Spectrogram contrast

[ik1qfk]

Hello everyone,
I am the creator of the website www.vlf.it, and I am dealing with radio signals of natural origin and seismic precursors radio. I just discovered Sonic Visualizer and I am very impressed: it is a good tool for the analysis and study of the signals.

But I am not able to do one thing: as I do to increase the contrast in the spectrogram? The color palette is distributed over the entire dynamic of the signal (90 dB if the file is 16-bit). As you set to ensure that the color range is spread for example on only 30 dB? I found the volume control but that moves the palette up or down, it does not change the extension.

Thanks, Renato

[mark_orion]

Hello Renato,

good to see another "ELF" person in this forum! I actually came across your site before and find it very interesting - thanks! I think what you are asking for is not possible with the current release of Sonic Visualizer, but maybe a future version or an update of one of the analysis VAMP plugins will provide it. ELF was actually what brought me to Sonic Visualizer as well - less from my own interest in amateur radio and astronomy but more from being one of those who can hear what the press often calls "the hum".
Here is another program that you might know: http://freenet-homepage.de/dl4yhf/spectra1.html
This program can do a lot of live DSP tasks - including various kinds of spectral analysis and signal decoding. Although it is a Windows program you can run it under Linux by using "wine". I even got it to work with Jack so I was able to use my Presonus Firebox with 96Khz sampling rate as input.

vy73 Mark

[cannam]

Thanks for the comments.  No, I'm afraid there is no direct way to clamp the colour range of the spectrogram to a subset of the available dynamic range.  You can of course do various things to change the palette's effective brightness (level control) or distribution (e.g. set colour scale to linear and use the high-gain palette) but you cannot currently set the dynamic range extents.

On the subject of other spectral visualisers, especially for live monitoring, I'd like to mention baudline (http://www.baudline.com/) -- no doubt you know it already, but I think it's worth noting in the topic.


Chris

[ik1qfk]

Thanks for your info.

I know baudline but I'm a (happy) windows user. I also know SpectrumLab because Wolf (DL4YHF developer) is my friend (I am also one of the software debugger). I was looking for an alternative for the analysis of wave files. SpectrumLab is the best software for direct processing, but it has some gaps on the recording files post processing.

Bye, Renato