world of sound Spectrum - Chapter 4.1: Programming sound effects - Tone, Noise, Complexes effects.

<b>world of sound Spectrum</b> - Chapter 4.1: Programming sound effects - Tone, Noise, Complexes effects.

  4.1. Programming Sound Effects


   In fact, programming effects
code differs little from similar classes in Basic, but you get 
a significant advantage at the expense of speed. Therefore, 
other than pure tones in assembler, you can create and noise. 


                4.1.1. Tone


   We begin with the effects based on the generation of tones. 
What are they? Roughly the same as the effects in Basic:

the sound of smoothly varying frequency. For
complete similarity can even use
the same routine from ROM: 1415.

 10 LD B, 30; B = number of notes
 20 LD HL, 100; HL = start frequency
 30 LOOP LD DE, 2; DE = duration
 1940 PUSH HL; conservation HL
 1950 PUSH BC; preservation BC
 60 CALL 949, call ROM routines
 1970 POP BC; restore BC
 1980 POP HL; recovery HL
 90 LD DE, 25; DE = step frequency changes
100 ADD HL, DE; increase in HL
110 DJNZ LOOP; cycle
120 RET; return to BASIC
2

   Most likely, you've noticed that in this
effect does not prohibit termination, and signal quality no 
worse (see chapter "How is sound"). The fact is

that routine is called to do everything myself.

   If you have already managed to recruit and run
this fragment, it probably felt the difference in the sound, 
not in favor of BASIC. 

   Modify somewhat the effect
possible by changing the frequency is not the whole but only its
Low byte:
1415.
 10 LD B, 60; B = number of notes
 20 LD C, 50; C = step frequency changes
 30 LD HL, 300; HL = start frequency
 40 LOOP LD DE, 10; DE = duration
 1950 PUSH HL; conservation HL
 1960 PUSH BC; preservation BC
 70 CALL 949, call ROM routines
 1980 POP BC; restore BC
 1990 POP HL; recovery HL
100 LD A, L; uveli110 ADD C; chenie
120 LD L, A; L
130 DJNZ LOOP; cycle
140 RET; return to BASIC
2

   The use of sub-ROMs proceed to creating your own. The sound 
of the previous examples can be made smoother and more 
prolonged: 1415.

 10 DI; ban interrupt
 20 XOR A; A = border color (0)
 30 LD B, 255; B = initial frequency
 40 LD C, 255; C = duration
 50 BEEP XOR 16; inverting bits D4
 60 OUT (254), A; output to port A 254
 1970 PUSH BC; preservation BC
 1980 LOOP DJNZ LOOP; delay
 1990 POP BC; restore BC
100 DEC B; decrease in B
110 DEC C; C = C-1
120 JR NZ, BEEP; if C <> 0 then loop
130 EI; permission to interrupt
140 RET; return to BASIC
2

   The possibilities of this effect can be easily increased to:
1415.
 10 DI; ban interrupt
 20 XOR A; A = border color (0)
 30 LD B, 255; B = number of notes
 40 LD C, 1; C = initial frequency
 50 LOOP1 PUSH BC; preservation BC
 60 LD B, 5; B = length
 70 LOOP2 XOR 16; inverting bits D4
 80 OUT (254), A; output to port A 254
 1990 PUSH BC; preservation BC
100 LD B, C; B = C
110 LOOP3 DJNZ LOOP3; delay
120 POP BC; restore BC
130 DJNZ LOOP2; cycle
140 POP BC; restore BC
150 INC C; increase in C
160 DJNZ LOOP1; second cycle
170 EI; permission to interrupt
180 RET; return to BASIC
2

   Most likely, you've noticed that in the first
variant delay is reduced, and the second
increases. Nothing prevents you to change
direction of change. It only
should choose DEC (decrease) or
INC (increase). You can also configure and
duration, start frequency, etc.

