This node converts signals of frequency domain into waveforms of time domain.
No files are required.
This node is used to convert signals of frequency domain into waveforms of time domain.
When to use
Parameter name |
Type |
Default value |
Unit |
Description |
LENGTH |
512 |
[pt] |
FFT length |
|
ADVANCE |
160 |
[pt] |
Shift length |
|
SAMPLING_RATE |
16000 |
[Hz] |
Sampling rate |
|
MIN_FREQUENCY |
125 |
[Hz] |
Minimum frequency |
|
MAX_FREQUENCY |
7900 |
[Hz] |
Maximum frequency |
|
WINDOW |
HAMMING |
Window function |
||
OUTPUT_GAIN |
1.0 |
Output gain |
Input
: Map<int, ObjectRef> type. ObjectRef is Vector<complex<float> > .
Output
: Map<int, ObjectRef> type. ObjectRef is Vector<float> .
Parameter
FFT length; must be equal to the other node (MultiFFT ).
Shift length; must be equal to the other node (MultiFFT ).
Sampling rate; must be equal to the other nodes.
The minimum frequency used for waveform generation
The maximum frequency used for waveform generation
Window function. Select HAMMING, RECTANGLE or CONJ
Output gain
Inverse FFT is performed on four low bands of the input signals of the frequency domain by substituting 0 for frequency bins over $\omega _ s/2-100$ [Hz]. A designated window is adopted for overlap-add processing, a method of reducing the influence of a window by performing inverse transformation for every frame, adding the signals for which the time domains are shifted back while shifting them. For details, see the web pages in References. Finally, the temporal waveforms are multiplied by the output gain and output. Further, subsequent frames must be read for overlap-add processing; therefore, this node delays the entire processor. The length of the delay can be calculated as:
\begin{equation} delay = \left\{ \begin{array}{@{\, }ll} \left| \mathrm{LENGTH}/\mathrm{ADVANCE} \right|- 1,& {if~ ~ } \mathrm{LENGTH} \, mod\, \mathrm{ADVANCE} \ne 0,\\ \mathrm{LENGTH}/\mathrm{ADVANCE}, & {otherwise}. \end{array} \right. \end{equation} | (143) |
Since the default values for HARK are LENGTH = 512 and ADVANCE = 160, the delay is three frames, which resulting in a 30 [ms] delay for the entire system.
(1) http://en.wikipedia.org/wiki/Overlap-add