VU meter

In plain words

A meter shows how loud a sound is right now. Green is fine, yellow is loud, red is about to distort. The little line that stays at the top for a moment is the latest peak.

rms, peak = engine.level()              # the master output, 0..1
ui.audio.VuMeter(level=[rms, peak])     # one bar per value

Levels and scale

level is one number or a list (one bar per channel), as linear amplitude from 0 to 1, which is what node.level() and engine.level() return. With scale="db" (the default) the meter shows it in decibels from floor (−60 dB) to 0 dB, as mixers do: quiet sounds still move it. scale="linear" shows the raw number (good for control signals).

Each channel holds its peak for hold seconds, then lets it fall.

Looks

variant	Looks like
"led"	Segments that light up (segments of them), dim when off.
"bar"	A smooth bar with the colors as a gradient.
"analog"	A needle VU meter (−20 to +3 VU) that moves with the ~300 ms ballistics of a real one.

colors is a palette name ("vu", "fl", "neon", "fire"… see Colors) or a list of colors from quiet to loud. vertical=False lays it out horizontally.

Property	Default	What it does
level	0	A level or a list of levels (0..1).
variant	"led"	"led", "bar" or "analog".
vertical	True	Direction of the bars.
length, thickness	160, 10	Size of each bar in pixels.
segments	24	LEDs per bar.
scale, floor	"db", -60	How a level maps to the meter.
hold	1.2	Seconds a peak is held.
colors	"vu"	A palette name or a list of colors.

Tip

Meters need to be redrawn every frame. Add pz.frames(lambda dt: None) to your app’s subscriptions() while the engine plays and read the levels in view().