   You can change the pitch of the frequency shift:
1415.
 10 DI; ban interrupt
 20 XOR A; A = border color (0)
 30 LD B, 255; B = initial frequency
 40 LD C, 255; C = duration
 50 BEEP XOR 16; inverting bits D4
 60 OUT (254), A; output to port A 254
 1970 PUSH BC; preservation BC
 1980 LOOP DJNZ LOOP; delay
 1990 POP BC; restore BC
100 EX AF, AF '; shift registers A and F on

                                    Alternative
110 LD A, B; A = B
120 SUB 3; A = A-3
130 LD B, A; B = A
140 EX AF, AF '; feedback shift registers
150 DEC C; C = C-1
160 JR NZ, BEEP; if C <> 0 then loop
170 EI; permission to interrupt
180 RET; return to BASIC
2

   Now we use the freedom of action,
which we provide programming
in the codes. We write the non-standard procedure
Runtime:
1415.
 10 DI; ban interrupt
 20 LD D, 10; D = delay 1
 30 LD E, 100; E = Delay 2
 40 LD C, 255; C = duration
 50 XOR A; A = border color (0)
 60 LOOP1 XOR 16; inverting bits D4
 70 OUT (254), A; output to port A 254
 80 LD B, D; B = D
 90 LOOP2 DJNZ LOOP2; delay
100 XOR 16; inverting bits D4
110 OUT (254), A; output to port A 254
120 LD B, E; B = E
130 LOOP3 DJNZ LOOP3; delay
140 INC D; increase in D
150 INC E; increase in E
160 DEC C; C = C-1
170 JR NZ, LOOP1; if C <> 0 then loop
180 EI; permission to interrupt
190 RET; return to BASIC
2

   Here, too, can be long and carefully
vary the parameters (see Appendix 1 -
Flowing 2).

   Quite an interesting effect is obtained by using the 
register R, value under seven bits of which increases

after the next machine cycle. This effect can be described as 
"polushumom. 

   Here is an example of such an effect:
1415.
 10 DI; ban interrupt
 20 LD C, 53; C = delay 1
 30 LD B, 207; B = Delay 2
 40 LD E, 203; E = duration
 50 LD D, 0; D = Border color
 60 LD A, 128; A = temp (0 / 128)
 70 LD R, A; R = A
 80 BEGIN LD A, R; A = R
 90 PAUS1 DEC A; A = A-1
100 JR NZ, PAUS1; if A <> 0 then loop
110 LD A, D; A = D
120 OR 16; setting bit D4
130 OUT (254), A; output to port A 254
140 LD A, C; A = C
150 PAUS2 DEC A; A = A-1
160 JR NZ, PAUS2; if A <> 0 then loop
170 LD A, D; A = D
180 OUT (254), A; output to port A 254
190 LD A, B; A = B
200 PAUS3 DEC A; A = A-1
210 JR NZ, PAUS3; if A <> 0 then loop
220 INC C; C = C +1
230 INC B; B = B +1
240 DEC E; E = E-1
250 JR NZ, BEGIN; if E <> 0 then loop
260 EI; permission to interrupt
270 RET; Returns
2

   Values in lines 20 and 30 define
delay between the differences of level, in line
40 - duration of effect, in line 50 -
Border color, and line 60 - the tempo. In
line 60 makes sense to use only
values 0 and 128, since all other
will be similar to this. In lines 220 and 230
You can set the law of variation of both
delay (command INC, DEC and NOP with the registers B and C in 
any combination). 

   If you do not get caught in all these examples, then move on 
to the generation of noise. If are you still did not 
understand, I advise you to test these effects and their 
poizmenyat parameters.



                4.1.2. Noise


   What is the fuss? This sequence of pulses of random 
duration. Therefore, in order to create us need random data. 
Where their get it? The only suitable source -

ROM, which contains the BASIC interpreter. ROM located at 
address 0 to 16383 (# 3FFF). It is true that these values 
will not completely random, or rather not random, but they 
gave us. 

   Create noise in two different ways. They differ slightly in 
sound. The first consists in the withdrawal of the port values 
read from the ROM. The second - to use these values as

delay.

   In the generation of noise in any of these methods do not 
necessarily prohibit the interruption, as a crackling noise 
heard will not. 

