A Dedicated Decorrelator for Parametric Spatial Coding of Applause-like Audio Signals

Abstract

Parametric spatial coding of multichannel content has acquired widespread use in today’s audio codecs to enable efficient operation in the medium bitrate range. However, applause signals are still challenging to code with good perceptual quality using these techniques. To obtain a sufficiently low side information bitrate, the spatial parameter update rate is usually chosen in the range of several tens of milliseconds which is too low to restore a convincing spatial listener envelopment of applause-like signals. Moreover, state of the art decorrelators that are mandatory in parametric multichannel decoders inevitably deteriorate the signal quality of transient sound events, like handclaps, by dispersion. Therefore, we propose a novel decorrelation and parametrization technique for efficient coding of applause sounds: transient events are separated from the core decoder output and a dedicated decorrelator algorithm distributes the transients in the spatial image according to parametric guiding information transmitted in the bitstream. Listening tests show a substantial improvement in subjective quality compared to standard methods.