add sound interpolation

2 files changed, 41 insertions, 1 deletions

diff --git a/libretro/libretro.c b/libretro/libretro.c
index c1665b4..b7aa69b 100644
--- a/libretro/libretro.c
+++ b/libretro/libretro.c
@@ -252,6 +252,8 @@ static void snes_init (void)
 	Settings.SpeedHacks = TRUE;
 
 	Settings.HBlankStart = (256 * Settings.H_Max) / SNES_HCOUNTER_MAX;
+
+   Settings.InterpolatedSound = TRUE;
    /*
    	Settings.SoundPlaybackRate = 5;
     Settings.Stereo = TRUE;
diff --git a/src/soundux.c b/src/soundux.c
index 60d5540..67f7127 100644
--- a/src/soundux.c
+++ b/src/soundux.c
@@ -187,6 +187,7 @@ void S9xFixSoundAfterSnapshotLoad()
       S9xSetSoundFrequency(i, SoundData.channels[i].hertz);

       SoundData.channels [i].envxx = SoundData.channels [i].envx << ENVX_SHIFT;

       SoundData.channels [i].next_sample = 0;

+      SoundData.channels [i].interpolate = 0;

       SoundData.channels [i].previous [0] = (int32) SoundData.channels [i].previous16 [0];

       SoundData.channels [i].previous [1] = (int32) SoundData.channels [i].previous16 [1];

    }

@@ -380,6 +381,11 @@ static void MixStereo(int sample_count)
             ch->sample_pointer = SOUND_DECODE_LENGTH - 1;

 

          ch->next_sample = ch->block[ch->sample_pointer];

+         ch->interpolate = 0;

+

+         if (Settings.InterpolatedSound && freq0 < FIXED_POINT && !mod)

+            ch->interpolate = ((ch->next_sample - ch->sample) *

+                               (long) freq0) / (long) FIXED_POINT;

       }

       VL = (ch->sample * ch-> left_vol_level) / 128;

       VR = (ch->sample * ch->right_vol_level) / 128;

@@ -587,17 +593,49 @@ static void MixStereo(int sample_count)
             else

                ch->next_sample = ch->block [ch->sample_pointer];

 

-            if (ch->type != SOUND_SAMPLE)

+            if (ch->type == SOUND_SAMPLE)

             {

+               if (Settings.InterpolatedSound && freq < FIXED_POINT && !mod)

+               {

+                  ch->interpolate = ((ch->next_sample - ch->sample) *

+                                     (long) freq) / (long) FIXED_POINT;

+                  ch->sample = (int16_t)(ch->sample + (((ch->next_sample - ch->sample) *

+                                                      (long)(ch->count)) / (long) FIXED_POINT));

+               }

+               else

+                  ch->interpolate = 0;

+            }

+            else

+            {

+#if 1

+               // Snes9x 1.53's SPC_DSP.cpp, by blargg

+               int feedback = (so.noise_gen << 13) ^ (so.noise_gen << 14);

+               so.noise_gen = (feedback & 0x4000) ^ (so.noise_gen >> 1);

+               ch->sample = (so.noise_gen << 17) >> 17;

+               ch->interpolate = 0;

+#else

                for (; VL > 0; VL--)

                   if ((so.noise_gen <<= 1) & 0x80000000L)

                      so.noise_gen ^= 0x0040001L;

                ch->sample = (so.noise_gen << 17) >> 17;

+#endif

             }

 

             VL = (ch->sample * ch-> left_vol_level) / 128;

             VR = (ch->sample * ch->right_vol_level) / 128;

          }

+         else

+         {

+            if (ch->interpolate)

+            {

+               int32_t s = (int32_t) ch->sample + ch->interpolate;

+

+               CLIP16(s);

+               ch->sample = (int16_t) s;

+               VL = (ch->sample * ch-> left_vol_level) / 128;

+               VR = (ch->sample * ch->right_vol_level) / 128;

+            }

+         }

 

          if (pitch_mod & (1 << (J + 1)))

             wave [I / 2] = ch->sample * ch->envx;