Parametric Stereo

Abstract: In 2004 the ISO/MPEG Audio standardization group started a new work item on efficient and backward-compatible coding of high-quality multichannel sound using parametric coding techniques. Finalized in the fall of 2006, the resulting MPEG Surround specification allows the transmission of surround sound at bit rates that have been commonly used for coding of mono or stereo sound. The results of the standardization process are summarized by describing the underlying ideas and providing an overview of the MPEG Surround technology. The performance of the scheme is characterized by the results of recent verification tests. These tests include several operation modes as they would be used in typical application scenarios to introduce multichannel audio into existing audio services.

Abstract: Parametric stereo coding is a technique to efficiently code a stereo audio signal as a monaural signal plus a small amount of stereo parameters. The monaural signal can be encoded using any audio coder. The stereo parameters can be embedded in the ancillary part of the mono bit stream creating backwards mono compatibility. In the decoder, first the monaural signal is decoded after which the stereo signal is reconstructed from the stereo parameters. In this paper, a low complexity decoder solution is described based on complex-modulated filter banks. Combinations of the parametric stereo decoder with both a parametric coding scheme and with aacPlus will be elucidated.

Abstract: Compared to traditional waveform coding standards that employ subband or transform coding, parametric coding is regarded as a technique that allows even further reduction of bit rates. In response to a call for proposals by MPEG-4 in January 2001, Philips submitted a parametric coder targetting at a high quality level. Currently, this coder is improved in the course of the “MPEG-4 Extension 2” standardisation process. Recently, two enhancements have been made increasing the overall performance of the coder. These consist of an improved model for the noise object and a parametric stereo extension.