SPEAKER(4) | Device Drivers Manual | SPEAKER(4) |
speaker
— console
speaker audio device driver
spkr* at pcppi?
spkr* at audio?
#include <dev/spkrio.h>
The speaker device driver allows applications to control the console speaker on machines with a PC-like 8253 timer implementation or a synthesized speaker from an audio device/soundcard.
Only one process may have this device open at any given
time; open(2) and
close(2) are used to lock and
relinquish it. An attempt to
open(2) when another process has
the device locked will return -1 with an EBUSY
error
indication. Writes to the device are interpreted as “play
strings” in a simple ASCII melody notation. An
ioctl
() for
tone generation at arbitrary frequencies is also supported.
For the pcppi(4) device sound-generation does not monopolize the processor; in fact, the driver spends most of its time sleeping while the PC hardware is emitting tones. Other processes may emit beeps while the driver is running.
For the audio device speaker, the speaker uses one of the virtual audio channels. Enabling this device will also provide a wsbell(4) keyboard bell.
Applications may call
ioctl
() on
a speaker file descriptor to control the speaker driver directly;
definitions for the ioctl
() interface are in
<dev/spkrio.h>
.
The tone_t structure is as follows:
typedef struct { int frequency; /* in hertz */ int duration; /* in 1/100ths of a second */ } tone_t;
A frequency of zero is interpreted as a rest.
At present there are four ioctls:
SPKRGETVOL
SPKRSETVOL
SPKRTONE
SPKRTUNE
The play string language is modelled on the
PLAY
statement conventions of IBM BASIC
2.0. The MB
,
MF
and X
commands of
PLAY
are not useful in a UNIX environment and are
not implemented. The “octave-tracking” feature is also
new.
There are 84 accessible notes numbered 1–84 in 7 octaves numbered 0–6; octave 2 starts with middle C. The tuning is equal-tempered A440.
In the initial state the current octave is 4, the default note duration is quarter notes, the tempo is 120 bpm, and the articulation is non-legato or normal, i.e. half-second notes with the last 1/16th second being “rest time”.
Play strings are interpreted left to right as a series of play command groups. Letter case is ignored. Whitespace between groups is ignored and may be used to separate melody sections. Play command groups are as follows:
C
,
D
, E
,
F
, G
,
A
, B
A
’ through
‘G
’ cause the corresponding note to
be played in the current octave. A note letter may optionally be followed
by an
accidental
sign, one of ‘#
’,
‘+
’, or
‘-
’; the first two of these cause it
to be sharped one half-tone, the last causes it to be flatted one
half-tone. It may also be followed by a time value number and by sustain
dots (see below). Time values are interpreted as for the
‘L
’ command below;.O
n,
OL
, ON
OL
’ enables, and
‘ON
’ disables
octave-tracking
(it is disabled by default). When octave-tracking is on, interpretation of
a pair of letter notes will change octaves if necessary in order to make
the smallest possible jump between notes. Thus
“olbc
” will be played as
“olb>c
”, and
“olcb
” as
“olc<b
”. Octave tracking is
temporarily disabled for one letter note that follows
‘>
’,
‘<
’ or
‘O
n’.>
<
N
nL
nL4
”, quarter notes. The lowest
possible value is 1; values up to 64 are accepted.
“L1
” sets whole notes,
“L2
” sets half notes,
“L4
” sets quarter notes, etc...P
n,
~
nL
’. May be followed by sustain
dots.T
nTempo | BPM | |
very slow | Larghissimo | |
Largo | 40–60 | |
Larghetto | 60–66 | |
Grave | ||
Lento | ||
Adagio | 66–76 | |
slow | Adagietto | |
Andante | 76–108 | |
medium | Andantino | |
Moderato | 108–120 | |
fast | Allegretto | |
Allegro | 120–168 | |
Vivace | ||
Veloce | ||
Presto | 168–208 | |
very fast | Prestissimo |
ML
,
MN
, MS
MN
’ (for normal)
is the default; the last 1/8th of the note's value is rest time. You can
set ‘ML
’ for legato (no rest time)
or ‘MS
’ for staccato (1/4 rest
time).Notes, that is, C
,
D
, E
,
F
, G
,
A
, B
, or
N
command character groups, may be followed by
sustain dots. Each dot causes the note's value to be lengthened by one-half
for each one. Thus, a note dotted once is held for 3/2 of its undotted
value; dotted twice, it is held 9/4, and three times would give 27/8.
This speaker
device was originally for the
pcppi PC timer interface. Support was added for a synthesized device by
Nathanial Sloss, first appearing in NetBSD 8.0.
Eric S. Raymond <esr@snark.thyrsus.com>
Due to roundoff in the pitch tables and slop in the tone-generation and timer hardware (neither of which was designed for precision), neither pitch accuracy nor timings will be mathematically exact.
There is no volume control.
The action of two or more sustain dots does not reflect standard musical notation, in which each dot adds half the value of the previous dot modifier, not half the value of the note as modified. Thus, a note dotted once is held for 3/2 of its undotted value; dotted twice, it is held 7/4, and three times would give 15/8. The multiply-by-3/2 interpretation, however, is specified in the IBM BASIC manual and has been retained for compatibility.
In play strings which are very long (longer than your system's physical I/O blocks) note suffixes or numbers may occasionally be parsed incorrectly due to crossing a block boundary.
June 13, 2017 | NetBSD 10.99 |