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Add optional low pass audio filter (#87)

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jdgleaver 2022-04-08 16:12:40 +01:00 committed by GitHub
parent b382d718b0
commit c3faf964cc
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2 changed files with 55 additions and 0 deletions
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41
libretro.c
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@ -177,6 +177,29 @@ static void retro_60hz_cache_audio_samples(int16_t *samples, int32_t frames)
retro_60hz_audio.samples_buf_pos += samples_to_write;
}
static bool audio_low_pass_enabled = false;
static int64_t audio_low_pass_acc_left = 0;
static int64_t audio_low_pass_acc_right = 0;
static void audio_low_pass_apply(int16_t *samples, int32_t frames)
{
while (frames-- > 0)
{
int64_t drop_current_left;
int64_t drop_current_right;
/* Left channel */
drop_current_left = ((*samples << 16) - audio_low_pass_acc_left) >> 3;
audio_low_pass_acc_left += drop_current_left;
*samples++ = (int16_t)((audio_low_pass_acc_left >> 16) & 0xFFFF);
/* Right channel */
drop_current_right = ((*samples << 16) - audio_low_pass_acc_right) >> 3;
audio_low_pass_acc_right += drop_current_right;
*samples++ = (int16_t)((audio_low_pass_acc_right >> 16) & 0xFFFF);
}
}
/* Mono palettes */
struct ws_mono_palette
@ -437,6 +460,10 @@ static void Emulate(EmulateSpecStruct *espec,
espec->SoundBufSize = WSwan_SoundFlush(&audio_samples_buf,
&audio_samples_buf_size);
if (audio_low_pass_enabled)
audio_low_pass_apply(audio_samples_buf,
espec->SoundBufSize);
espec->MasterCycles = v30mz_timestamp;
v30mz_timestamp = 0;
@ -890,6 +917,17 @@ static void check_variables(int startup)
}
}
var.key = "wswan_sound_low_pass";
var.value = NULL;
if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
{
if (!strcmp(var.value, "disabled"))
audio_low_pass_enabled = false;
else if (!strcmp(var.value, "enabled"))
audio_low_pass_enabled = true;
}
if (startup)
{
var.key = "wswan_gfx_colors";
@ -936,6 +974,9 @@ void retro_init(void)
retro_audio_buff_underrun = false;
audio_latency = 0;
update_audio_latency = false;
audio_low_pass_enabled = false;
audio_low_pass_acc_left = 0;
audio_low_pass_acc_right = 0;
check_system_specs();
check_variables(true);

14
libretro_core_options.h
View File

@ -211,6 +211,20 @@ struct retro_core_option_v2_definition option_defs_us[] = {
},
"44100",
},
{
"wswan_sound_low_pass",
"Audio Filter",
NULL,
"Apply a low pass audio filter to 'soften' the sometimes harsh chiptunes produced by the WonderSwan.",
NULL,
NULL,
{
{ "disabled", NULL },
{ "enabled", NULL },
{ NULL, NULL },
},
"disabled",
},
{ NULL, NULL, NULL, NULL, NULL, NULL, {{0}}, NULL },
};