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Sefx
C Language Sound Effects Library
Version 1.0
20 Feb 92
Copyright (c) 1992 Bri Productions
1
Table of Contents
Introduction
Acknowledgments.........................4
General Description.....................4
Disclaimer..............................4
Registration............................4
Contacting the Author...................5
Terminology.............................5
A typedef...............................5
Control Functions
Description.............................6
SndOpen.................................7
SndClose................................8
SndLen..................................9
SndTbase...............................10
SndFlush...............................11
SndHold................................12
SndTerm................................13
Sound Generation Functions
Description............................14
SndTone................................15
SndPause...............................16
SndString..............................17
SndTrill...............................18
SndSlide...............................19
SndPulse...............................20
2
Miscellaneous
SndMs..................................21
Appendix A - Things to look out for............22
Appendix B - Musical notes.....................23
Appendix C - Sound queue usage.................24
Appendix D - Registration form.................25
3
Acknowledgments.
I would like to thank Earl Jensen for technical review and
advice, James Garcia for musical information and Margaret
Carlsen for proof reading this documentation.
General Description.
Sefx is a C language timer-driven sound effects library for IBM
and compatible computers. Sefx is compatible with most if not
all DOS based C compilers.
All the sound generated by Sefx is generated in the background.
This fact allows the program to continue with other operations
while the sound is generated.
Some of Sefx's features are:
∙ Generates sound simultaneously to other operations
∙ Produces frequencies from 19 to 20,000+ hertz
∙ Time bases of 54.9, 27.5, 13.7 and 6.9 milliseconds
∙ Changes frequency up to 145 time per second
∙ Adjustable sound queue as large as 65532 bytes
∙ Sound queue is handled internally
∙ Written in assembly language for optimum speed and efficiency.
DISCLAIMER.
Sefx is provided AS IS. Bri Productions specifically disclaims
any and all warranties, expressed or implied, including fitness
for a particular purpose. Use this product at your own risk.
Registration.
Sefx is a user supported software product. Distribution of
this product, unaltered and without charge, is encouraged. If
you find this product useful, you are encouraged to register
your copy. This allows Bri Productions to continue to provide
support low cost, high quality shareware.
The registration fee is $20.00 US dollars and includes libraries
for small, medium, compact and large memory models and complete
source code. A registration form is provided in Appendix D.
4
Contacting the author.
Bri Productions may be contacted by any of the following means:
CompuServe - 76635,2246
U.S. mail - Bri Productions
P.O.Box 7121
Fremont, CA 94537-7121
CompuServe is a trademark of CompuServe Inc.
Terminology
This section is intended to define the terminology used in this
documentation and clarify any ambiguities thereof.
A 'tone' consists of a single frequency and a 'duration'. A
'pause' is the same in all respects as a 'tone' except for the
absents of a frequency. It can also be defined as a 'tone' with
a frequency of zero.
A 'sound' is one or more 'tones' and/or 'pauses' put together
to produce the desired results. ie. trill, slide, string, etc.
A 'sound' may consist of only one 'tone' or 'pause'. Each Sefx
sound generation function generates exactly one sound.
The 'time base' refers to the length of time of one 'tic' which
is the basic unit of time used by the Sefx sound generating
functions. A new 'tone' or 'pause' may be loaded as often as
once per 'tic'. Hence the frequency may be changed as often
as the value of the 'time base'.
The 'duration' of a 'tone' is the number of 'tics' (and hence
the length of time) it will last.
Examples:
A 'tone' with a 'duration' of two 'tics', when the
'time base' is set to MEDium (27.5ms), will last 55
milliseconds.
A 'sound' consisting of a 'tone' with a 'duration' of of
two 'tics', a 'pause' with a 'duration' of one 'tic'
followed by another tone with a 'duration' of three 'tics'
when the 'time base' is set to HIGH (13.7ms), will last
82.2 milliseconds.
A typedef
You will see the data type 'TONE' throughout the Sefx library.
TONE is a structure, defined in sefx.h, used for storing
frequency/duration pairs. This type is used mainly by the
function SndString. The fields are defined as follows:
typedef struct{
int freq; /* frequency */
int durtn; /* duration */
}TONE;
5
Control Functions
Before sound can be generated, a call to SndOpen must be made
to initialize Sefx. SndOpen will also allocate memory for a sound
queue. Sounds are then loaded into the sound queue and played in
sequence
Prior to program's termination, a call to SndClose must be made
to undo SndOpen. Failing to call SndClose prior to a program's
termination will cause the computer to lock up requiring a
reboot.
