Cascaded trellis-based rate-distortion control algorithm for MPEG-4 advanced audio coding

In this paper, a few low-complexity and high-performance rate-distortion control algorithms for MPEG-4 Advanced Audio Coding (AAC) are proposed. One key element in producing good quality compressed audio particularly at medium and low rates is a high performance rate-distortion controller in the audio encoder. Although the trellis-based rate-distortion control algorithms previously proposed can achieve a praiseworthy performance, their computational complexity is extremely high. Therefore, for practical applications, it is very desirable to achieve a similar performance at a much lower complexity. Two types of techniques are proposed in this paper to reduce the computational burden of the trellis-based algorithms. One is splitting a very heavy calculation stage into two sequential steps with much less computation. The other is reducing the candidates in the trellis for parameter search. Together, when applicable, our approach achieves a similar coding performance (audio quality) but requires less than 1/1000 complexity in computation.