Index: src/aubio.h
===================================================================
--- src/aubio.h	(revision 9fa0ed1c5637f2225d54d517df5bacd18f7b9564)
+++ src/aubio.h	(revision 60583a3817b8c4120861ec7df2e9836146efd54d)
@@ -183,4 +183,5 @@
 #include "temporal/c_weighting.h"
 #include "spectral/fft.h"
+#include "spectral/dct.h"
 #include "spectral/phasevoc.h"
 #include "spectral/filterbank.h"
Index: src/spectral/dct.h
===================================================================
--- src/spectral/dct.h	(revision 60583a3817b8c4120861ec7df2e9836146efd54d)
+++ src/spectral/dct.h	(revision 60583a3817b8c4120861ec7df2e9836146efd54d)
@@ -0,0 +1,85 @@
+/*
+  Copyright (C) 2017 Paul Brossier <piem@aubio.org>
+
+  This file is part of aubio.
+
+  aubio is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  aubio is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with aubio.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+/** \file
+
+  Discrete Cosine Transform
+
+  Functions aubio_dct_do() and aubio_dct_rdo() are equivalent to MATLAB/Octave
+  dct() and idct() functions, as well as scipy.fftpack.dct(x, norm='ortho') and
+  scipy.fftpack.idct(x, norm='ortho')
+
+  \example spectral/test-dct.c
+
+*/
+
+#ifndef AUBIO_DCT_H
+#define AUBIO_DCT_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** DCT object
+
+  This object computes forward and backward DCT type 2 with orthonormal
+  scaling.
+
+*/
+typedef struct _aubio_dct_t aubio_dct_t;
+
+/** create new DCT computation object
+
+  \param size length of the DCT
+
+*/
+aubio_dct_t * new_aubio_dct(uint_t size);
+
+/** compute forward DCT
+
+  \param s dct object as returned by new_aubio_dct
+  \param input input signal
+  \param output transformed input array
+
+*/
+void aubio_dct_do (aubio_dct_t *s, const fvec_t * input, fvec_t * output);
+
+/** compute backward DCT
+
+  \param s dct object as returned by new_aubio_dct
+  \param input input signal
+  \param output transformed input array
+
+*/
+void aubio_dct_rdo (aubio_dct_t *s, const fvec_t * input, fvec_t * output);
+
+
+/** delete DCT object
+
+  \param s dct object as returned by new_aubio_dct
+
+*/
+void del_aubio_dct (aubio_dct_t *s);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* AUBIO_DCT_H */
Index: src/spectral/dct_ooura.c
===================================================================
--- src/spectral/dct_ooura.c	(revision 60583a3817b8c4120861ec7df2e9836146efd54d)
+++ src/spectral/dct_ooura.c	(revision 60583a3817b8c4120861ec7df2e9836146efd54d)
@@ -0,0 +1,85 @@
+/*
+  Copyright (C) 2017 Paul Brossier <piem@aubio.org>
+
+  This file is part of aubio.
+
+  aubio is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  aubio is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with aubio.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+#include "aubio_priv.h"
+#include "fvec.h"
+#include "cvec.h"
+#include "spectral/dct.h"
+
+extern void aubio_ooura_ddct(int, int, smpl_t *, int *, smpl_t *);
+
+struct _aubio_dct_t {
+  uint_t size;
+  fvec_t *input;
+  smpl_t *w;
+  int *ip;
+};
+
+aubio_dct_t * new_aubio_dct (uint_t size) {
+  aubio_dct_t * s = AUBIO_NEW(aubio_dct_t);
+  if (aubio_is_power_of_two(size) != 1) {
+    AUBIO_ERR("dct: can only create with sizes power of two, requested %d\n",
+        size);
+    goto beach;
+  }
+  s->size = size;
+  s->input = new_fvec(s->size);
+  s->w = AUBIO_ARRAY(smpl_t, s->size * 5 / 4);
+  s->ip = AUBIO_ARRAY(int, 3 + (1 << (int)FLOOR(LOG(s->size/2) / LOG(2))) / 2);
+  s->ip[0] = 0;
+  return s;
+beach:
+  AUBIO_FREE(s);
+  return NULL;
+}
+
+void del_aubio_dct(aubio_dct_t *s) {
+  del_fvec(s->input);
+  AUBIO_FREE(s->ip);
+  AUBIO_FREE(s->w);
+  AUBIO_FREE(s);
+}
+
+void aubio_dct_do(aubio_dct_t *s, const fvec_t *input, fvec_t *output) {
+  uint_t i = 0;
+  fvec_copy(input, s->input);
+  aubio_ooura_ddct(s->size, -1, s->input->data, s->ip, s->w);
+  // apply orthonormal scaling
+  s->input->data[0] *= 2.* SQRT(1./(4.*s->input->length));
+  for (i = 1; i < s->input->length; i++) {
+    s->input->data[i] *= 2. * SQRT(1./(2.*s->input->length));
+  }
+  fvec_copy(s->input, output);
+}
+
+void aubio_dct_rdo(aubio_dct_t *s, const fvec_t *input, fvec_t *output) {
+  uint_t i = 0;
+  fvec_copy(input, s->input);
+  s->input->data[0] /= 2.* SQRT(1./(4.*s->input->length));
+  for (i = 1; i < s->input->length; i++) {
+    s->input->data[i] /= 2. * SQRT(1./(2.*s->input->length));
+  }
+  s->input->data[0] *= .5;
+  aubio_ooura_ddct(s->size, 1, s->input->data, s->ip, s->w);
+  for (i = 0; i < s->input->length; i++) {
+    s->input->data[i] *= 2./s->input->length;
+  }
+  fvec_copy(s->input, output);
+}
