

A New Decomposition Algorithm of DCT-IV/DST-IV for Realizing Fast IMDCT Computation

“…A radix-3 algorithm for efficiently computing the MDCT/ IMDCT of a sequence with length was presented in [16]. Recently an efficient algorithm for implementing MDCT/ IMDCT of transform block lengths was developed in [17].…”

Relationship between DCT-II, DCT-VI, and DST-VII transforms

“…The DCT-IV is used in audio coding algorithms, such as ITU-T Rec. G.722.1, MPEG-4 AAC, and others [2]. Such transforms are very well studied, and a number of efficient technique ex ists for their computation [1,3,4,5,6,7].…”