--chanmask=0x63f
Perhaps, it could be a different (but possibly novel) way to visualize stereo audio spectrum (higher amplitude on one graph than other means closer to 90 degrees out-of-phase on certain frequencies, as opposed to full 180 degrees out-of-phase as in traditional L/R spectrum analyzers), where two differently-colored graphs represent magnitude part of complex-valued FFT; the first one is as it is, and the second one is same as the first, but the order is flipped since the input to the FFT data is complex-valued, thus not symmetric in the full FFT output and to be able to visualize complex-input FFTs with the frequency range of 20Hz to 20kHz and a logarithmic frequency scaleAlso, I think this topic is little bit de-railed; it went into performance improvements of multichannel audio spectrum analyzers by using complex-input FFTs, which is true considering calculating two or more FFTs can have significant performance impact. But what I really mean is that is complex-input FFT as in spectrum of I/Q signals in SDR really useful for analysis of stereo audio, which is basically the same minus the "unscrambling" operation?
I don't see any reason you would want the scrambled output when you could have the regular unscrambled one instead.