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From 0ddb31675a8ba2fef40340034b0371b7fb63a8b9 Mon Sep 17 00:00:00 2001
From: "Franc[e]sco" <lolisamurai@tfwno.gf>
Date: Sun, 11 Oct 2020 15:25:28 +0200
Subject: [PATCH 1/2] hw/audio/pcspk: Use a semicircle wave rather than a pure
square wave
---
hw/audio/pcspk.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/hw/audio/pcspk.c b/hw/audio/pcspk.c
index ea539e7605..1545b3c90a 100644
--- a/hw/audio/pcspk.c
+++ b/hw/audio/pcspk.c
@@ -23,6 +23,7 @@
*/
#include "qemu/osdep.h"
+#include <math.h>
#include "hw/isa/isa.h"
#include "hw/audio/soundhw.h"
#include "audio/audio.h"
@@ -61,18 +62,26 @@ typedef struct {
static const char *s_spk = "pcspk";
static PCSpkState *pcspk_state;
+/* a lot less harsh on the ears than a perfect square wave, while still sounding square-ish */
+static inline float circle_wave(float x)
+{
+ int s = (x > 0) - (x < 0);
+ float t = (x * 2 - (s - 1) / 2) * 2 - 1;
+ return -s * sqrtf(1 - t * t);
+}
+
static inline void generate_samples(PCSpkState *s)
{
unsigned int i;
if (s->pit_count) {
const uint32_t m = PCSPK_SAMPLE_RATE * s->pit_count;
- const uint32_t n = ((uint64_t)PIT_FREQ << 32) / m;
+ const float n = (float)PIT_FREQ / m;
/* multiple of wavelength for gapless looping */
s->samples = (QEMU_ALIGN_DOWN(PCSPK_BUF_LEN * PIT_FREQ, m) / (PIT_FREQ >> 1) + 1) >> 1;
for (i = 0; i < s->samples; ++i)
- s->sample_buf[i] = (64 & (n * i >> 25)) - 32;
+ s->sample_buf[i] = 128 + circle_wave(fmod(n * i, 1.f) - .5f) * 16;
} else {
s->samples = PCSPK_BUF_LEN;
for (i = 0; i < PCSPK_BUF_LEN; ++i)
--
2.28.0
|