   When you use the first method of
each byte can retrieve data on eight passes cycle of 
reproduction, but it is not beneficial to the software point of 
view. Therefore, most of the effects of bytes

takes one value. For example:
1415.
 10 LD HL, 0; HL = address of ROM
 20 LD BC, 1000; BC = length
 30 BEGIN PUSH BC; preservation BC
 40 LD A, (HL); A = cell contents ROM
 50 AND 240; reset bits curb
 60 OUT (254), A; output to port A 254
 70 LD B, 50; B = frequency
 1980 LOOP DJNZ LOOP; delay
 90 INC HL; HL = HL +1
100 POP BC; restore BC
110 DEC BC; BC = BC-1
120 LD A, B; BC =
130 OR C; 0?
140 JR NZ, BEGIN; cycle
150 RET; return to BASIC
2

   An example of the second method:
1415.
 10 LD HL, 0; HL = address of ROM
 20 LD BC, 1000; BC = length
 30 XOR A; A = border color (0)
 40 BEGIN PUSH BC; preservation BC
 50 XOR 16; inverting bits D4
 60 OUT (254), A; output to port A 254
 70 LD B, (HL); B = cell contents ROM
 80 LOOP1 DJNZ LOOP1; delay
 90 LD B, 40; B = frequency
100 LOOP2 DJNZ LOOP2; delay
110 INC HL; HL = HL +1
120 POP BC; restore BC
130 DEC BC; BC = BC-1
140 LD D, A; preservation A
150 LD A, B; BC =
160 OR C; 0?
170 LD A, D; A recovery
180 JR NZ, BEGIN; cycle
190 RET; return to BASIC

2 If these effects team replaced INC HL INC L, then they will 
sound like to galloping. This is due to the fact

that the data are taken not from the entire set
of ROM, as part of its 256
bytes. And, when this part ends
reading continues from the beginning.

   Try poizmenyat other options.

   The next step - the noise with varying frequency. It will 
look like this: 1415.

 10 LD HL, 0; HL = address of ROM
 20 LD B, 100; B = length of effect
 30 LD C, 10; C = initial frequency
 40 LOOP1 PUSH BC; preservation BC
 50 LD B, 20; B = length
 60 LOOP2 LD A, (HL); A = cell contents ROM
 70 AND 240; reset bits curb
 80 OUT (254), A; output to port A 254
 1990 PUSH BC; preservation BC
100 LD B, C; B = C
110 LOOP3 DJNZ LOOP3; delay
120 INC HL; HL = HL +1
130 POP BC; restore BC

1415.140 DJNZ LOOP2; cycle
150 POP BC; restore BC
160 INC C; increase delay
170 DJNZ LOOP1; cycle
180 RET; return to BASIC
2

   This effect can be changed beyond recognition: Change the 
length, frequency, duration, pitch shift in the frequency, 
direction, frequency offset (command INC C or DEC C), type of 
noise (or command INC HL INC L).


   Another version of Sound Effect:
1415.
 10 LD HL, 0; HL = address of ROM
 20 LD D, 100; D = delay 1
 30 LD E, 10; E = Delay 2
 40 LD C, 255; C = duration
 50 XOR A; A = border color (0)
 60 BEGIN XOR 16; inverting bits D4
 70 OUT (254), A; output to port A 254
 80 LD B, (HL); B = cell contents ROM
 90 LOOP1 DJNZ LOOP1; delay 1
100 LD B, D; B = D
110 LOOP2 DJNZ LOOP2; Delay 2
120 XOR 16; inverting bits D4
130 OUT (254), A; output to port A 254
140 LD B, (HL); B = cell contents ROM
150 LOOP3 DJNZ LOOP3; delay 3
160 LD B, E; B = E
170 LOOP4 DJNZ LOOP4; delay 4
180 INC HL; HL = HL +1
190 INC D; increase in D
200 INC E; increase in E
210 DEC C; C = C-1
220 JR NZ, BEGIN; if C <> 0 then loop
230 RET; return to BASIC
2

   On this example can be fun because
as long as over all the previous ones.

   All the effects presented in this chapter can be regarded as 
a blank. To get the final version, you

may have to work hard. As already
it was said, they all have a huge number of options. In 
addition, you can combine multiple effects together, or cause 
them to run in a loop, etc. All the basic principles of 
combination effects are listed in chapter 2.1. 

