Signal processing device, control circuit, storage medium, and signal processing method

A control circuit to control a signal processing device, the control circuit causing the signal processing device to execute:

• performing window function processing on a Fourier transform frame cut from time-series signal data representing image information;
• transforming, into information in a frequency domain, the Fourier transform frame subjected to the window function processing;
• generating spectrogram data by converting a phase angle of a complex amplitude in the frequency domain into a hue and performing conversion that associates an absolute value of the complex amplitude with brightness by mapping that converts a distribution point of the complex amplitude in the frequency domain into a three-color value in a color space including three color components, the spectrogram data being defined so as to correspond to a two-dimensional plane of time and frequency;
• and
• performing processing to detect or identify a signal by convolutional processing and fully connected processing on the spectrogram data,
• wherein, in the conversion that associates the absolute value of the complex amplitude with the brightness, the generating spectrogram data includes applying a function that gradually decreases a slope of the absolute value of the complex amplitude.

A non-transitory storage medium to store a program for controlling a signal processing device, wherein

• the program causes the signal processing device to execute:
• performing window function processing on a Fourier transform frame cut from time-series signal data representing image information;
• transforming, into information in a frequency domain, the Fourier transform frame subjected to the window function processing;
• generating spectrogram data by converting a phase angle of a complex amplitude in the frequency domain into a hue and performing conversion that associates an absolute value of the complex amplitude with brightness by mapping that converts a distribution point of the complex amplitude in the frequency domain into a three-color value in a color space including three color components, the spectrogram data being defined so as to correspond to a two-dimensional plane of time and frequency;
• and
• performing processing to detect or identify a signal by convolutional processing and fully connected processing on the spectrogram data,
• wherein, in the conversion that associates the absolute value of the complex amplitude with the brightness, the generating spectrogram data includes applying a function that gradually decreases a slope of the absolute value of the complex amplitude.

A signal processing method to be executed by a signal processing device, the signal processing method comprising:

• performing window function processing on a Fourier transform frame cut from time-series signal data representing image information;
• transforming, into information in a frequency domain, the Fourier transform frame subjected to the window function processing;
• generating spectrogram data by converting a phase angle of a complex amplitude in the frequency domain into a hue and performing conversion that associates an absolute value of the complex amplitude with brightness by mapping that converts a distribution point of the complex amplitude in the frequency domain into a three-color value in a color space including three color components, the spectrogram data being defined so as to correspond to a two-dimensional plane of time and frequency;
• and
• performing processing to detect or identify a signal by convolutional processing and fully connected processing on the spectrogram data,
• wherein, in the conversion that associates the absolute value of the complex amplitude with the brightness, the generating spectrogram data includes applying a function that gradually decreases a slope of the absolute value of the complex amplitude.