Changeset 116bd1b

Timestamp:

Feb 16, 2016, 5:47:43 PM (8 years ago)

Author:

Paul Brossier <piem@piem.org>

Branches:

feature/autosink, feature/cnn, feature/cnn_org, feature/constantq, feature/crepe, feature/crepe_org, feature/pitchshift, feature/pydocstrings, feature/timestretch, fix/ffmpeg5, master, pitchshift, sampler, timestretch, yinfft+

Children:

7cdabbe

Parents:

d21a4b1

Message:

src/mathutils.h: add fvec_ishift

Location:

src

Files:

• mathutils.c (modified) (1 diff)
• mathutils.h (modified) (1 diff)

src/mathutils.c

@@ -254 +254 @@
 fvec_shift (fvec_t * s)
 {
+  uint_t half = s->length / 2, start = half;
+  // if length is odd, middle element is moved to the end
+  if (2 * half < s->length) start ++;
 #ifndef HAVE_ATLAS
-  uint_t j;
-  for (j = 0; j < s->length / 2; j++) {
-    ELEM_SWAP (s->data[j], s->data[j + s->length / 2]);
-  }
-#else
-  uint_t half = s->length / 2;
-  aubio_cblas_swap(half, s->data, 1, s->data + half, 1);
-#endif
+  for (uint_t j = 0; j < half; j++) {
+    ELEM_SWAP (s->data[j], s->data[j + start]);
+  }
+#else
+  aubio_cblas_swap(half, s->data, 1, s->data + start, 1);
+#endif
+  if (start != half) {
+    for (uint_t j = 0; j < half; j++) {
+      ELEM_SWAP (s->data[j + start - 1], s->data[j + start]);
+    }
+  }
+}
+
+void
+fvec_ishift (fvec_t * s)
+{
+  uint_t half = s->length / 2, start = half;
+  // if length is odd, middle element is moved to the beginning
+  if (2 * half < s->length) start ++;
+#ifndef HAVE_ATLAS
+  for (uint_t j = 0; j < half; j++) {
+    ELEM_SWAP (s->data[j], s->data[j + start]);
+  }
+#else
+  aubio_cblas_swap(half, s->data, 1, s->data + start, 1);
+#endif
+  if (start != half) {
+    for (uint_t j = 0; j < half; j++) {
+      ELEM_SWAP (s->data[half], s->data[j]);
+    }
+  }
 }
 

src/mathutils.h

@@ -99 +99 @@
 */
 void fvec_shift (fvec_t * v);
+
+/** swap the left and right halves of a vector
+
+  This function swaps the left part of the signal with the right part of the
+signal. Therefore
+
+  \f$ a[0], a[1], ..., a[\frac{N}{2}], a[\frac{N}{2}+1], ..., a[N-1], a[N] \f$
+
+  becomes
+
+  \f$ a[\frac{N}{2}+1], ..., a[N-1], a[N], a[0], a[1], ..., a[\frac{N}{2}] \f$
+
+  This operation, known as 'ifftshift' in the Matlab Signal Processing Toolbox,
+can be used after computing the inverse FFT to simplify the phase relationship
+of the resulting spectrum. See Amalia de Götzen's paper referred to above.
+
+*/
+void fvec_ishift (fvec_t * v);
 
 /** compute the sum of all elements of a vector