My modifications to spectrogram.c to plot frequency on log axis and also to limit upper and lower plotted frequency are close to being complete.
I'm not very familiar with sox, and my C a bit rusty, so if any seasoned sox developers have the time to review my code, that would be great. The log axis on its own didn't require much code change, but I found the frequency limits needed a fair bit of new parsing code. Specifying frequency limits (at least a lower bound) is necessary in log plots else a good part of the screen will be wasted in frequencies 1 - 100 Hz which is not the most useful for audio.
I've documented the changes at this blog post:
And the code is here:
If this code is worth contributing please advise what are the next steps (if any). Consider this code contributed under whatever terms that are required to have it added to the project.
Regards,
Joe Desbonnet.