low-latency block based

the Fourier transform of a block of input signal, the two can be multiplied point

by point and the result transformed back to the time domain. As this kind of

processing is performed on successive blocks of the input signal, the output sig-

nal is obtained by overlapping and adding the partial results [65]. Thanks to

the FFT computation of the discrete Fourier transform, such technique can be

significantly faster. A drawback is that, in order to be operated in real time, a

block of N samples must be read and then processed while a second block is

being read. Therefore, the input-output latency in samples is twice the size of

a block, and this is not tolerable in practical real-time environments.

efficient yet low-latency solution [37, 64]. This third realization of convolution is

based on a decomposition of the impulse response into increasingly-large chunks.

The size of each chunk is twice the size of its predecessor, so that the latency of

prior computation can be occupied by the computations related to the following

impulse-response chunk. Details and discussion on convolution were presented

block-based FFT

algorithms based on feedback delay networks in many practical contexts. The

reasons are similar to those that make a CAD description of a scene preferable

to a still picture whenever several views have to be extracted or the environ-

ment has to be modified interactively. In fact, it is not easy to modify a room

impulse response to reflect some of the room attributes, e.g. its high-frequency

absorption, and it is even less obvious how to spatialize the echoes of the impulse

response in order to get a proper sense of envelopment. If the impulse response

is coming from a spatial rendering algorithm, such as ray tracing, these manip-

ulations can be operated at the level of room description, and the coefficients of

the room impulse response transmitted to the real-time convolver. In the low-

latency block based implementations of convolution, we can even have faster

update rates for the smaller early chunks of the impulse response, and slower

update rates for the reverberant tail. Still, continuous variations of the room

impulse response are easier to be rendered using a model of reverberation oper-

ating on a sample-by-sample basis.