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diff --git a/libretro/libretro.c b/libretro/libretro.c
index 81ce4aa..3c24e8f 100644
--- a/libretro/libretro.c
+++ b/libretro/libretro.c
@@ -96,6 +96,21 @@ bool8 ROMAPUEnabled = 0;
bool overclock_cycles = false;
int one_c, slow_one_c, two_c;
+static unsigned frameskip_type = 0;
+static unsigned frameskip_threshold = 0;
+static uint16_t frameskip_counter = 0;
+static unsigned frameskip_interval = 0;
+
+static bool retro_audio_buff_active = false;
+static unsigned retro_audio_buff_occupancy = 0;
+static bool retro_audio_buff_underrun = false;
+/* Maximum number of consecutive frames that
+ * can be skipped */
+#define FRAMESKIP_MAX 30
+
+static unsigned retro_audio_latency = 0;
+static bool update_audio_latency = false;
+
static memstream_t *s_stream = NULL;
static int s_open(const char *fname, const char *mode)
@@ -208,6 +223,57 @@ void retro_get_system_info(struct retro_system_info *info)
info->block_extract = false;
}
+static void retro_audio_buff_status_cb(
+ bool active, unsigned occupancy, bool underrun_likely)
+{
+ retro_audio_buff_active = active;
+ retro_audio_buff_occupancy = occupancy;
+ retro_audio_buff_underrun = underrun_likely;
+}
+
+static void retro_set_audio_buff_status_cb(void)
+{
+ if (frameskip_type > 0)
+ {
+ struct retro_audio_buffer_status_callback buf_status_cb;
+
+ buf_status_cb.callback = retro_audio_buff_status_cb;
+ if (!environ_cb(RETRO_ENVIRONMENT_SET_AUDIO_BUFFER_STATUS_CALLBACK,
+ &buf_status_cb))
+ {
+ retro_audio_buff_active = false;
+ retro_audio_buff_occupancy = 0;
+ retro_audio_buff_underrun = false;
+ retro_audio_latency = 0;
+ }
+ else
+ {
+ /* Frameskip is enabled - increase frontend
+ * audio latency to minimise potential
+ * buffer underruns */
+ uint32_t frame_time_usec = Settings.FrameTime;
+
+ if (Settings.ForceNTSC)
+ frame_time_usec = Settings.FrameTimeNTSC;
+ if (Settings.ForcePAL)
+ frame_time_usec = Settings.FrameTimePAL;
+
+ /* Set latency to 6x current frame time... */
+ retro_audio_latency = (unsigned)(6 * frame_time_usec / 1000);
+
+ /* ...then round up to nearest multiple of 32 */
+ retro_audio_latency = (retro_audio_latency + 0x1F) & ~0x1F;
+ }
+ }
+ else
+ {
+ environ_cb(RETRO_ENVIRONMENT_SET_AUDIO_BUFFER_STATUS_CALLBACK, NULL);
+ retro_audio_latency = 0;
+ }
+
+ update_audio_latency = true;
+}
+
static int16 audio_buf[0x10000];
static unsigned avail;
static float samplerate = 32040.5f;
@@ -339,6 +405,9 @@ void retro_init (void)
{
static const struct retro_variable vars[] =
{
+ { "snes9x2002_frameskip", "Frameskip ; disabled|auto|threshold" },
+ { "snes9x2002_frameskip_threshold", "Frameskip Threshold (%); 30|40|50|60" },
+ { "snes9x2002_frameskip_interval", "Frameskip Interval; 1|2|3|4|5|6|7|8|9" },
{ "snes9x2002_overclock_cycles", "Reduce Slowdown (Hack, Unsafe, Restart); disabled|compatible|max" },
{ NULL, NULL },
};
@@ -383,6 +452,14 @@ void retro_deinit(void)
GFX.SubZBuffer_buffer = NULL;
libretro_supports_bitmasks = false;
+ frameskip_type = 0;
+ frameskip_threshold = 0;
+ frameskip_counter = 0;
+ retro_audio_buff_active = false;
+ retro_audio_buff_occupancy = 0;
+ retro_audio_buff_underrun = false;
+ retro_audio_latency = 0;
+ update_audio_latency = false;
}
void retro_reset (void)
