Metering – Apple Logic Pro 7.2 User Manual
Page 249
Appendix B
Logic Control—MIDI Implementation
249
Metering
Received:
D0, XX
Peak level
<Hdr>, 20, ii, mm, F7
Channel meter mode
<Hdr>, 21, yy, F7
Global LCD meter mode
Transmitted:
None
XX
Meter
level
in
the
form
of
(0
h
h
h
l
l
l
l):
hh
Channel to be addressed (0 thru 7)
ll
Meter
level:
0
thru
C =
level
meter
0%
to
100%
Overload not cleared!
E =
set
overload
F =
clear
overload
ii
Channel ID (0 to 7)
mm
mode
bit
map
in
the
form
of
(0
0
0
0
0
l
p
s):
l
Enable level meter on LCD
p
Enable peak hold display (horizontal only)
s
Enable Signal LED
yy
00 = horizontal; 01 = vertical
Notes:
Â
There
is
only
one
level
meter
per
channel.
For
stereo
tracks,
use
the
maximum
of
left
and
right
levels.
Â
Only
transmit
peak
levels.
Logic
Control
automatically
decreases
the
level
meter
bars,
and
switches
off
the
Signal
Present
LED
(over
time).
This
approach
ensures
that
MIDI
bandwidth
takes
only
a
fraction
of
that
required
by
implementations
where
the
current
level
(and
peak
level)
is
transmitted
constantly.
Â
Decay
rate
is
approximately
300ms
per
meter
division
(1.8
seconds
to
fall
from
100%
to
0%).
Â
The
LCD
meter
value
and
the
duration
of
the
Signal
Present
LED
are
controlled
by
the
same
data
byte.
Â
While
the
LCD
switches
between
horizontal
and
vertical
metering
mode,
it
ignores
LCD
messages.
You
should
delay
LCD
messages
for
at
least
600
ms
after
sending
an
LCD
metering
mode
change
message.