  The paper presents a method for improving spatial resolution of first-order
ambisonic audio. The method is based on time/frequency decomposition of the
audio with subsequent extraction of a directed plane wave from each frequency
component. The method develops the basic ideas of high angular resolution
planewave expansion (HARPEX) and directional audio coding (DirAC) taking
advantage of real-valued sparse decomposition. Real-valued frequency components
as opposed to complex-valued introduce simpler and more stable direction of
arrival estimates, while sparse decomposition introduces an accurate and
unified approach to describing sounds of different nature from transient to
tonal sounds.