Other control functions are available for manipulating and
procuring the status of the sound queue. The sound queue can
be flushed at any time with SndFlush. SndTerm terminates the
current sound while SndHold will put all sound on hold. The
number of bytes currently residing in the sound queue is available
through SndLen.
6
----------------------------------------------------------------
SndOpen
----------------------------------------------------------------
Function
Initializes the timer and interrupt handler and allocates
memory for the sound queue.
Syntax
#include "sefx.h"
int SndOpen(unsigned Qsize, int tbase);
Parameters
Qsize - Size of the sound queue in bytes. The number
of bytes required for a sound varies depending
on the sound. This value will be rounded down
so that it is even multiple of 4 bytes.
tbase - Time base. This value determines the length of
time of one tic and subsequently how often the
frequency can be changed. Possibilities are:
LOW (3) - 54.9 milliseconds
MED (2) - 27.5 milliseconds
HIGH (1) - 13.7 milliseconds
ULTRA (0) - 6.9 milliseconds
Remarks
SndOpen initializes the timer chip, installs the
timer interrupt handler, allocates memory for the
sound queue and sets the time base.
The time base determines how long one tic will be. Since
a new tone can be loaded as often as once per tic, this
value also determines how often the frequency can be
changed.
After a call to SndOpen, a subsequent call to SndClose
must be made prior to the program's termination.
Return value
SndOpen returns a zero if no errors occur, or non
zero on an error. Constants are defined in sefx.h
as follows:
NOERR (0) - no errors
OPENED (1) - Sefx already opened
MALLOC_ERR (4) - queue allocation error
7
See also
SndClose SndTbase
Example
Initialize Sefx, allocate a 1023 byte sound queue and
set the time base to MEDium resolution.
#define QSIZE 1024
{
int rv;
rv = SndOpen(QSIZE, MED);
if(rv)
{
... error handler
}
----------------------------------------------------------------
SndClose
----------------------------------------------------------------
Function
Restores the timer and timer interrupt, and releases the
sound queue from memory.
Syntax
#include "sefx.h"
void SndClose(void);
Remarks
SndClose restores the timer interrupt vector and the
timer chip to normal, and releases the memory allocated
for the sound queue.
A call to SndClose is required prior to the program's
termination.
See also
SndOpen
8
Example
Restore the interrupt vector and free the sound queue
prior to termination
{
... closing code
SndClose();
}
----------------------------------------------------------------
SndLen
----------------------------------------------------------------
Function
Determines how many bytes are currently occupying the
sound queue.
Syntax
#include "sefx.h"
unsigned SndLen(void);
Remarks
SndLen determines how many bytes are currently occupying
the sound queue. The value is a direct representation
of how full the sound queue actually is and does not
necessarily represent how much time is left in the queue.
Return value
SndLen returns the number of bytes currently residing in
the sound queue.
See also
SndFlush SndHold SndTerm
9
Example
Check if there is room for 10 more bytes in the sound
queue.
#define THRESH 512
#define SndThresh() (SndLen() < THRESH)
{
if(SndThresh())
{
...load more sound
}
}
----------------------------------------------------------------
SndTbase
----------------------------------------------------------------
Function
Sets the time base.
Syntax
#include "sefx.h"
int SndTbase(int tbase);
Parameters
tbase - Time base. This value determines the length of
time of one tic and subsequently how often the
frequency can be changed. Possibilities are:
LOW (3) - 54.9 milliseconds
MED (2) - 27.5 milliseconds
HIGH (1) - 13.7 milliseconds
ULTRA (0) - 6.9 milliseconds
Remarks
SndRes sets the time base. This value determines the
length of time of one tic, the basic unit of time used
by Sefx. Since a new tone can be loaded as often as once
per tic, the time base determines how often the frequency
can be changed.
Return value
SndTbase returns the previous time base.
10
See also
SndOpen
Example
Set the time base to 6.9 milliseconds per tic, later
restoring the original time base.
{
int org_tb;
org_tb = SndTbase(ULTRA);
... short tones
}
{
... later
SndTbase(org_tb);
}
----------------------------------------------------------------
SndFlush
----------------------------------------------------------------
Function
Flushes all sound.
Syntax
#include "sefx.h"
void SndFlush(void);
Remarks
SndFlush flushes the sound queue, deleting all pending
and current sounds. It also terminates the current tone.
