Home // International Journal On Advances in Intelligent Systems, volume 4, numbers 3 and 4, 2011 // View article
Authors:
Wolfgang Fohl
Jürgen Reichardt
Jan Kuhr
Keywords: Mixed-reality audio; realtime HRTF interpolation; filter decomposition; system-on-chip.
Abstract:
A system-on-chip platform for realtime rendering of spatial audio signals is presented. The system is based on a Xilinx Virtex-6 FPGA platform. On the chip an embedded WFublaze{} microprocessor core and FIR filters are configured. Filtering is carried out in the FPGA hardware for performance reasons whereas the signal management is performed on the embedded processor. The azimuth and elevation angles of a virtual audio source relative to the listener's head can be modified in real time. The system is equipped with a compass sensor to track the head orientation. This data is used to transform the room related coordinates of the virtual audio source to the head related coordinates of the listener, so that a fixed position of the virtual sound source relative to the room can be attained regardless of the listener's head rotation. Head related transfer functions (HRTF) were sampled in steps of 30° for azimuth and elevation. Interpolation for intermediate angles is done by either interpolating between the coefficients of the measured HRTFs at the four adjacent angles (azimuth and elevation), or by feeding the audio signal through the corresponding four filters, and mixing the outputs together. In the latter case the required four filter processes per output stereo channel do not result in longer computing time because of the true parallel operation of the FPGA system. In order to achieve a constant loudness level for all interpolated angles it is necessary to decompose the HRTF filters in two components, one for the amplitude response and the other for the delay. The system output is identical to the output of a corresponding Matlab prototype.
Pages: 309 to 317
Copyright: Copyright (c) to authors, 2011. Used with permission.
Publication date: April 30, 2012
Published in: journal
ISSN: 1942-2679