[FFmpeg-user] 'showspectrumpic' filter: scaling of the frequency axis and fft windows size

[Wolfgang Hugemann]

Today, I have been experimenting with the 'showspectrum' filter, mostly
with 'showspectrumpic'.

I think there is a bug in the log scaling of the frequency axis if (and
only if) it doesn't start at zero: The ratios of the frequency axis'
labelings is not constant, they grow with larger values.

I had a quick look at the source code and gained the impression that the
fft windows size is based on the height of video created (?). At least
it cannot by specified in the filter options.

Kind regards
Wolfgang Hugemann