COMPASS: Coding and Multidirectional Parameterization of Ambisonic Sound Scenes

Abstract

Current methods for immersive playback of spatial sound content aim at flexibility in terms of encoding and decoding, abstracting the two from the recording or playback setup. Ambisonics constitutes such a method, that is however signal-independent, and at low spatial resolutions fails to provide appropriate spatialization cues to the listener, with potential severe colouration effects and localization ambiguity. We present a new signal-dependent method for parametric analysis and synthesis of ambisonic sound scenes that takes advantage of the flexibility of Ambisonics as a spatial audio format, while improving reproduction. The proposed approach considers a more general acoustic model than previous proposals, with multiple source signals and a non isotropic ambient component. According to a listening test using headphones, the method is perceived closer to binaural reference sound scenes than ambisonic playback.

Higher-Order Spatial Impulse Response Rendering: Investigating the Perceived Effects of Spherical Order, Dedicated Diffuse Rendering, and Frequency Resolution

“…Furthermore, since higher-order parametric processing has been shown to be advantageous for complex acoustic scenarios when using spherical harmonic signals as input [5][6][7], it is assumed that similar higher-order processing would also be beneficial for spatial RIRs. Therefore, a new higher-order formulation of the SIRR method is also presented in this article; and thus, an additional aim of this study was to ascertain the perceived effects of increasing the spherical harmonic input order when using this expanded formulation.…”

Signal Flow and Effects in Ambisonic Productions

“…Scenes [48]) by Archontis Politis can be seen as an extension of DirAC. In contrast to DirAC, it tries to detect and separate multiple direct sound sources from the ambient or background sound.…”

Ambisonic Coding with Spatial Image Correction

“…This method has been extended to High-Order Ambisonics (HOA) in HO-DirAC [9] where the sound field is divided into angular sectors; for each angular sector, one source is extracted. The recent COMPASS method [10] estimates the number of sources and derives a beamforming matrix by Principal Component Analysis (PCA) to extract sources. These approaches are efficient at low bitrates, but they have the disadvantage to reproduce only spatial cues, and not the original spatial image.…”