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NAME
speaker, spkr — console speaker device driver
SYNOPSIS
device speaker
#include <dev/speaker/speaker.h>
DESCRIPTION
The speaker device driver allows applications to control the PC console speaker on an
IBM-PC--compatible machine running FreeBSD.
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 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(2) request for tone generation
at arbitrary frequencies is also supported.
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.
Applications may call ioctl(2) on a speaker file descriptor to control the speaker driver
directly; definitions for the ioctl(2) interface are in <dev/speaker/speaker.h>. The tone_t
structure used in these calls has two fields, specifying a frequency (in Hz) and a duration
(in 1/100ths of a second). A frequency of zero is interpreted as a rest.
At present there are two such ioctl(2) calls. SPKRTONE accepts a pointer to a single tone
structure as third argument and plays it. SPKRTUNE accepts a pointer to the first of an
array of tone structures and plays them in continuous sequence; this array must be
terminated by a final member with a zero duration.
The play-string language is modeled on the PLAY statement conventions of IBM Advanced BASIC
2.0. The MB, MF, and X primitives of PLAY are not useful in a timesharing environment and
are omitted. The `octave-tracking' feature and the slur mark are new.
There are 84 accessible notes numbered 1-84 in 7 octaves, each running from C to B, numbered
0-6; the scale is equal-tempered A440 and octave 3 starts with middle C. By default, the
play function emits 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. Play command groups are as follows:
CDEFGAB Letters 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 If n is numeric, this sets the current octave. n may also be one of L or N to
enable or disable 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 locking
is disabled for one letter note following >, < and O[0123456]. (The octave-
locking feature is not supported in IBM BASIC.)
> Bump the current octave up one.
< Drop the current octave down one.
N n Play note n, n being 1 to 84 or 0 for a rest of current time value. May be
followed by sustain dots.
L n Sets the current time value for notes. The default is L4, quarter or crotchet
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 Pause (rest), with n interpreted as for L n. May be followed by sustain dots.
May also be written ~.
T n Sets the number of quarter notes per minute; default is 120. Musical names for
common tempi are:
Tempo Beats Per Minute
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
M[LNS] Set articulation. MN (N 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 space) or MS for staccato
(1/4 rest space).
Notes (that is, CDEFGAB 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.
A note and its sustain dots may also be followed by a slur mark (underscore). This causes
the normal micro-rest after the note to be filled in, slurring it to the next one. (The
slur feature is not supported in IBM BASIC.)
Whitespace in play strings is simply skipped and may be used to separate melody sections.
FILES
/dev/speaker speaker device file
SEE ALSO
spkrtest(8)
HISTORY
The speaker device appeared in FreeBSD 1.0.
AUTHORS
Eric S. Raymond <esr@snark.thyrsus.com>, June 1990
PORTED BY
Andrew A. Chernov <ache@astral.msk.su>
BUGS
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.