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Improve explosion sound.

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bellwood420
2021-01-11 19:55:04 +09:00
parent 15512eb28a
commit dfff6d9fcd
1 changed files with 103 additions and 19 deletions
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122
rtl/computer_space_sound.vhd
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@@ -48,6 +48,11 @@
-- [sum over k_fc 0 to 11]
--
--
-- * Explosion
--
-- Randomly frequency-modulated square wave centered at about 100 Hz
-- with intermittent noise.
--
---------------------------------------------------------------------------------
library ieee;
@@ -103,9 +108,9 @@ architecture struct of computer_space_sound is
type t_pond is array(nb_filters) of integer range 0 to 16;
type t_pond_bank is array(nb_voices) of t_pond;
constant pond : t_pond_bank := (
( 0, 16, 16, 16, 8, 8, 4, 4, 2, 2, 1, 0), -- voice 1 - rocket thrust
(16, 8, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0), -- voice 2 - back ambiance
( 4, 16, 2, 2, 1, 1, 0, 0, 0, 0, 0, 1));-- voice 3 - explosion
( 0, 16, 16, 16, 8, 8, 4, 4, 2, 2, 1, 0 ), -- voice 1 - rocket thrust
(16, 8, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0 ), -- voice 2 - back ambiance
( 0, 0, 0, 2, 4, 8, 8, 16, 16, 16, 16, 16));-- voice 3 - explosion background noise
signal add_v : integer range -128*64*16 to 128*64*16-1;
type t_voices is array(nb_voices) of integer range -128*64*16 to 128*64*16-1;
@@ -118,6 +123,25 @@ architecture struct of computer_space_sound is
signal saucer_missile : integer range -32768 to 32767;
signal rocket_missile : integer range -32768 to 32767;
subtype nb_rndmap is integer range 0 to 15;
type t_period_map is array(nb_rndmap) of integer range 0 to 127;
constant period_map : t_period_map := (1,2,3,4,5,6,8,12,18,22,24,25,26,27,28,29);
type t_delta_map is array(nb_rndmap) of integer range 0 to 8191;
constant delta_map : t_delta_map := (500,1000,1500,2000,2500,3000,4000,4000,4500,5000,5500,6000,6500,7000,7500,8000);
constant amplitude : integer range -32768 to 32767 := 25000;
signal rndvalue : nb_rndmap;
signal square_wave : integer range -32768 to 32767;
signal noise_gate : boolean;
signal noisy_square_wave_base : integer range -65536 to 65535;
signal noisy_square_wave : integer range -32768 to 32767;
signal explosion_base : integer range -32768 to 32767;
signal explosion_cmd_r : std_logic;
begin
@@ -226,20 +250,78 @@ begin
end if;
end if;
end process;
end process;
-- explosion wave generation
square_wave_gen : process(clock_50)
variable rise : boolean := false;
variable delta : integer range 0 to 8191 := 0;
variable period_cnt : integer range 0 to 127 := 0;
begin
if reset = '1' then
square_wave <= 0;
rise := false;
delta := 0;
period_cnt := 0;
else
if rising_edge(clock_50) then
if noise_cnt = 0 then -- it's time to make new sample
if rise and (square_wave < amplitude) then -- rising edge
if square_wave + delta > amplitude then
square_wave <= amplitude; -- upper limit
else
square_wave <= square_wave + delta; -- inc value
end if;
elsif not(rise) and (square_wave > -amplitude) then -- falling edge
if square_wave - delta < -amplitude then
square_wave <= -amplitude; -- lower limit
else
square_wave <= square_wave - delta; -- dec value
end if;
end if;
if period_cnt = 70 then -- reached the end of half-cycle
period_cnt := period_map(rndvalue); -- random start count for modulating frequency
delta := delta_map(rndvalue); -- random delta value fot obtaining waveform irregularity
rise := not(rise); -- alternate rise and fall
noise_gate <= rndvalue < 6; -- random gate for intermittent noise
else
period_cnt := period_cnt + 1;
end if;
end if;
end if;
end if;
end process;
rndvalue <= to_integer(unsigned(noise_reg(3 downto 0))); -- 4-bit random value
noisy_square_wave_base <= square_wave + voices(1) when noise_gate else square_wave; -- add intermittent noise
process(noisy_square_wave_base) -- clip noise exceeding amplitude
begin
if (noisy_square_wave_base > amplitude) then
noisy_square_wave <= amplitude;
elsif (noisy_square_wave_base < -amplitude) then
noisy_square_wave <= -amplitude;
else
noisy_square_wave <= noisy_square_wave_base;
end if;
end process;
explosion_base <= noisy_square_wave + voices(2) / 64; -- add extra high-freq small noise
-- quick ADSR to control explosion level enveloppe
thrust_level : process(clock_50)
type t_stage is (s_wait, s_attack, s_decay, s_sustain, s_release);
variable stage : t_stage := s_wait;
constant attack : integer range 0 to 32767 := 500;
constant decay : integer range 0 to 32767 := 2000;
constant sustain : integer range 0 to 32767 := 0;
constant release : integer range 0 to 32767 := 10000;
constant inc_1 : integer range 0 to 32767 := 65; -- ( 0-32767)/500 ~= 65
constant dec_1 : integer range 0 to 32767 := 10; -- (32767-20000)/2000 ~= 7
constant dec_2 : integer range 0 to 32767 := 1; -- (12767-0 )/10000 ~= 1
variable level : integer range 0 to 32767 := 0;
constant attack : integer range 0 to 32767 := 250;
constant decay : integer range 0 to 32767 := 200;
constant sustain : integer range 0 to 32767 := 4000;
constant release : integer range 0 to 32767 := 31100;
constant inc_1 : integer range 0 to 32767 := 130;
constant dec_1 : integer range 0 to 32767 := 7;
constant dec_2 : integer range 0 to 32767 := 1;
variable level : integer range 0 to 32767 := 0;
variable timer : integer range 0 to 32767 := 0;
variable update_level : std_logic;
begin
@@ -256,16 +338,18 @@ begin
timer := timer - 1;
end if;
end if;
-- always wait for explosion trigger
explosion_cmd_r <= sound_switch(4);
if explosion_cmd_r = '0' and sound_switch(4) = '1' then
stage := s_attack;
timer := attack; -- set attack duration
end if;
case stage is
when s_wait => -- wait for explosion trigger
when s_wait =>
level := 0;
explosion_cmd_r <= sound_switch(4);
if explosion_cmd_r = '0' and sound_switch(4) = '1' then
stage := s_attack;
timer := attack; -- set attack duration
end if;
when s_attack => -- increment level during attack
if update_level = '1' then
@@ -304,7 +388,7 @@ begin
end case;
explosion <= ((voices(2)/2)*level)/32768; -- apply enveloppe
explosion <= ((explosion_base/2)*level)/32768; -- apply enveloppe
end if;