Experimental study on improved parametric stereo for bit rate scalable audio coding

Abstract

This paper presents an experimental study on generalizing Parametric Stereo (PS) technique in an attempt to make it scalable for low and high bit rate implementations which are very useful for various internet services. As specified in the MPEG standard, PS is only intended for applications at a stereo bit rate of 24 kb/s. If operated at higher bit rates, PS would have much worse performance than other audio codecs such as MPEG-1/2 Layer 3 (MP3) and MPEG Advanced Audio Coding (AAC). To improve performance at higher bit rates, the proposed Improved PS transmits residual signal. However, the bit rates of the down-mix and residual signals have to be selected properly to achieve optimal performance. The results of the experiments show that performance of the Improved PS, in terms of objective difference grade (ODG), significantly improves as the bit rate increases. Testing objectively using 5 different critical audio materials, Improved PS consistently outperforms AAC Stereo at a bit rate of 128 kb/s.