WaveWarp 2.0 Component
      
Multirate:
Functional Description
Reduces the sample rate of the input by an integer factor, M, with
a built-in FIR anti-aliasing filter.
The output sample rate is a factor of M lower than the
input sample rate.
Separate components are provided for 2, 3, and M (flexible) downsampling
factors.
Algorithm
In the current implementation, the FIR low-pass
anti-aliasing filters are
designed according to
"hard-wired" specifications
(i.e. the specifications cannot be changed by the user).
These are summarised as follows (refer to the low-pass
filters in the
Digital Filters
category of the Component Library for an explanation of terminology):
Blackman windowed design with a pass-band gain of
-0.5 dB, a stop-band gain of -85 dB, a pass-band edge frequency of
Fs/2.2M (where Fs is the input sample rate
of the downsampler), and a stop-band edge frequency of
Fs/1.8M. These specifications are found to yield filters
with reasonable performance.
The real-time filter output is computed by
direct convolution.
The downsampler is implemented in the direct form: first
the input data is filtered (with the filter running at the high
sample rate), then the filtered signal is downsampled (by retaining only
every Mth sample).
See
[CrRa]
and
[StNg]
for a detailed treatment
of multirate signal processing.
For a specific discussion
on downsampling by an integer factor, see
section 2.3.2 of
[CrRa]
and chapters 1 & 3 of
[StNg].
Signal Implementations
| Audio signals | Control signals | Description |
|---|
| Single input mono single output mono | n/a | Converts the sample rate of the mono signal |
| Single input stereo single output stereo | n/a | Converts the sample rate of the stereo signal |
Related components:
Example DrawingBoards illustrating usage:
|
