Some much needed organization

src/dsd_upsample.c

@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2010 DSD Author
+ * GPG Key ID: 0x3F1D7FD0 (74EF 430D F7F2 0A48 FCE6  F630 FAA2 635D 3F1D 7FD0)
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
+ * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
+ * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+ * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
+ * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+ * PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "dsd.h"
+
+void
+upsample (dsd_state * state, float invalue)
+{
+
+  int i, j, sum;
+  float *outbuf1, c, d;
+
+  outbuf1 = state->audio_out_float_buf_p;
+  outbuf1--;
+  c = *outbuf1;
+  d = invalue;
+  // basic triangle interpolation
+  outbuf1++;
+  *outbuf1 = ((invalue * (float) 0.166) + (c * (float) 0.834));
+  outbuf1++;
+  *outbuf1 = ((invalue * (float) 0.332) + (c * (float) 0.668));
+  outbuf1++;
+  *outbuf1 = ((invalue * (float) 0.5) + (c * (float) 0.5));
+  outbuf1++;
+  *outbuf1 = ((invalue * (float) 0.668) + (c * (float) 0.332));
+  outbuf1++;
+  *outbuf1 = ((invalue * (float) 0.834) + (c * (float) 0.166));
+  outbuf1++;
+  *outbuf1 = d;
+  outbuf1++;
+
+  if (state->audio_out_idx2 > 24)
+    {
+      // smoothing
+      outbuf1 -= 16;
+      for (j = 0; j < 4; j++)
+        {
+          for (i = 0; i < 6; i++)
+            {
+              sum = 0;
+              outbuf1 -= 2;
+              sum += (int)*outbuf1;
+              outbuf1 += 2;
+              sum += (int)*outbuf1;
+              outbuf1 += 2;
+              sum += (int)*outbuf1;
+              outbuf1 -= 2;
+              *outbuf1 = (sum / (float) 3);
+              outbuf1++;
+            }
+          outbuf1 -= 8;
+        }
+    }
+}