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sound, improved and optimized reimplementation of libretro lowpass filter

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This commit is contained in:
kub 2020-12-21 23:22:00 +01:00
parent b437951ade
commit 30969671e5
5 changed files with 141 additions and 123 deletions
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117
pico/sound/mix_arm.S
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@ -154,34 +154,46 @@ m16_32_s2_no_unal2:
@ limit
@ reg=int_sample, lr=1, r3=tmp, kills flags
@ reg=int_sample, r12=1, r8=tmp, kills flags
.macro Limit reg
add r3, lr, \reg, asr #15
bics r3, r3, #1 @ in non-overflow conditions r3 is 0 or 1
sub \reg, \reg, \reg, asr #2 @ reduce audio lvl some to avoid clipping
add r8, r12, \reg, asr #15
bics r8, r8, #1 @ in non-overflow conditions r8 is 0 or 1
movne \reg, #0x8000
subpl \reg, \reg, #1
.endm
@ limit and shift up by 16
@ reg=int_sample, lr=1, r3=tmp, kills flags
@ reg=int_sample, r12=1, r8=tmp, kills flags
.macro Limitsh reg
add r3, lr, \reg, asr #15
bics r3, r3, #1 @ in non-overflow conditions r3 is 0 or 1
sub \reg, \reg, \reg, asr #2 @ reduce audio lvl some to avoid clipping
add r8, r12,\reg, asr #15
bics r8, r8, #1 @ in non-overflow conditions r8 is 0 or 1
moveq \reg, \reg, lsl #16
movne \reg, #0x80000000
subpl \reg, \reg, #0x00010000
.endm
@ filter out DC offset
@ in=int_sample (max 20 bit), y=filter memory, r3=tmp
@ in=int_sample (max 20 bit), y=filter memory, r8=tmp
.macro DCfilt in y
rsb r3, \y, \in, lsl #12 @ fixpoint 20.12
add \y, \y, r3, asr #13
sub r3, r3, r3, asr #2 @ reduce audio lvl some
asr \in, r3, #12
rsb r8, \y, \in, lsl #12 @ fixpoint 20.12
add \y, \y, r8, asr #12 @ alpha = 1-1/4094
sub \in, \in, \y, asr #12
.endm
@ lowpass filter
@ in=int_sample (max 20 bit), y=filter memory, r12=alpha(Q8), r8=tmp
.macro LPfilt in y
@ asr r8, \y, #8
@ rsb r8, r8, \in, lsl #4 @ fixpoint 20.12
sub r8, \in, \y, asr #12 @ fixpoint 20.12
mla \y, r8, r12, \y
asr \in, \y, #12
.endm
@ mix 32bit audio (with 16bits really used, upper bits indicate overflow) with normal 16 bit audio with left channel only
@ warning: this function assumes dest is word aligned
.global mix_32_to_16l_stereo @ short *dest, int *src, int count
@ -193,9 +205,10 @@ mix_32_to_16l_stereo:
subs r2, r2, #4
bmi m32_16l_st_end
mov lr, #1
ldr r12, =filter
ldmia r12, {r10-r11}
ldr r8, [r12], #4
ldmia r12, {r3,r10-r11,lr}
str r8, [sp, #-4]!
m32_16l_st_loop:
ldmia r0, {r8,r12}
@ -206,10 +219,16 @@ m32_16l_st_loop:
add r5, r5, r8, asr #16
add r6, r6, r12,asr #16
add r7, r7, r12,asr #16
ldr r12,[sp]
LPfilt r4, r3
LPfilt r5, lr
LPfilt r6, r3
LPfilt r7, lr
DCfilt r4, r10
DCfilt r5, r11
DCfilt r6, r10
DCfilt r7, r11
mov r12,#1
Limitsh r4
Limitsh r5
Limitsh r6
@ -228,8 +247,12 @@ m32_16l_st_end:
ldmia r1!,{r4,r5}
add r4, r4, r6
add r5, r5, r6
ldr r12,[sp]
LPfilt r4, r3
LPfilt r5, lr
DCfilt r4, r10
DCfilt r5, r11
mov r12,#1
Limitsh r4
Limitsh r5
orr r4, r5, r4, lsr #16
@ -237,7 +260,9 @@ m32_16l_st_end:
m32_16l_st_no_unal2:
ldr r12, =filter
stmia r12, {r10-r11}
add r12,r12, #4
stmia r12, {r3,r10-r11,lr}
add sp, sp, #4
ldmfd sp!, {r4-r8,r10-r11,lr}
bx lr
@ -248,9 +273,10 @@ m32_16l_st_no_unal2:
mix_32_to_16_mono:
stmfd sp!, {r4-r8,r10-r11,lr}
mov lr, #1
ldr r12, =filter
ldr r10, [r12]
ldr r8, [r12], #4
ldmia r12, {r10-r11}
str r8, [sp, #-4]!