See also
SndLen SndTerm SndHold
11
Example
Play a song after displaying the opening screen until
the user hits a key.
{
...display opening screen
SndString(song, 100, 0);
getch();
SndFlush();
...continue
}
----------------------------------------------------------------
SndHold
----------------------------------------------------------------
Function
Puts all sound on hold or releases from hold.
Syntax
#include "sefx.h"
int SndHold(int on_off);
Parameters
on_off - hold on/off switch. Possibilities are
ON (1) - put on hold
OFF (0) - release from hold
Remarks
SndHold puts all sound on hold or releases it from a
previous hold condition. When a hold is set, the
current tone as well as the sound queue is immediately
frozen until it is subsequently released from hold.
When a hold condition is released, the sounds will
resume where it left off.
Return value
SndHold returns the previous hold condition
12
See also
SndFlush SndTerm
Example
Make sure the sound is on hold temporarily and then
restore it to it's previous condition
{
int prev_hold;
prev_hold = SndHold(ON);
... guaranteed quiet time
SndHold(prev_hold);
}
----------------------------------------------------------------
SndTerm
----------------------------------------------------------------
Function
Terminates the current sound.
Syntax
#include "sefx.h"
void SndTerm(void);
Remarks
SndTerm terminates the current sound. The sound may be a
single tone or many tones. In either case all the tones
that make up the sound are terminated.
See also
SndFlush SndHold
Example
Terminate the alarm when the user responds
#define CONTINUOUS 0
#define Alarm() SndTrill(1400, 600, 8, 8, CONTINUOUS)
{
Alarm();
... wait for response
SndTerm();
}
13
Sound Generation
Sound generation functions load sounds into the sound queue to be
played in sequence. Most of the sound generation functions allow
the sound to be repeated a specified number of times or
continuously.
A sounds consisting of a single tone is loaded with SndTone while
a sound consisting of a string of tones can be loaded with
SndString.
Sefx provides sound generation functions for the more common types
of sounds. This includes trills, pulses and slides created by
the functions SndTrill, SndPulse and SndSlide respectively.
These basic sounds can create a multitude of sounds themselves and
in addition can be used with other sound generation functions to
create more complex combinations.
14
----------------------------------------------------------------
SndTone
----------------------------------------------------------------
Function
Loads a single tone into the sound queue.
Syntax
#include "sefx.h"
void SndTone(int freq, int durtn);
Parameters
freq - frequency of the tone in hertz.
durtn - number of tic the tone will last.
Remarks
SndTone loads single tone of the specified frequency and
duration into the sound queue. Specifying a duration of 0
causes the tone to be played continuously. Specifying a
frequency of 0 will generate a pause. The single tone is
considered to be one sound.
See also
SndString SndPause SndTbase SndMs
Example
Make a two second beep at 2000 hertz.
{
int second;
... made an error
second = SndMs(1000);
SndTone(2000, 2*second);
}
15
----------------------------------------------------------------
SndPause
----------------------------------------------------------------
Function
Loads a pause into the sound queue.
Syntax
#include "sefx.h"
void SndPause(int durtn);
Parameters
durtn - number of tics the tone will last
Remarks
SndPause loads a pause (no sound) of the specified
duration into the sound queue. The pause is considered to
be one sound.
SndPause is a function macro defined as SndTone(0, durtn).
See also
SndTone SndTbase SndMs
Example
Insert a three beat pause between two notes
#define A 440
#define B 494
{
int beat;
beat = SndMs(500);
SndTone(A, 3*beat);
SndPause(3*beat);
SndTone(B, 3*beat);
}
16
----------------------------------------------------------------
SndString
----------------------------------------------------------------
Function
Loads a string of tones into the sound queue.
Syntax
#include "sefx.h"
void SndString(const TONE *str, int count, unsigned reps);
Parameters
str - pointer to an array of type TONE were the
string of tones are stored.
count - number of tones in the array.
reps - number of times to repeat the string of
tones.
Remarks
SndString loads an string of tones, stored in an array
of type TONE, into the sound queue. The string of tone
will be repeated as specified. Specifying a repetition of
0 will cause the string to be repeated continuously.
The string of tones is considered to be one sound.
See also
SndTone SndTbase SndMs SndPause
Example
Play the scale of notes one time.
