QwtPlotSpectrogram: how to render only last line of spectrogram image

Hello.

I have wrote simple program that captures data from soundcard, processes it (compute FFT) and plot computed data as waterfall using QwtPlotSpectrogram. Everything works fine but this program uses a lot of CPU resources, and more specifically - rendering entire spectrogram image stress CPU.

I wonder if it is possible to render only the last line of the spectrogram and to add it to an existing image (and then remove the oldest spectrogram line).

Could You give me some tips how to save some CPU resources.

Thanks.

Check the archive of this forum - there is already a thread about a waterfall plot. When you have read it continue here.

Uwe