Audio signal processor for generating a two-channel
audio signal, comprising: an input interface (100) for providing single-channel acoustic data describing an acoustic environment; a two-channel synthesizer( 200) for synthesizing two-channel acoustic data from the single-channel acoustic data using a listener position or rotation; and a sound generator (300) for generating the two-channel
audio signal from an
audio signal and the two-channel acoustic data, wherein the two-channel synthesizer (200) is configured to separate (210) the single-channel acoustic data into at least two parts consisting of a direct sound part and at least one of an early reflection part and a late
reverberation part, and to individually process (220, 230, 240) the at least two parts for generating two-channel acoustic data for each part, wherein the two-channel synthesizer (200) is configured to segment (231) the early reflection part into a plurality of segments, to determine (232) a plurality of image source positions representing source positions of reflection sound, to associate the image source positions to the segments using a matching operation, wherein the matching operation comprises calculating a time of sound arrival for each image source to the listener position and associating (234) the image source positions to corresponding segments that have
time delays in the corresponding segments
best matching with the time of sound arrival of the corresponding image source positions, and to calculate the two-channel acoustic data for the direct sound using the image source positions associated to the segments.