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Fix audiomixer phase inversion and use DSP on Cortex-M33 #11617

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Merged
tannewt merged 2 commits into from
Oct 16, 2026
Merged

Fix audiomixer phase inversion and use DSP on Cortex-M33 #11617

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11a3298
Fix audiomixer inverting samples at level 1.0
lynt-smitka Oct 15, 2026
fc57c0f
Use the DSP mixer path on every core that has it
lynt-smitka Oct 15, 2026
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28 changes: 14 additions & 14 deletions shared-module/audiomixer/Mixer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -72,7 +72,7 @@ void audiomixer_mixer_reset_buffer(audiomixer_mixer_obj_t *self,

__attribute__((always_inline))
static inline uint32_t add16signed(uint32_t a, uint32_t b) {
#if (defined(__ARM_ARCH_7EM__) && (__ARM_ARCH_7EM__ == 1))
#if defined(__ARM_FEATURE_DSP) && __ARM_FEATURE_DSP
return __QADD16(a, b);
#else
uint32_t result = 0;
Expand All @@ -93,12 +93,13 @@ static inline uint32_t add16signed(uint32_t a, uint32_t b) {

__attribute__((always_inline))
static inline uint32_t mult16signed(uint32_t val, int32_t lomul, int32_t himul) {
#if (defined(__ARM_ARCH_7EM__) && (__ARM_ARCH_7EM__ == 1))
lomul <<= 16;
himul <<= 16;
#if defined(__ARM_FEATURE_DSP) && __ARM_FEATURE_DSP
// A level of 1.0 is 1 << 15, so shifting by 16 would overflow into the sign bit.
lomul <<= 15;
himul <<= 15;
int32_t hi, lo;
enum { bits = 16 }; // saturate to 16 bits
enum { shift = 15 }; // shift is done automatically
enum { shift = 14 }; // smulw shifts by 16, so 14 more gives (val * mul) >> 15
__asm__ volatile ("smulwb %0, %1, %2" : "=r" (lo) : "r" (lomul), "r" (val));
__asm__ volatile ("smulwt %0, %1, %2" : "=r" (hi) : "r" (himul), "r" (val));
__asm__ volatile ("ssat %0, %1, %2, asr %3" : "=r" (lo) : "I" (bits), "r" (lo), "I" (shift));
Expand All @@ -108,9 +109,8 @@ static inline uint32_t mult16signed(uint32_t val, int32_t lomul, int32_t himul)
#else
uint32_t result = 0;
for (int8_t i = 0; i < 2; i++) {
float mod_mul = (float)(i ? himul : lomul) / (float)((1 << 15) - 1);
int16_t ai = (val >> (sizeof(uint16_t) * 8 * i));
int32_t intermediate = (int32_t)(ai * mod_mul);
int32_t intermediate = (ai * (i ? himul : lomul)) >> 15;
if (intermediate > SHRT_MAX) {
intermediate = SHRT_MAX;
} else if (intermediate < SHRT_MIN) {
Expand All @@ -124,23 +124,23 @@ static inline uint32_t mult16signed(uint32_t val, int32_t lomul, int32_t himul)
}

static inline uint32_t tounsigned8(uint32_t val) {
#if (defined(__ARM_ARCH_7EM__) && (__ARM_ARCH_7EM__ == 1))
#if defined(__ARM_FEATURE_DSP) && __ARM_FEATURE_DSP
return __UADD8(val, 0x80808080);
#else
return val ^ 0x80808080;
#endif
}

static inline uint32_t tounsigned16(uint32_t val) {
#if (defined(__ARM_ARCH_7EM__) && (__ARM_ARCH_7EM__ == 1))
#if defined(__ARM_FEATURE_DSP) && __ARM_FEATURE_DSP
return __UADD16(val, 0x80008000);
#else
return val ^ 0x80008000;
#endif
}

static inline uint32_t tosigned16(uint32_t val) {
#if (defined(__ARM_ARCH_7EM__) && (__ARM_ARCH_7EM__ == 1))
#if defined(__ARM_FEATURE_DSP) && __ARM_FEATURE_DSP
return __UADD16(val, 0x80008000);
#else
return val ^ 0x80008000;
Expand All @@ -156,7 +156,7 @@ static inline uint32_t pack8(uint32_t val) {
}

static inline uint32_t copy16lsb(uint32_t val) {
#if (defined(__ARM_ARCH_7EM__) && (__ARM_ARCH_7EM__ == 1))
#if defined(__ARM_FEATURE_DSP) && __ARM_FEATURE_DSP
return __PKHBT(val, val, 16);
#else
val &= 0x0000ffff;
Expand All @@ -165,7 +165,7 @@ static inline uint32_t copy16lsb(uint32_t val) {
}

static inline uint32_t copy16msb(uint32_t val) {
#if (defined(__ARM_ARCH_7EM__) && (__ARM_ARCH_7EM__ == 1))
#if defined(__ARM_FEATURE_DSP) && __ARM_FEATURE_DSP
return __PKHTB(val, val, 16);
#else
val &= 0xffff0000;
Expand Down Expand Up @@ -259,9 +259,9 @@ static void mix_down_one_voice(audiomixer_mixer_obj_t *self,
uint16_t left_panning_scaled = 32768, right_panning_scaled = 32768;
if (MP_LIKELY(self->base.channel_count == 2)) {
if (panning >= 0) {
left_panning_scaled = 32767 - panning;
left_panning_scaled = 32768 - panning;
} else {
right_panning_scaled = 32767 + panning;
right_panning_scaled = 32768 + panning;
}
}

Expand Down
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