Comment 42 for bug 1742499

> Actually the mixxx VU meter cannot even distinguish a clipping signal from a signal which is properly levelled to ADC full scale both have samples with value 65535.

There are ways to detect clipping in the digital signal, but they are imperfect and computationally expensive. https://dsp.stackexchange.com/questions/65/what-are-good-ways-to-detect-signal-clipping-in-a-recording
Even if Mixxx does not attempt to detect a clipped input signal, a meter in Mixxx that is near the top could give a hint to check the sound card's input meter. If Mixxx does not attempt to detect a clipped input signal, then the input meter tooltips should explain this and so should the manual.