From f6c4dec60e6e2c39c4c696ccff6eeda075378d31 Mon Sep 17 00:00:00 2001
From: neonloop
Date: Fri, 25 Mar 2022 21:33:00 +0000
Subject: Adds passthrough resampler when core rate is supported

Small improvement to performance
---
 plat.h        |  2 +-
 plat_linux.c  |  2 +-
 plat_sdl.c    | 50 +++++++++++++++++++++++++++++++++++++++++++++-----
 plat_trimui.c |  2 +-
 4 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/plat.h b/plat.h
index 9a0d969..fdcb1a9 100644
--- a/plat.h
+++ b/plat.h
@@ -28,7 +28,7 @@ void plat_video_close(void);
 unsigned plat_cpu_ticks(void);
 
 float plat_sound_capacity(void);
-void plat_sound_write(const struct audio_frame *data, int frames);
+extern void (*plat_sound_write)(const struct audio_frame *data, int frames);
 void plat_sound_resize_buffer(void);
 
 #endif /* __PLAT_H__ */
diff --git a/plat_linux.c b/plat_linux.c
index bc57f3c..edccce6 100644
--- a/plat_linux.c
+++ b/plat_linux.c
@@ -6,7 +6,7 @@
 #include "main.h"
 #include "util.h"
 
-#define SAMPLE_RATE 48000
+#define MAX_SAMPLE_RATE 65536
 
 static const struct in_default_bind in_sdl_defbinds[] = {
 	{ SDLK_UP,        IN_BINDTYPE_PLAYER12, RETRO_DEVICE_ID_JOYPAD_UP },
diff --git a/plat_sdl.c b/plat_sdl.c
index 0596ce7..5d996b3 100644
--- a/plat_sdl.c
+++ b/plat_sdl.c
@@ -22,6 +22,9 @@ struct audio_state {
 
 struct audio_state audio;
 
+static void plat_sound_select_resampler(void);
+void (*plat_sound_write)(const struct audio_frame *data, int frames);
+
 static char msg[HUD_LEN];
 static unsigned msg_priority = 0;
 static unsigned msg_expire = 0;
@@ -49,6 +52,13 @@ static void video_print_msg(uint16_t *dst, uint32_t h, uint32_t pitch, char *msg
 	basic_text_out16_nf(dst, pitch, 2, h - 10, msg);
 }
 
+static int audio_resample_passthrough(struct audio_frame data) {
+	audio.buf[audio.buf_w++] = data;
+	if (audio.buf_w >= audio.buf_len) audio.buf_w = 0;
+
+	return 1;
+}
+
 static int audio_resample_nearest(struct audio_frame data) {
 	static int diff = 0;
 	int consumed = 0;
@@ -295,7 +305,7 @@ static int plat_sound_init(void)
 
 	SDL_AudioSpec spec, received;
 
-	spec.freq = SAMPLE_RATE;
+	spec.freq = MIN(sample_rate, MAX_SAMPLE_RATE);
 	spec.format = AUDIO_S16;
 	spec.channels = 2;
 	spec.samples = 512;
@@ -308,6 +318,7 @@ static int plat_sound_init(void)
 
 	audio.in_sample_rate = sample_rate;
 	audio.out_sample_rate = received.freq;
+	plat_sound_select_resampler();
 	plat_sound_resize_buffer();
 
 	SDL_PauseAudio(0);
@@ -330,7 +341,7 @@ float plat_sound_capacity(void)
 }
 
 #define BATCH_SIZE 100
-void plat_sound_write(const struct audio_frame *data, int frames)
+void plat_sound_write_resample(const struct audio_frame *data, int frames, int (*resample)(struct audio_frame data))
 {
 	int consumed = 0;
 	if (audio.buf_len == 0)
@@ -354,7 +365,7 @@ void plat_sound_write(const struct audio_frame *data, int frames)
 		}
 
 		while (amount && audio.buf_w != audio.max_buf_w) {
-			consumed = audio_resample_nearest(*data);
+			consumed = resample(*data);
 			data += consumed;
 			amount -= consumed;
 			frames -= consumed;
@@ -363,6 +374,16 @@ void plat_sound_write(const struct audio_frame *data, int frames)
 	SDL_UnlockAudio();
 }
 
+void plat_sound_write_passthrough(const struct audio_frame *data, int frames)
+{
+	plat_sound_write_resample(data, frames, audio_resample_passthrough);
+}
+
+void plat_sound_write_nearest(const struct audio_frame *data, int frames)
+{
+	plat_sound_write_resample(data, frames, audio_resample_nearest);
+}
+
 void plat_sound_resize_buffer(void) {
 	size_t buf_size;
 	SDL_LockAudio();
@@ -393,12 +414,25 @@ void plat_sound_resize_buffer(void) {
 	SDL_UnlockAudio();
 }
 
+static void plat_sound_select_resampler(void)
+{
+	if (audio.in_sample_rate == audio.out_sample_rate) {
+		PA_INFO("Using passthrough resampler (in: %d, out: %d)\n", audio.in_sample_rate, audio.out_sample_rate);
+		plat_sound_write = plat_sound_write_passthrough;
+	} else {
+		PA_INFO("Using nearest resampler (in: %d, out: %d)\n", audio.in_sample_rate, audio.out_sample_rate);
+		plat_sound_write = plat_sound_write_nearest;
+	}
+}
+
 void plat_sdl_event_handler(void *event_)
 {
 }
 
 int plat_init(void)
 {
+	plat_sound_write = plat_sound_write_nearest;
+
 	SDL_Init(SDL_INIT_VIDEO);
 	screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP * 8, SDL_SWSURFACE);
 	if (screen == NULL) {
@@ -432,8 +466,14 @@ int plat_init(void)
 
 int plat_reinit(void)
 {
-	audio.in_sample_rate = sample_rate;
-	plat_sound_resize_buffer();
+	if (sample_rate && sample_rate != audio.in_sample_rate) {
+		plat_sound_finish();
+
+		if (plat_sound_init()) {
+			PA_ERROR("SDL sound failed to init: %s\n", SDL_GetError());
+			return -1;
+		}
+	}
 	scale_update_scaler();
 	return 0;
 }
diff --git a/plat_trimui.c b/plat_trimui.c
index eee7c19..a60c7fb 100644
--- a/plat_trimui.c
+++ b/plat_trimui.c
@@ -6,7 +6,7 @@
 #include "main.h"
 #include "util.h"
 
-#define SAMPLE_RATE 48000
+#define MAX_SAMPLE_RATE 48000
 
 static const struct in_default_bind in_sdl_defbinds[] = {
 	{ SDLK_UP,        IN_BINDTYPE_PLAYER12, RETRO_DEVICE_ID_JOYPAD_UP },
-- 
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