#define C 262
#define D 294
#define E 330
#define F 349
#define G 392
#define A 440
#define B 494
{
TONE scale[7] = { {C,3},{D,3},{E,3},{F,3},
{G,3},{A,3},{B,3}
};
SndString(scale, 7, 1);
}
17
----------------------------------------------------------------
SndTrill
----------------------------------------------------------------
Function
Loads a trill sound into the sound queue.
Syntax
#include "sefx.h"
void SndTrill(int freq1, int freq2,
int durtn1, int durtn2, int reps);
Parameters
freq1 - frequency of the first tone in hertz.
freq2 - frequency of the second tone in hertz.
durtn1 - number of tics the first tone will last.
durtn2 - number of tics the second tone will last.
reps - number of times to repeat the trill sound.
Remarks
SndTrill loads a trill sound into the sound queue. The
trill is repeated as specified. Specifying a repetition
of 0 will cause the trill to be repeated continuously.
A trill sound is sometimes referred to as a flip-flop sound.
See also
SndSlide SndPulse SndMs SndTbase
Example
Make a telephone ring five times.
{
int i = 5;
while(i--)
{
SndTrill(1400, 600, 1, 1, 10);
SndPause(22);
}
}
18
----------------------------------------------------------------
SndSlide
----------------------------------------------------------------
Function
Loads sliding tones into the sound queue.
Syntax
#include "sefx.h"
void SndSlide(int start, signed dfreq,
int durtn, int reps);
Parameters
start - frequency of the starting tone in hertz.
dfreq - change (delta) in frequency per tic.
durtn - number of tic the slide will last.
reps - number of times to repeat the slide.
Remarks
SndSlide loads sliding tones into the sound queue. The
frequency is increased (positive 'dfreq') or decreased
(negative 'dfreq') on each tic by the specified delta
frequency. The sliding tone will last the specified
duration and will be repeated as specified.
To calculate the frequency of the ending tone in the slide
use: end = start + (durtn - 1) * dfreq.
Hint: shorter (faster) time bases generate a smoother
sounding slide while longer (slower) time bases generate
a more course sounding slide. Both cases can be useful
for creating the desired effect.
See also
SndTrill SndPulse SndMs SndTbase
Example
Play a sliding tone from 2000 hertz to 992 hertz
{
SndSlide(2000, -28, 37);
}
19
----------------------------------------------------------------
SndPulse
----------------------------------------------------------------
Function
Loads a pulsing sound into the sound queue.
Syntax
#include "sefx.h"
void SndPulse(int freq, int durtn,
int pdurtn, int reps);
Parameters
freq - frequency of the tone in hertz.
durtn - number of tics the tone will last.
pdurtn - number of tics the pause will last.
reps - number of times to repeat the pulse.
Remarks
SndPulse loads a tone of the specified frequency and
duration, followed by a pause of the specified duration
The sound is repeated as specified. Specifying a repetition
of 0 will cause the pulse to repeat continuously.
SndPulse is a function macro defined as:
SndTrill(freq, 0, durtn, pdurtn, reps);
See also
SndTrill SndSlide SndMs SndTbase
Example
Make a wrist watch alarm. (Time base = LOW/54.9)
{
int i = 3;
while(i--)
{
SndPulse(4250, 2, 1, 3);
SndPause(9);
}
}
20
----------------------------------------------------------------
SndMs
----------------------------------------------------------------
Function
Converts milliseconds to tics.
Syntax
#include "sefx.h"
int SndMs(unsigned ms);
Parameters
ms - number of milliseconds to convert to tics
Remarks
SndMs converts a value in milliseconds to the equivalent
number of tics, rounding off to the nearest tic. SndMs
takes into account the current time base and adjusts
the resulting number of tics accordingly. The number of
tics will always be at least one unless 0 milliseconds is
specified.
Shorter (faster) time bases result in a more precise
conversion than longer (slower) time bases. In most
applications this is an insignificant limitation. In
any case the value will never be off more that the length
of time of one tic.
Return value
SndMs returns the number of tics that is approximately
equal to the specified number of milliseconds.
See also
SndTbase
Example
Make a one second tone at 100 hertz
{
int second;
second = SndMs(1000);
SndTone(100, second);
}
21
Appendix A
Things to look out for.
∙ Sefx takes over interrupt 8 and may change the system clock
rate. If the clock rate is changed, Sefx arbitrates the
timer chain in order that it's rate remains the same. If
a program written with Sefx needs to chain into interrupt 8
it should do so prior to the calling SndOpen.
∙ The functions SndOpen and SndClose make calls to the C
functions malloc and free respectively.