@ check if dest is word aligned
tst r0, #2
@ -259,6 +285,10 @@ mix_32_to_16_mono:
ldr r4, [r1], #4
sub r2, r2, #1
add r4, r4, r5
ldr r12,[sp]
LPfilt r4, r11
DCfilt r4, r10
mov r12,#1
Limit r4
strh r4, [r0], #2
@ -275,10 +305,16 @@ m32_16_mo_loop:
add r7, r7, r12,asr #16
mov r12,r12,lsl #16
add r6, r6, r12,asr #16
ldr r12,[sp]
LPfilt r4, r11
LPfilt r5, r11
LPfilt r6, r11
LPfilt r7, r11
DCfilt r4, r10
DCfilt r5, r10
DCfilt r6, r10
DCfilt r7, r10
mov r12,#1
Limitsh r4
Limitsh r5
Limitsh r6
@ -298,8 +334,12 @@ m32_16_mo_end:
add r5, r5, r6, asr #16
mov r6, r6, lsl #16
add r4, r4, r6, asr #16
ldr r12,[sp]
LPfilt r4, r11
LPfilt r5, r11
DCfilt r4, r10
DCfilt r5, r10
mov r12,#1
Limitsh r4
Limitsh r5
orr r4, r5, r4, lsr #16
@ -311,13 +351,18 @@ m32_16_mo_no_unal2:
ldrsh r5, [r0]
ldr r4, [r1], #4
add r4, r4, r5
ldr r12,[sp]
LPfilt r4, r11
DCfilt r4, r10
mov r12,#1
Limit r4
strh r4, [r0], #2
m32_16_mo_no_unal:
ldr r12, =filter
str r10, [r12]
add r12,r12, #4
stmia r12, {r10-r11}
add sp, sp, #4
ldmfd sp!, {r4-r8,r10-r11,lr}
bx lr
@ -344,7 +389,9 @@ mix_32_to_16l_stereo_lvl:
mov lr, #1
ldr r9, [r9]
ldr r12, =filter
ldm r12, {r10-r11}
ldr r8, [r12], #4
ldmia r12, {r3,r10-r11,lr}
str r8, [sp, #-4]!
mov r2, r2, lsl #1
subs r2, r2, #4
@ -363,10 +410,16 @@ m32_16l_st_l_loop:
mov r5, r5, asr r9
mov r6, r6, asr r9
mov r7, r7, asr r9
ldr r12,[sp]
LPfilt r4, r3
LPfilt r5, lr
LPfilt r6, r3
LPfilt r7, lr
DCfilt r4, r10
DCfilt r5, r11
DCfilt r6, r10
DCfilt r7, r11
mov r12,#1
Limitsh r4
Limitsh r5
Limitsh r6
@ -387,8 +440,12 @@ m32_16l_st_l_end:
add r5, r5, r6
mov r4, r4, asr r9
mov r5, r5, asr r9
ldr r12,[sp]
LPfilt r4, r3
LPfilt r5, lr
DCfilt r4, r10
DCfilt r5, r11
mov r12,#1
Limitsh r4
Limitsh r5
orr r4, r5, r4, lsr #16
@ -396,22 +453,32 @@ m32_16l_st_l_end:
m32_16l_st_l_no_unal2:
ldr r12, =filter
stmia r12, {r10-r11}
add r12,r12, #4
stmia r12, {r3,r10-r11,lr}
add sp, sp, #4
ldmfd sp!, {r4-r11,lr}
bx lr
#endif /* __GP2X__ */
.global mix_reset @ void
.global mix_reset @ int alpha_q16
mix_reset:
ldr r0, =filter
ldr r2, =filter
rsb r0, r0, #0x10000
@ asr r0, r0, #8
asr r0, r0, #4
str r0, [r2], #4
mov r1, #0
str r1, [r0]
str r1, [r0, #4]
str r1, [r2], #4
str r1, [r2], #4
str r1, [r2], #4
str r1, [r2], #4
bx lr
.data
filter:
.ds 8
.ds 4 @ alpha_q8
.ds 8 @ filter history for left channel
.ds 8 @ filter history for right channel
@ vim:filetype=armasm