   All effects were written so that you can
could change the maximum number of parameters. In cases of a 
particular application they can be greatly simplified. Here's 
an example combined and simplified the effect:

1415.
 10 DI; ban interrupt
 20 LD E, 100; E = cycle time
 30 LD C, 0; C = color of the border
 40 LD B, 4; B = number of cycles
 50 LD L, 1; L = frequency offset
 60 LD H, 30; H = initial frequency
 70 LOOP1 LD D, E; D = E
 80 LOOP2 LD A, C; A = C
 90 XOR 16; inverting bits D4
100 OUT (254), A; output to port A 254
110 LD C, A; C = A
120 LD A, H; A = H
130 ADD A, L; add L to the A
140 LD H, A; H = A
150 LOOP3 DEC A; A = A-1
160 JR NZ, LOOP3; if A <> 0 then loop
170 DEC D; D = D-1
180 JR NZ, LOOP2; if D <> 0 then loop
190 LD A, L; A = L
200 NEG; the sign of the register A
210 LD L, A; L = A
220 DJNZ LOOP1; cycle
230 EI; permission to interrupt
240 RET; Returns
2

   All of the above effects can
customize your own needs. For example,
change the color of the border or make it so
except that the signal dynamics when the SIM
tape recorder (for this team all XOR 16
must be replaced by XOR 24 and AND 240 AND
248).


         4.1.3. Complexes effects


   Usually in games (and in any other
programs) is not used one or two
sound effects, and much more. Therefore, the effects 
conveniently grouped (Complexes) and call them on the

a subroutine, passing it as parameter number effect.

   If the effects are varied and play various sub-programs, the 
table of effects is best stored addresses these routines. In 
this case, to reproduce the effects you can use this 
subroutine: 1415.

 10 ADD A, A; A = A * 2
 20 LD E, A; DE
 30 LD D, 0; = A
 40 LD HL, TABLE; HL = address of table
 50 ADD HL, DE; HL = HL + DE
 60 LD E, (HL); DE =
 70 INC HL; address
 80 LD D, (HL); routines
 90 EX DE, HL; exchange values HL and DE
100 JP (HL); subroutine call effect
110 TABLE DEFW ... , Address table
2

   Before calling this subroutine in the register A has to 
enter number effect. Do not forget to fill in the table 
addresses effects. Naturally, the effects themselves must be 
located at the address. No in no case should indicate the 
number of effect greater than the number listed in the table 
routines, otherwise the computer will freeze or "reset". Note 
also that this subprogram can work a maximum of

127 effects.

   If the effects are similar and reproduce the same routine, 
then Table of effects parameters can be stored

This subroutine. Here's an example that uses this method:
1415.
 10 LD E, A; A
 20 ADD A, A; =
 30 ADD A, E; A * 3
 40 LD E, A; DE
 50 LD D, 0; = A
 60 LD HL, TABLE; HL = address of table
 70 ADD HL, DE; HL = HL + DE
 80 LD C, (HL); C = duration
 90 INC HL; HL = HL +1
100 LD E, (HL); E = rate
110 INC HL; HL = HL +1
120 LD A, (HL); A = change in frequency
130 LD (CHNG), A; setting frequency
140 DI; ban interrupt
150 XOR A; A = color of the border (0)
160 BEGIN XOR 16; inverting bits D4
170 OUT (254), A; output to port A 254
180 LD B, E; B = E
190 PAUSE DJNZ PAUSE; delay
200 CHNG NOP; reserve for frequency
210 DEC C; C = C-1
220 JR NZ, BEGIN; if C <> 0 then loop
230 EI; permission to interrupt
240 RET; Returns
250 TABLE DEFB 0,0,28; table
260 DEFB 0,0,29;
270 DEFB 0,128,28; effects
280 DEFB 0,128,29;
2

   Before calling this subroutine in the register A has to 
enter number effect. In the above program has already created 
four effects, but you can change them or increase their number. 
When you call the effect, the number which is greater than the 
number described routines can also happen that some awful.


   In this example, the description of the effect given to 
three bytes. The first byte - the duration of effect, the 
second - the initial frequency, and the third - a way to change 
the frequency. Third byte can be 0, 28 and 29. What does it 
mean, respectively, maintaining, increasing and decreasing 
frequency. Enter any other value in this byte is not worth it, 
because it may cause to unpredictable consequences.


   The above program is only
example. You can configure it to work with absolutely any 
effect. 

   This routine can handle a maximum of 85 effects.

   In both of the above routines effects numbering starts with 
zero.