Abstract: A method of performing a convolution of an input data stream, the method comprising the steps of: (a) transforming an initial series of input data values into the frequency domain to form initial frequency domain data values; (b) multiplying the frequency domain data values with a set of coefficients so as to form convolved frequency data; (c) transforming the convolved frequency data into a spatial domain so as to form an initial series of output data values; (d) performing steps (a) to (c) on a subsequent series of input data values of the input data stream so as to form a subsequent series of output data values; the subsequent series of input data values overlapping the initial series of input data values; and (e) cross fading overlapping portions of the initial and subsequent output data values.

Abstract: A method of compressing an audio signal comprising a series of values is disclosed, the method comprising: utilising a predetermined maximum number of bits B for representing values; dividing the audio signal into a series of blocks of a predetermined length N; and for each of the blocks: computing the maximum number of bits b required to represent the values within a block; packing an indicator of b bits in an output stream; and for each value within the block: where the value exceeds 2B writing only the b most significant bits to the output stream; and where the value does not exceed 2B writing the value to the output stream. The aforementioned methods are well suited to compressing impulse response functions. There is also disclosed a method of decoding an audio signal encoded by the aforementioned methods.

Abstract: A sigma delta modulator apparatus comprising: input means for inputting a current input signal; differencing means for forming the difference between a current input signal and a current output signal; filtering means for filtering the difference so as to produce a filtered difference signal; and output means outputting a minimum or maximum output value so as to substantially minimize the filtered difference signal.

Abstract: A method for distribution multiple users of a soundfield having positional spatial components is disclosed including inputting a soundfield signal having the desired positional spatial components in a standard reference frame; applying at least one head related transfer function to each spatial component to produce a series of transmission signals; transmitting the transmission signals to the multiple users; for each of the multiple users, determining a current orientation of a current user and producing a current orientation signal indicative thereof; utilising the current orientation signal to mix the transmission signals so as to produce sound emission source output signals for playback to the user. The soundfield signal can comprise a B-format signal which is suitably processed.

Abstract: The invention relates to an apparatus for sound reproduction of a sound information signal having spatial components, the apparatus includes:sound input means adapted to input the sound information signal;headtracking means for tracking a current head orientation of a listener listening to the sound information signal via sound emission sources and to produce a corresponding head orientation signal;sound information rotation means connected to the sound input means and the headtracking means and adapted to rotate said sound information signal to a substantially opposite degree to the degree of orientation of said current head orientation of the listener to produce a rotated sound information signal; andsound conversion means connected to the sound information rotation means for converting the rotated sound information signal to corresponding sound emission signals for outputting by the sound emission sources such that the spatial components of the sound information signal are substantially maintained in the p