∙ In the small and medium memory models, the near heap where
the sound queue is allocated, is limited. The data segment
(globals etc.) + the stack + allocated memory (sound queue)
must not exceed 64K bytes. If an extremely large sound queue
is required the compact or large model, where the sound queue
can be as large as 65532 bytes, should be used.
22
Appendix B
Musical notes.
This appendix provides information about frequencies of musical
notes and octave shifting.
The Equal Tempered Chromatic Scale (rounded to integer)
note|freq | note|freq | note|freq | note|freq
-------------|-------------|-------------|-------------
C0 16 | C2 65 | C4 262 | C6 1047
C#0 17 | C#2 69 | C#4 277 | C#6 1109
D0 18 | D2 73 | D4 294 | D6 1175
D#0 19 | D#2 78 | D#4 311 | D#6 1245
E0 21 | E2 82 | E4 330 | E6 1319
F0 22 | F2 87 | F4 349 | F6 1397
F#0 23 | F#2 93 | F#4 370 | F#6 1480
G0 25 | G2 98 | G4 392 | G6 1568
G#0 26 | G#2 104 | G#4 415 | G#6 1661
A0 28 | A2 110 | A4 440 | A6 1760
A#0 29 | A#2 117 | A#4 466 | A#6 1865
B0 31 | B2 123 | B4 494 | B6 1976
| | |
C1 33 | C3 131 | C5 523 | C7 2093
C#1 35 | C#3 139 | C#5 554 | C#7 2217
D1 37 | D3 147 | D5 587 | D7 2349
D#1 39 | D#3 156 | D#5 622 | D#7 2489
E1 41 | E3 165 | E5 659 | E7 2637
F1 44 | F3 175 | F5 698 | F7 2794
F#1 46 | F#3 185 | F#5 740 | F#7 2960
G1 49 | G3 196 | G5 784 | G7 3136
G#1 52 | G#3 208 | G#5 831 | G#7 3322
A1 55 | A3 220 | A5 880 | A7 3520
A#1 58 | A#3 233 | A#5 932 | A#7 3729
B1 62 | B3 247 | B5 988 | B7 3951
| C8 4186
Since the frequencies of the octaves increase as a factor of
two, musical notes of the other octaves are easily accomplished
by multiplying or dividing by factors of two, or more
efficiently by shifting left or right. For example to obtain
the frequency of A5, the value of A4 (440) is shifted left
once (multiplied by two). To obtain the frequency of A2,
shift A4 right twice (divide by four).
Examples: A5 = A4 << 1
A2 = A4 >> 2
Note: It is better to shift from a higher octave to a lower
octave since the percent of rounding error, when rounding to an
integer, is smaller with the larger values.
Appendix C
23
Appendix C
Sound queue usage
Some of the sound generation functions load instructional
information as well as frequency and duration information. This
added information allows Sefx to conserve memory. When the sound
is initially loaded by the sound generation function, it will
occupy an 'initial' number of bytes in the sound queue. When the
next sound is fetched from the sound queue, the instructional
information is evaluated and then discarded. The remaining bytes
will continue to occupy the sound queue until the sound is
terminated. This is referred to in the table below as 'residual'.
Initial Residual
--------- ----------
SndTone 4 4
SndPause 4 4
SndString 8 + 4 * len 4 * len
SndTrill 16 8
SndSlide 8 + 4 * durtn 4 * durtn
SndPulse 16 8
24
Appendix D
Sefx v1.0 Registration Form
Name: ______________________________________________________
Company: ___________________________________________________
Address: ___________________________________________________
City: ____________________________ State: _________________
Zip code: _________________ Phone # : _____________________
CompuServe # : _____________________________________________
How did you acquire Sefx ? _________________________________
____________________________________________________________
What functions do you find most useful ?____________________
____________________________________________________________
What functions do you find least useful ?___________________
____________________________________________________________
What functions, not in Sefx, would you like to see ?________
____________________________________________________________
What other types of libraries would you find useful ?_______
__ Serial Communications __ Expanded Memory __ IEEE/GPIB
__ Game Port Others: ______________________________________
registration $ 20.00
California residents add sales tax ( 8.25% ) $________
shipping inside continental U.S. ( $ 2.00 )
shipping outside continental U.S. ( $ 5.00 ) $________
Total: $________
All Payments Must be in U.S. Dollars
Make check or money order payable to: Bri Productions
P.O. Box 7121
Fremont, CA 94537-7121
25
