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add support for master volume control register

add basic support for per-channel volume controls
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inolen committed May 8, 2017
1 parent 3a2e737 commit 02470dc3d3dcacf240e2056f951a1e77f7747675
Showing with 87 additions and 2 deletions.
  1. +87 −2 src/hw/aica/aica.c
@@ -1,3 +1,4 @@
#include <math.h>
#include "hw/aica/aica.h"
#include "core/log.h"
#include "core/option.h"
@@ -80,6 +81,82 @@ struct aica {
FILE *recording;
};

static int32_t mvol_scale[16];
static int32_t tl_scale[256];

static void aica_init_tables() {
static int initialized = 0;

if (initialized) {
return;
}

initialized = 1;

/* the MVOL register adjusts the output level based on the table:
MVOL ∆level
----------------
0 -MAX db
1 -42 db
2 -39 db
...
n -42 + (n-1) db
sound pressure level is defined as:
∆level = 20 * log10(out / in)
out can therefor be calculated as:
out = in * pow(10, ∆level / 20)
this can be approximated using MVOL instead of ∆level as:
out = in / pow(2, (MVOL - i) / 2) */

for (int i = 0; i < 16; i++) {
/* 0 is a special case that mutes the output */
if (i == 0) {
continue;
}

/* a 32-bit int is used for the scale, leaving 15 bits for the fraction */
mvol_scale[i] = (1 << 15) / pow(2.0f, (15 - i) / 2.0f);
}

/* each channel's TL register adjusts the output level based on the table:
TL ∆level
--------------
bit 0 -0.4 db
bit 1 -0.8 db
bit 2 -1.5 db
bit 3 -3.0 db
bit 4 -6.0 db
bit 5 -12.0 db
bit 6 -24.0 db
bit 7 -48.0 db
this can be approximated using TL as:
out = in / pow(2, TL / 16) */

for (int i = 0; i < 256; i++) {
/* a 32-bit int is used for the scale, leaving 15 bits for the fraction */
tl_scale[i] = (1 << 15) / pow(2.0f, i / 16.0f);
}
}

static inline int32_t aica_adjust_master_volume(struct aica *aica, int32_t in) {
int32_t y = mvol_scale[aica->common_data->MVOL];
/* truncate fraction */
return (in * y) >> 15;
}

static inline int32_t aica_adjust_channel_volume(struct aica_channel *ch,
int32_t in) {
int32_t y = tl_scale[ch->data->TL];
/* truncate fraction */
return (in * y) >> 15;
}

static void aica_decode_adpcm(int32_t data, int32_t prev, int32_t prev_quant,
int32_t *next, int32_t *next_quant) {
/* the decoded value (n) = (1 - 2 * l4) * (l3 + l2/2 + l1/4 + 1/8) * quantized
@@ -381,6 +458,9 @@ static int32_t aica_channel_update(struct aica *aica, struct aica_channel *ch) {

uint32_t pos = AICA_OFFSET_POS(ch->offset);
uint32_t frac = AICA_OFFSET_FRAC(ch->offset);

/* the data returned is a signed 16-bit PCM data, but signed 32-bit values are
used intermediately to avoid dealing with overflows until the end */
int32_t next_sample = 0;
int32_t next_quant = 0;

@@ -452,10 +532,13 @@ static void aica_generate_frames(struct aica *aica, int num_frames) {
for (int j = 0; j < AICA_NUM_CHANNELS; j++) {
struct aica_channel *ch = &aica->channels[j];
int32_t s = aica_channel_update(aica, ch);
l += s;
r += s;
l += aica_adjust_channel_volume(ch, s);
r += aica_adjust_channel_volume(ch, s);
}

l = aica_adjust_master_volume(aica, l);
r = aica_adjust_master_volume(aica, r);

buffer[i * 2 + 0] = CLAMP(l, INT16_MIN, INT16_MAX);
buffer[i * 2 + 1] = CLAMP(r, INT16_MIN, INT16_MAX);
}
@@ -746,6 +829,8 @@ void aica_destroy(struct aica *aica) {
}

struct aica *aica_create(struct dreamcast *dc) {
aica_init_tables();

struct aica *aica = dc_create_device(dc, sizeof(struct aica), "aica",
&aica_init, &aica_debug_menu);
return aica;

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