@@ -423,9 +500,42 @@ static void report_buttons (void)
}
}
-static void check_variables(void)
+static void check_variables(bool first_run)
{
struct retro_variable var;
+ bool prev_force_ntsc;
+ bool prev_force_pal;
+ bool prev_frameskip_type;
+
+ var.key = "snes9x2002_frameskip";
+ var.value = NULL;
+
+ prev_frameskip_type = frameskip_type;
+ frameskip_type = 0;
+
+ if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
+ {
+ if (strcmp(var.value, "auto") == 0)
+ frameskip_type = 1;
+ if (strcmp(var.value, "threshold") == 0)
+ frameskip_type = 2;
+ }
+
+ var.key = "snes9x2002_frameskip_threshold";
+ var.value = NULL;
+
+ frameskip_threshold = 30;
+
+ if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
+ frameskip_threshold = strtol(var.value, NULL, 10);
+
+ var.key = "snes9x2002_frameskip_interval";
+ var.value = NULL;
+
+ frameskip_interval = 1;
+
+ if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
+ frameskip_interval = strtol(var.value, NULL, 10);
var.key = "snes9x2002_overclock_cycles";
var.value = NULL;
@@ -449,6 +559,13 @@ static void check_variables(void)
else
overclock_cycles = false;
}
+
+ /* Reinitialise frameskipping, if required */
+ if (!first_run &&
+ ((frameskip_type != prev_frameskip_type) ||
+ (Settings.ForceNTSC != prev_force_ntsc) ||
+ (Settings.ForcePAL != prev_force_pal)))
+ retro_set_audio_buff_status_cb();
}
//#define FRAME_SKIP
@@ -458,7 +575,7 @@ void retro_run (void)
bool updated = false;
if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE_UPDATE, &updated) && updated)
- check_variables();
+ check_variables(false);
#ifdef FRAME_SKIP
IPPU.RenderThisFrame = !IPPU.RenderThisFrame;
@@ -466,6 +583,53 @@ void retro_run (void)
IPPU.RenderThisFrame = TRUE;
#endif
+ /* Check whether current frame should
+ * be skipped */
+ if ((frameskip_type > 0) &&
+ retro_audio_buff_active &&
+ IPPU.RenderThisFrame)
+ {
+ bool skip_frame;
+
+ switch (frameskip_type)
+ {
+ case 1: /* auto */
+ skip_frame = retro_audio_buff_underrun;
+ break;
+ case 2: /* threshold */
+ skip_frame = (retro_audio_buff_occupancy < frameskip_threshold);
+ break;
+ default:
+ skip_frame = false;
+ break;
+ }
+
+ if (skip_frame)
+ {
+ if(frameskip_counter < frameskip_interval)
+ {
+ IPPU.RenderThisFrame = false;
+ frameskip_counter++;
+ }
+ else
+ frameskip_counter = 0;
+ }
+ else
+ frameskip_counter = 0;
+ }
+
+ /* If frameskip/timing settings have changed,
+ * update frontend audio latency
+ * > Can do this before or after the frameskip
+ * check, but doing it after means we at least
+ * retain the current frame's audio output */
+ if (update_audio_latency)
+ {
+ environ_cb(RETRO_ENVIRONMENT_SET_MINIMUM_AUDIO_LATENCY,
+ &retro_audio_latency);
+ update_audio_latency = false;
+ }
+
poll_cb();
report_buttons();
@@ -559,7 +723,7 @@ bool retro_load_game(const struct retro_game_info *game)
bool8 loaded;
enum retro_pixel_format fmt = RETRO_PIXEL_FORMAT_RGB565;
- check_variables();
+ check_variables(true);
if (!environ_cb(RETRO_ENVIRONMENT_SET_PIXEL_FORMAT, &fmt))
return false;
@@ -585,6 +749,7 @@ bool retro_load_game(const struct retro_game_info *game)
memset(audio_buf, 0, sizeof(audio_buf));
+ retro_set_audio_buff_status_cb();
return true;
}
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