lowercasing filenames, part3

[picodrive.git] / pico / pico / xpcm.c

diff --git a/pico/pico/xpcm.c b/pico/pico/xpcm.c
new file mode 100644 (file)
index 0000000..da3f480
--- /dev/null
+++ b/pico/pico/xpcm.c
@@ -0,0 +1,114 @@
+/*
+ * The following ADPCM algorithm was stolen from MAME aica driver.
+ * I'm quite sure it's not the right one, but it's the
+ * best sounding of the ones that I tried.
+ */
+
+#include "../pico_int.h"
+
+#define ADPCMSHIFT      8
+#define ADFIX(f)        (int) ((double)f * (double)(1<<ADPCMSHIFT))
+
+/* limitter */
+#define Limit(val, max, min) { \
+       if ( val > max )      val = max; \
+       else if ( val < min ) val = min; \
+}
+
+static const int TableQuant[8] =
+{
+  ADFIX(0.8984375),
+  ADFIX(0.8984375),
+  ADFIX(0.8984375),
+  ADFIX(0.8984375),
+  ADFIX(1.19921875),
+  ADFIX(1.59765625),
+  ADFIX(2.0),
+  ADFIX(2.3984375)
+};
+
+// changed using trial and error..
+//static const int quant_mul[16] = { 1, 3, 5, 7, 9, 11, 13, 15, -1, -3, -5, -7, -9, -11, -13, -15 };
+static const int quant_mul[16]   = { 1, 3, 5, 7, 9, 11, 13, -1, -1, -3, -5, -7, -9, -11, -13, -15 };
+
+static int sample = 0, quant = 0, sgn = 0;
+static int stepsamples = (44100<<10)/16000;
+
+
+PICO_INTERNAL void PicoPicoPCMReset(void)
+{
+  sample = sgn = 0;
+  quant = 0x7f;
+  memset(PicoPicohw.xpcm_buffer, 0, sizeof(PicoPicohw.xpcm_buffer));
+}
+
+PICO_INTERNAL void PicoPicoPCMRerate(int xpcm_rate)
+{
+  stepsamples = (PsndRate<<10)/xpcm_rate;
+}
+
+#define XSHIFT 6
+
+#define do_sample() \
+{ \
+  int delta = quant * quant_mul[srcval] >> XSHIFT; \
+  sample += delta - (delta >> 2); /* 3/4 */ \
+  quant = (quant * TableQuant[srcval&7]) >> ADPCMSHIFT; \
+  Limit(quant, 0x6000, 0x7f); \
+  Limit(sample, 32767*3/4, -32768*3/4); \
+}
+
+PICO_INTERNAL void PicoPicoPCMUpdate(short *buffer, int length, int stereo)
+{
+  unsigned char *src = PicoPicohw.xpcm_buffer;
+  unsigned char *lim = PicoPicohw.xpcm_ptr;
+  int srcval, needsamples = 0;
+
+  if (src == lim) goto end;
+
+  for (; length > 0 && src < lim; src++)
+  {
+    srcval = *src >> 4;
+    do_sample();
+
+    for (needsamples += stepsamples; needsamples > (1<<10) && length > 0; needsamples -= (1<<10), length--) {
+      *buffer++ += sample;
+      if (stereo) { buffer[0] = buffer[-1]; buffer++; }
+    }
+
+    srcval = *src & 0xf;
+    do_sample();
+
+    for (needsamples += stepsamples; needsamples > (1<<10) && length > 0; needsamples -= (1<<10), length--) {
+      *buffer++ += sample;
+      if (stereo) { buffer[0] = buffer[-1]; buffer++; }
+    }
+
+    // lame normalization stuff, needed due to wrong adpcm algo
+    sgn += (sample < 0) ? -1 : 1;
+    if (sgn < -16 || sgn > 16) sample -= sample >> 5;
+  }
+
+  if (src < lim) {
+    int di = lim - src;
+    memmove(PicoPicohw.xpcm_buffer, src, di);
+    PicoPicohw.xpcm_ptr = PicoPicohw.xpcm_buffer + di;
+    elprintf(EL_PICOHW, "xpcm update: over %i", di);
+    // adjust fifo
+    PicoPicohw.fifo_bytes = di;
+    return;
+  }
+
+  elprintf(EL_PICOHW, "xpcm update: under %i", length);
+  PicoPicohw.xpcm_ptr = PicoPicohw.xpcm_buffer;
+
+end:
+  if (stereo)
+    // still must expand SN76496 to stereo
+    for (; length > 0; buffer+=2, length--)
+      buffer[1] = buffer[0];
+
+  sample = sgn = 0;
+  quant = 0x7f;
+}
+