package vimebac

Visual Metronome and Band Conductor

Vimebac is graphical metronome and instructions display that interfaces with JACK-midi applications. The display can be completely driven by MIDI events and it can also send MIDI events.

It can also be self-driven and hence run without jackd although this is somewhat less interesting since it becomes just a visual metronome.

The current features are:

• A visual metronome with arbitrary time-signatures.

• The display of arbitrary lines of text, e.g. to give instructions to the musician(s).

• Custom keyboard bindings to send arbitrary MIDI events.

Build

Simply:

jbuilder build vimebac.exe

Usage

See:

vimebac --help

You can always quit the application with Ctrl-Q.

Self-Driven Mode

Examples

Start at 106 beats per minute, the default time-signature is 4/4 showing also eighths:

vimebac self --bpm 106

Or with a slow, standard, 9/8 time-signature:

vimebac self --bpm 70 --beats 3 --subdivision 3

Keyboard Bindings

Then there are a few bindings that allow to modify the tempo:

• j → remove 1.

• k → add 1.

• h → remove 10.

• l → add 10.

And also to modify the font size:

• - → multiply by 0.9

• = → multiply by 1.1

Jack-Driven Mode

Example

Start and connect to Jack as vimebac-00:

vimebac jack --jack-name vimebac-00

You need then to connect the output of a MIDI-generating application into the vimebac-00:in.

MIDI Protocol

Vimebac operates the “channel” and the 2 “data-bytes” of any input MIDI event (resp. chan dat1, and dat2). For now it doesn't look at the “status.”

Here is how the values are interpreted (values not mentioned are ignored):

chan: 0            → beat_progress <- dat1 * 127 + dat2 / (127 ^ 2 + 127)
chan: 1            → bar_progress <- dat1 + (dat2 / 127)
chan: 2 && dat1: 0 → beat_on dat2
chan: 2 && dat1: 1 → beat_off
chan: 3            → bpm <- dat1 * 127 + dat2
chan: 4 && dat1: 0 → bar_structure.length <- dat2
chan: 4 && dat1: 1 → bar_structure.(dat2) <- Strong
chan: 4 && dat1: 2 → reset_bar_structure
chan: 5 && dat1: 0 → text_lines.(dat2) <- empty
chan: 6 or 7       → text_lines.(bits 6--3 of dat1)
                               .(bits 2--0 of dat1 ^ bits 6-4 of dat2)
                               .(if chan = 7 then (4 higher bits) else (4 lower bits)
                           <- bits 3--0 of dat2

where:

• beat_progress is the top progress bar (float in [0, 1]),

• bar_progress is the needle progress in beats (float in [0, 128]),

• beat_on <n> highlights the n-th bullet,

• beat_off turns off all bullet highlighting,

• bpm is the internal tempo (it is for display in jack-driven mode),

• bar_structure.length is the number of bullets, all “weak” by default,

• bar_structure.(<n>) is the n-th bullet (that can be set to “strong”),

• reset_bar_structure sets all the bullet to “weak.”

• text_lines is the array of lines to display.

Display Control

One can set all the geometry of the window with CLI options, for instance:

vimebac self --bpm 80 \
    --width 800 \
    --height 500 \
    --x-coord 250 \
    --y-coord 42

The relative size of the metronome Vs the text-area is set with --x-percent-metronome (percentage of the total width):

vimebac self --bpm 80 --x-perc 15

One can also set the initial size of the font (percentage of the total height):

vimebac self --text-size 25

The tempo display can be disabled:

vimebac self --hide-bpm