参数音频编码回顾

The Review of Parametric Audio Coding

音频编码主要有两类技术:波形编码,参数编码。前者适合高速率高质量的应用环境,后者适合带宽受限或存储容量受限的应用或环境。参数音频编码以源模型表示信号,运用基于心理声学原理的参数估计和量化方法,提取、量化感知重要的源模型参数,在保证重建信号质量的同时,有效减小了编码比特率。近年来,研究者将自适应时间分段、联合参数量化、参数立体声等新技术引入参数音频编码,使算法得到了优化,重建信号质量也得到了显著提升,其中某些技术还成为了国际标准,并获得商业应用。本文回顾了近十几年来参数音频编码的重要进展,评述、探讨了存在的问题和研究的难点,并给出了两个典型参数音频编码系统的主观测试数据,以定量显示其性能,最后,展望了参数音频编码发展的方向。

There are two basic techniques in audio coding：waveform coding and parametric coding.The first one is usually utilized in high rates and high quality coding applications,the last one utilized in bandwidth or storage capacity constrained applications and fields.Parametric audio coding decomposes source signal into several components by source models,and employs parameter estimation /quantization algorithms that based on psychoacoustic model,to extract model parameters and then quantize these parameters.These algorithms reduce the bit rate and preserve the quality of reconstructed signal.In recent years,some new techniques have been proposed, such as adaptive time segmentation,joint parameter quantization,parametric stereo,which optimize the coding algorithms and enhance the quality of reconstructed signal significantly.As a result,some of the schemes have now become international standards and have being used in commercial products.In the paper,an overview on the important advances of parametric audio coding in the past decades is introduced.While reviewing the aspects that should be improved,the existing difficult problems in parametric audio coding are discussed.Furthermore,the results of listening tests are presented for two special parameter audio coders in order to illustrate the performance of these techniques.In the end,possible directions of further improvements are indicated.