Erik Gosuinus Petrus Schuijers

Parametric coding of stereo audio

Parametric-stereo coding is a technique to efficiently code a stereo audio signal as a monaural signal plus a small amount of parametric overhead to describe the stereo image. The stereo properties are analyzed, encoded, and reinstated in a decoder according to spatial psychoacoustical principles. The monaural signal can be encoded using any (conventional) audio coder. Experiments show that the parameterized description of spatial properties enables a highly efficient, high-quality stereo audio representation.

Phantom Materialization: A Novel Method to Enhance Stereo Audio Reproduction on Headphones

Loudspeaker reproduction systems are subject to a compromise between spatial realism and cost. By simulating loudspeaker reproduction on headphones, the resulting spatial realism is limited accordingly, despite the virtually unlimited spatial imaging capabilities of binaural audio rendering technology. More particularly, phantom imaging as often used for stereo audio material intended for loudspeaker reproduction is subject to various restrictions in terms of loudspeaker positioning in simulated space. As a consequence, phantom imaging should preferably be avoided when simulating virtual loudspeakers over headphones, especially if head tracking is incorporated or if a wide sound stage is desired. A novel method is described to extract phantom sound sources from stereo audio content and convert these to sound sources in a virtual listening environment.

Audio coding based on frequency variations of sinusoidal components

Coding of an audio signal is provided where an indicator of the frequency variation of sinusoidal components of the signal is used in the tracking algorithm of a sinusoidal coder where sinusoidal parameters from appropriate sinusoids from consecutive segments are linked. By applying an indicator such as a warp factor or polynomial fitting, more accurate tracks are obtained. As a result, the sinusoids can be encoded more efficiently. Furthermore, a better audio quality can be obtained by improved phase continuation.

Converting decoded sub-band signal into a stereo signal

Synthesizing an output audio signal is provided on the basis of an input audio signal, the input audio signal comprising a plurality of input sub-band signals, wherein at least one input sub-band signal is transformed (T) from the sub-band domain to the frequency domain to obtain at least one respective transformed signal, wherein the at least one input sub-band signal is delayed and transformed (D, T) to obtain at least one respective transformed delayed signal, wherein at least two processed signals are derived (P)from the at least one transformed signal and the at least one transformed delayed signal, wherein the processed signals are inverse transformed (T−1) from the frequency domain to the sub-band domain to obtain respective processed sub-band signals, and wherein the output audio signal is synthesized from the processed sub-band signals.

Phantom materialization for headphone reproduction

Conventional stereo audio material is often produced using amplitude panning techniques to achieve flexible positioning of sound sources with a limited number of loudspeakers. Consequently, for faithful playback the orientation and position of the listener are very restricted. If stereo audio is reproduced over virtual loudspeakers on headphones incorporating head-tracking, these position and orientation restrictions limit the realism and spatial accuracy of the reproduction. In this paper, it will be outlined that amplitude panning and the corresponding phantom sound sources cause spatial quality limitations for headphone rendering. A novel method to circumvent phantom imaging on headphones is presented and evaluated in a listening test.