Minor Spectroid bug: the plot and spectrogram displays some gaps

[Guillermo Luijk]

Spectroid is a great app, but it seems to have a minor (but uncomfortable) bug: it often produces some gaps at particular frequencies which mean the curve shows some cuts, and black stripes appearing in the spectrogram. See here:

http://guillermoluijk.com/datosimagensonido/fftlavadora1.png

Gaps around 48Hz and 95Hz.

Current config.:

Audio source: default

Sampling rate: 48000Hz

FFT size: 1024 bins (47Hz/bin)

Decimations: 8 (0,18Hz/bin @ DC)

Window function: Blackman-Harris

Desired transform interval: 20ms (50Hz)

Exponential smoothing factor: 0,30

Freq axis scale: Linear

Waterfall: 2/3 screen

Max-hlold trace: ON

Peak markers: 1 marker

Regards

[Carl Reinke]

It's not a bug; it's intentional.  Spectroid uses multiple FFTs in order to provide finer frequency resolution at lower frequencies, but that results in discontinuities in the spectrum (which appear as gaps).  You can configure it to use only one FFT by setting "Decimations" to "0", but the results don't look great on a logarithmic scale.

--Carl

[Guillermo Luijk]

Thanks Carl, I understand now the reason for the gaps, but still don't grasp what's the usefulness or convenience of showing them in the Spectrogram. They make the graph misleading and don't contribute in any positive way. If the values are missing, they could be replicated or averaged from the available neighbour values.

Regards