* See COPYING file in the top-level directory.
*/
+#include "string.h"
+
#define MAXOUT (+32767)
#define MINOUT (-32768)
/* limitter */
-#define Limit(val, max,min) { \
- if ( val > max ) val = max; \
- else if ( val < min ) val = min; \
+#define Limit16(val) { \
+ val -= (val >> 2); \
+ if ((short)val != val) val = (val < 0 ? MINOUT : MAXOUT); \
}
int mix_32_to_16l_level;
-void mix_32_to_16l_stereo_core(short *dest, int *src, int count, int level)
+static struct iir2 { // 2-pole IIR
+ int x[2]; // sample buffer
+ int y[2]; // filter intermediates
+} lfi2, rfi2;
+
+// NB ">>" rounds to -infinity, "/" to 0. To compensate the effect possibly use
+// "-(-y>>n)" (round to +infinity) instead of "y>>n" in places.
+
+// NB uses Q12 fixpoint; samples mustn't have more than 20 bits for this.
+#define QB 12
+
+
+// exponential moving average filter for DC filtering
+// y[n] = (x[n]-y[n-1])*(1/8192) (corner approx. 20Hz, gain 1)
+static inline int filter_exp(struct iir2 *fi2, int x)
{
- int l, r;
+ int xf = (x<<QB) - fi2->y[0];
+ fi2->y[0] += xf >> 13;
+ xf -= xf >> 2; // level reduction to avoid clipping from overshoot
+ return xf>>QB;
+}
- for (; count > 0; count--)
- {
- l = r = *dest;
- l += *src++ >> level;
- r += *src++ >> level;
- Limit( l, MAXOUT, MINOUT );
- Limit( r, MAXOUT, MINOUT );
- *dest++ = l;
- *dest++ = r;
- }
+// unfiltered (for testing)
+static inline int filter_null(struct iir2 *fi2, int x)
+{
+ return x;
+}
+
+#define mix_32_to_16l_stereo_core(dest, src, count, lv, fl) { \
+ int l, r; \
+ \
+ for (; count > 0; count--) \
+ { \
+ l = r = *dest; \
+ l += *src++ >> lv; \
+ r += *src++ >> lv; \
+ l = fl(&lfi2, l); \
+ r = fl(&rfi2, r); \
+ Limit16(l); \
+ Limit16(r); \
+ *dest++ = l; \
+ *dest++ = r; \
+ } \
}
void mix_32_to_16l_stereo_lvl(short *dest, int *src, int count)
{
- mix_32_to_16l_stereo_core(dest, src, count, mix_32_to_16l_level);
+ mix_32_to_16l_stereo_core(dest, src, count, mix_32_to_16l_level, filter_exp);
}
void mix_32_to_16l_stereo(short *dest, int *src, int count)
{
- mix_32_to_16l_stereo_core(dest, src, count, 0);
+ mix_32_to_16l_stereo_core(dest, src, count, 0, filter_exp);
}
void mix_32_to_16_mono(short *dest, int *src, int count)
{
l = *dest;
l += *src++;
- Limit( l, MAXOUT, MINOUT );
+ l = filter_exp(&lfi2, l);
+ Limit16(l);
*dest++ = l;
}
}
}
}
+void mix_reset(void)
+{
+ memset(&lfi2, 0, sizeof(lfi2));
+ memset(&rfi2, 0, sizeof(rfi2));
+}
@ limit and shift up by 16
@ reg=int_sample, lr=1, r3=tmp, kills flags
.macro Limitsh reg
-@ movs r4, r3, asr #16
-@ cmnne r4, #1
-@ beq c32_16_no_overflow
-@ tst r4, r4
-@ mov r3, #0x8000
-@ subpl r3, r3, #1
-
add r3, lr, \reg, asr #15
bics r3, r3, #1 @ in non-overflow conditions r3 is 0 or 1
moveq \reg, \reg, lsl #16
subpl \reg, \reg, #0x00010000
.endm
+@ filter out DC offset
