Begin adding rate control.

audio/rsound.c

@@ -181,6 +181,24 @@ static void rs_free(void *data)
    free(rsd);
 }
 
+static size_t rs_write_avail(void *data)
+{
+   rsd_t *rsd = data;
+
+   if (rsd->has_error)
+      return 0;
+   rsd_callback_lock(rsd->rd);
+   size_t val = fifo_write_avail(rsd->buffer);
+   rsd_callback_unlock(rsd->rd);
+   return val;
+}
+
+static size_t rs_buffer_size(void *data)
+{
+   (void)data;
+   return 1024 * 4;
+}
+
 const audio_driver_t audio_rsound = {
    rs_init,
    rs_write,
@@ -189,6 +207,8 @@ const audio_driver_t audio_rsound = {
    rs_set_nonblock_state,
    rs_free,
    NULL,
-   "rsound"
+   "rsound",
+   rs_write_avail,
+   rs_buffer_size,
 };
    

config.def.h

@@ -231,6 +231,16 @@ static const int out_latency = 64;
 // Will sync audio. (recommended) 
 static const bool audio_sync = true;
 
+// Experimental rate control
+static const bool rate_control = false;
+
+// Rate control delta. Defines how much rate_control is allowed to adjust input rate.
+static const float rate_control_delta = 0.005;
+
+//////////////
+// Misc
+//////////////
+
 // Enables use of rewind. This will incur some memory footprint depending on the save state buffer.
 // This rewind only works when using bSNES core atm.
 static const bool rewind_enable = false;

driver.c

@@ -335,9 +335,21 @@ void init_audio(void)
    ssnes_assert(g_settings.audio.out_rate < g_settings.audio.in_rate * AUDIO_MAX_RATIO);
    ssnes_assert(g_extern.audio_data.outsamples = (float*)malloc(max_bufsamples * sizeof(float) * AUDIO_MAX_RATIO));
 
-   g_extern.audio_data.src_ratio =
+   g_extern.audio_data.orig_src_ratio =
+      g_extern.audio_data.src_ratio =
       (double)g_settings.audio.out_rate / g_settings.audio.in_rate;
 
+   if (g_settings.audio.rate_control)
+   {
+      if (driver.audio->buffer_size && driver.audio->write_avail)
+      {
+         g_extern.audio_data.driver_buffer_size = driver.audio->buffer_size(driver.audio_data);
+         g_extern.audio_data.rate_control = true;
+      }
+      else
+         SSNES_WARN("Audio rate control was desired, but driver does not support needed features.\n");
+   }
+
 #ifdef HAVE_DYLIB
    init_dsp_plugin();
 #endif

driver.h

@@ -98,6 +98,9 @@ typedef struct audio_driver
    void (*free)(void *data);
    bool (*use_float)(void *data); // Defines if driver will take standard floating point samples, or int16_t samples.
    const char *ident;
+
+   size_t (*write_avail)(void *data); // Optional
+   size_t (*buffer_size)(void *data); // Optional
 } audio_driver_t;
 
 #define AXIS_NEG(x) (((uint32_t)(x) << 16) | UINT16_C(0xFFFF))

general.h

@@ -138,6 +138,9 @@ struct settings
 
       char dsp_plugin[PATH_MAX];
       char external_driver[PATH_MAX];
+
+      bool rate_control;
+      float rate_control_delta;
    } audio;
 
    struct
@@ -299,6 +302,10 @@ struct global
       dylib_t dsp_lib;
       const ssnes_dsp_plugin_t *dsp_plugin;
       void *dsp_handle;
+
+      bool rate_control; 
+      double orig_src_ratio;
+      size_t driver_buffer_size;
    } audio_data;
 
    struct

settings.c

@@ -195,6 +195,8 @@ void config_set_defaults(void)
       strlcpy(g_settings.audio.device, audio_device, sizeof(g_settings.audio.device));
    g_settings.audio.latency = out_latency;
    g_settings.audio.sync = audio_sync;
+   g_settings.audio.rate_control = rate_control;
+   g_settings.audio.rate_control_delta = rate_control_delta;
 
    g_settings.rewind_enable = rewind_enable;
    g_settings.rewind_buffer_size = rewind_buffer_size;
@@ -429,6 +431,8 @@ bool config_load_file(const char *path)
    CONFIG_GET_STRING(audio.device, "audio_device");
    CONFIG_GET_INT(audio.latency, "audio_latency");
    CONFIG_GET_BOOL(audio.sync, "audio_sync");
+   CONFIG_GET_BOOL(audio.rate_control, "audio_rate_control");
+   CONFIG_GET_FLOAT(audio.rate_control_delta, "audio_rate_control_delta");
 
    CONFIG_GET_STRING(video.driver, "video_driver");
    CONFIG_GET_STRING(audio.driver, "audio_driver");

ssnes.c

@@ -246,6 +246,24 @@ void ssnes_render_cached_frame(void)
 #endif
 }
 
+static void readjust_audio_input_rate(void)
+{
+   int avail = driver.audio->write_avail(driver.audio_data);
+   //fprintf(stderr, "Audio buffer is %u%% full\n",
+   //      (unsigned)(100 - (avail * 100) / g_extern.audio_data.driver_buffer_size));
+
+   int half_size = g_extern.audio_data.driver_buffer_size / 2;
+   int delta_mid = avail - half_size;
+   double direction = (double)delta_mid / half_size;
+
+   double adjust = 1.0 + g_settings.audio.rate_control_delta * direction;
+
+   g_extern.audio_data.src_ratio = g_extern.audio_data.orig_src_ratio * adjust;
+
+   //fprintf(stderr, "New rate: %lf, Orig rate: %lf\n",
+   //      g_extern.audio_data.src_ratio, g_extern.audio_data.orig_src_ratio);
+}
+
 static bool audio_flush(const int16_t *data, size_t samples)
 {
 #ifdef HAVE_FFMPEG
@@ -284,6 +302,10 @@ static bool audio_flush(const int16_t *data, size_t samples)
       src_data.data_in = dsp_output.samples ? dsp_output.samples : g_extern.audio_data.data;
       src_data.data_out = g_extern.audio_data.outsamples;
       src_data.input_frames = dsp_output.samples ? dsp_output.frames : (samples / 2);
+
+      if (g_extern.audio_data.rate_control)
+         readjust_audio_input_rate();
+
       src_data.ratio = g_extern.audio_data.src_ratio;
 
       hermite_process(g_extern.audio_data.source, &src_data);

ssnes.cfg

@@ -146,6 +146,12 @@
 # Desired audio latency in milliseconds. Might not be honored if driver can't provide given latency.
 # audio_latency = 64
 
+# Enable experimental audio rate control.
+# audio_rate_control = false
+
+# Controls audio rate control delta. Defines how much input rate can be adjusted dynamically.
+# Input rate = in_rate * (1.0 +/- audio_rate_control_delta)
+# audio_rate_control_delta = 0.005
 
 #### Input