118 lines
5.1 KiB
Groff
118 lines
5.1 KiB
Groff
.TH SPKR 4
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.SH NAME
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spkr \- console speaker device driver
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.SH DESCRIPTION
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The speaker device driver allows applications to control the PC console
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speaker on an IBM-PC-compatible machine running UNIX.
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.PP
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Only one process may have this device open at any given time; open() and
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close() are used to lock and relinquish it. An attempt to open() when
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another process has the device locked will return -1 with an EBUSY error
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indication. Writes to the device are interpreted as 'play strings' in a
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simple ASCII melody notation. An ioctl() for tone generation at arbitrary
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frequencies is also supported.
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.PP
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Sound-generation does \fInot\fR monopolize the processor; in fact, the driver
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spends most of its time sleeping while the PC hardware is emitting
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tones. Other processes may emit beeps while the driver is running.
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.PP
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Applications may call ioctl() on a speaker file descriptor to control the
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speaker driver directly; definitions for the ioctl() interface are in
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sys/spkr.h. The tone_t structure used in these calls has two fields,
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specifying a frequency (in hz) and a duration (in 1/100ths of a second).
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A frequency of zero is interpreted as a rest.
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.PP
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At present there are two such ioctls. SPKRTONE accepts a pointer to a
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single tone structure as third argument and plays it. SPKRTUNE accepts a
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pointer to the first of an array of tone structures and plays them in
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continuous sequence; this array must be terminated by a final member with
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a zero duration.
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.PP
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The play-string language is modelled on the PLAY statement conventions of
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IBM BASIC 2.0. The MB, MF and X primitives of PLAY are not useful in a UNIX
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environment and are omitted. The `octave-tracking' feature is also new.
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.PP
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There are 84 accessible notes numbered 1-83 in 7 octaves, each running from
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C to B, numbered 0-6; the scale is equal-tempered A440 and octave 3 starts
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with middle C. By default, the play function emits half-second notes with the
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last 1/16th second being `rest time'.
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.PP
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Play strings are interpreted left to right as a series of play command groups;
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letter case is ignored. Play command groups are as follows:
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.PP
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CDEFGAB -- letters A through G cause the corresponding note to be played in the
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current octave. A note letter may optionally be followed by an \fIaccidental
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sign\fR, one of # + or -; the first two of these cause it to be sharped one
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half-tone, the last causes it to be flatted one half-tone. It may also be
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followed by a time value number and by sustain dots (see below). Time values
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are interpreted as for the L command below;.
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.PP
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O <n> -- if <n> is numeric, this sets the current octave. <n> may also be one
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of 'L' or 'N' to enable or disable octave-tracking (it is disabled by default).
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When octave-tracking is on, interpretation of a pair of letter notes will
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change octaves if necessary in order to make the smallest possible jump between
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notes. Thus "olbc" will be played as "olb>c", and "olcb" as "olc<b". Octave
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locking is disabled for one letter note following by >, < and O[0123456].
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.PP
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> -- bump the current octave up one.
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.PP
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< -- drop the current octave down one.
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.PP
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N <n> -- play note n, n being 1 to 84 or 0 for a rest of current time value.
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May be followedv by sustain dots.
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.PP
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L <n> -- sets the current time value for notes. The default is L4, quarter
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notes. The lowest possible value is 1; values up to 64 are accepted. L1 sets
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whole notes, L2 sets half notes, L4 sets quarter notes, etc..
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.PP
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P <n> -- pause (rest), with <n> interpreted as for L. May be followed by
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sustain dots. May also be written '~'.
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.PP
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T <n> -- Sets the number of quarter notes per minute; default is 120. Musical
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names for common tempi are:
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.TS
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a a a.
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Tempo Beats Per Minute
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very slow Larghissimo
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Largo 40-60
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Larghetto 60-66
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Grave
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Lento
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Adagio 66-76
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slow Adagietto
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Andante 76-108
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medium Andantino
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Moderato 108-120
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fast Allegretto
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Allegro 120-168
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Vivace
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Veloce
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Presto 168-208
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very fast Prestissimo
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.TE
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.PP
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M[LNS] -- set articulation. MN (N for normal) is the default; the last 1/8th of
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the note's value is rest time. You can set ML for legato (no rest space) or
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MS (staccato) 1/4 rest space.
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.PP
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Notes (that is, CDEFGAB or N command character groups) may be followed by
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sustain dots. Each dot causes the note's value to be lengthened by one-half
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for each one. Thus, a note dotted once is held for 3/2 of its undotted value;
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dotted twice, it is held 9/4, and three times would give 27/8.
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.PP
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Whitespace in play strings is simply skipped and may be used to separate
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melody sections.
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.SH BUGS
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Due to roundoff in the pitch tables and slop in the tone-generation and timer
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hardware (neither of which was designed for precision), neither pitch accuracy
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nor timings will be mathematically exact. There is no volume control.
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.PP
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In play strings which are very long (longer than your system's physical I/O
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blocks) note suffixes or numbers may occasionally be parsed incorrectly due
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to crossing a block boundary.
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.SH FILES
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/dev/speaker -- speaker device file
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.SH AUTHOR
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Eric S. Raymond (esr@snark.thyrsus.com) Feb 1990
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