+@ in=int_sample (max 20 bit), y=filter memory, r3=tmp
+.macro DCfilt in y
+ rsb r3, \y, \in, asl #12 @ fixpoint 20.12
+ add \y, \y, r3, asr #13
+ sub \in, \in, \y, asr #12
+ sub \in, \in, \in, asr #2 @ reduce audio lvl some
+.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
mix_32_to_16l_stereo:
- stmfd sp!, {r4-r8,lr}
-
- mov lr, #1
+ stmfd sp!, {r4-r8,r10-r11,lr}
mov r2, r2, lsl #1
subs r2, r2, #4
bmi m32_16l_st_end
+ mov lr, #1
+ ldr r12, =filter
+ ldmia r12, {r10-r11}
+
m32_16l_st_loop:
ldmia r0, {r8,r12}
ldmia r1!, {r4-r7}
add r5, r5, r8, asr #16
add r6, r6, r12,asr #16
add r7, r7, r12,asr #16
+ DCfilt r4, r10
+ DCfilt r5, r11
+ DCfilt r6, r10
+ DCfilt r7, r11
Limitsh r4
Limitsh r5
Limitsh r6
ldmia r1!,{r4,r5}
add r4, r4, r6
add r5, r5, r6
+ DCfilt r4, r10
+ DCfilt r5, r11
Limitsh r4
Limitsh r5
orr r4, r5, r4, lsr #16
str r4, [r0], #4
m32_16l_st_no_unal2:
- ldmfd sp!, {r4-r8,lr}
+ ldr r12, =filter
+ stmia r12, {r10-r11}
+ ldmfd sp!, {r4-r8,r10-r11,lr}
bx lr
.global mix_32_to_16_mono @ short *dest, int *src, int count
mix_32_to_16_mono:
- stmfd sp!, {r4-r8,lr}
+ stmfd sp!, {r4-r8,r10-r11,lr}
mov lr, #1
+ ldr r12, =filter
+ ldr r10, [r12]
@ check if dest is word aligned
tst r0, #2
add r7, r7, r12,asr #16
mov r12,r12,lsl #16
add r6, r6, r12,asr #16
+ DCfilt r4, r10
+ DCfilt r5, r10
+ DCfilt r6, r10
+ DCfilt r7, r10
Limitsh r4
Limitsh r5
Limitsh r6
add r5, r5, r6, asr #16
mov r6, r6, lsl #16
add r4, r4, r6, asr #16
+ DCfilt r4, r10
+ DCfilt r5, r10
Limitsh r4
Limitsh r5
orr r4, r5, r4, lsr #16
m32_16_mo_no_unal2:
tst r2, #1
- ldmeqfd sp!, {r4-r8,pc}
+ beq m32_16_mo_no_unal
ldrsh r5, [r0]
ldr r4, [r1], #4
add r4, r4, r5
+ DCfilt r4, r10
Limit r4
strh r4, [r0], #2
- ldmfd sp!, {r4-r8,lr}
+m32_16_mo_no_unal:
+ ldr r12, =filter
+ str r10, [r12]
+ ldmfd sp!, {r4-r8,r10-r11,lr}
bx lr
.global mix_32_to_16l_stereo_lvl @ short *dest, int *src, int count
mix_32_to_16l_stereo_lvl:
- stmfd sp!, {r4-r9,lr}
+ stmfd sp!, {r4-r11,lr}
ldr r9, =mix_32_to_16l_level
mov lr, #1
ldr r9, [r9]
+ ldr r12, =filter
+ ldm r12, {r10-r11}
mov r2, r2, lsl #1
subs r2, r2, #4
mov r5, r5, asr r9
mov r6, r6, asr r9
mov r7, r7, asr r9
+ DCfilt r4, r10
+ DCfilt r5, r11
+ DCfilt r6, r10
+ DCfilt r7, r11
Limitsh r4
Limitsh r5
Limitsh r6
add r5, r5, r6
mov r4, r4, asr r9
mov r5, r5, asr r9
+ DCfilt r4, r10
+ DCfilt r5, r11
Limitsh r4
Limitsh r5
orr r4, r5, r4, lsr #16
str r4, [r0], #4
m32_16l_st_l_no_unal2:
- ldmfd sp!, {r4-r9,lr}
+ ldr r12, =filter
+ stmia r12, {r10-r11}
+ ldmfd sp!, {r4-r11,lr}
+ bx lr
+
+.global mix_reset @ void
+mix_reset:
+ ldr r0, =filter
+ mov r1, #0
+ str r1, [r0]
+ str r1, [r0, #4]
bx lr
+.data
+ DCfilt r4, r10
+ DCfilt r5, r11
+filter:
+ .ds 8
+
#endif /* __GP2X__ */
@ vim:filetype=armasm
notaz.gp2x.de / picodrive.git / commitdiff