aboutsummaryrefslogtreecommitdiffstats
path: root/libavcodec/mdct.c
diff options
context:
space:
mode:
authorFabrice Bellard <fabrice@bellard.org>2002-10-28 00:34:08 +0000
committerFabrice Bellard <fabrice@bellard.org>2002-10-28 00:34:08 +0000
commitbb6f5690728486b71e280a295aef4c49d25ee758 (patch)
treebb4def001175ea9c928da56cc2eb8cbcc77488b1 /libavcodec/mdct.c
parent6d291820978ee1058f7154ed0b8cb7377c8bed51 (diff)
downloadffmpeg-bb6f5690728486b71e280a295aef4c49d25ee758.tar.gz
new generic FFT/MDCT code for audio codecs
Originally committed as revision 1088 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diffstat (limited to 'libavcodec/mdct.c')
-rw-r--r--libavcodec/mdct.c170
1 files changed, 170 insertions, 0 deletions
diff --git a/libavcodec/mdct.c b/libavcodec/mdct.c
new file mode 100644
index 0000000000..baab5d3152
--- /dev/null
+++ b/libavcodec/mdct.c
@@ -0,0 +1,170 @@
+/*
+ * MDCT/IMDCT transforms
+ * Copyright (c) 2002 Fabrice Bellard.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+#include "dsputil.h"
+
+/*
+ * init MDCT or IMDCT computation
+ */
+int mdct_init(MDCTContext *s, int nbits, int inverse)
+{
+ int n, n4, i;
+ float alpha;
+
+ memset(s, 0, sizeof(*s));
+ n = 1 << nbits;
+ s->nbits = nbits;
+ s->n = n;
+ n4 = n >> 2;
+ s->tcos = malloc(n4 * sizeof(FFTSample));
+ if (!s->tcos)
+ goto fail;
+ s->tsin = malloc(n4 * sizeof(FFTSample));
+ if (!s->tsin)
+ goto fail;
+
+ for(i=0;i<n4;i++) {
+ alpha = 2 * M_PI * (i + 1.0 / 8.0) / n;
+ s->tcos[i] = -cos(alpha);
+ s->tsin[i] = -sin(alpha);
+ }
+ if (fft_init(&s->fft, s->nbits - 2, inverse) < 0)
+ goto fail;
+ return 0;
+ fail:
+ av_freep(&s->tcos);
+ av_freep(&s->tsin);
+ return -1;
+}
+
+/* complex multiplication: p = a * b */
+#define CMUL(pre, pim, are, aim, bre, bim) \
+{\
+ float _are = (are);\
+ float _aim = (aim);\
+ float _bre = (bre);\
+ float _bim = (bim);\
+ (pre) = _are * _bre - _aim * _bim;\
+ (pim) = _are * _bim + _aim * _bre;\
+}
+
+/**
+ * Compute inverse MDCT of size N = 2^nbits
+ * @param output N samples
+ * @param input N/2 samples
+ * @param tmp N/2 samples
+ */
+void imdct_calc(MDCTContext *s, FFTSample *output,
+ const FFTSample *input, FFTSample *tmp)
+{
+ int k, n8, n4, n2, n, j;
+ const uint16_t *revtab = s->fft.revtab;
+ const FFTSample *tcos = s->tcos;
+ const FFTSample *tsin = s->tsin;
+ const FFTSample *in1, *in2;
+ FFTComplex *z = (FFTComplex *)tmp;
+
+ n = 1 << s->nbits;
+ n2 = n >> 1;
+ n4 = n >> 2;
+ n8 = n >> 3;
+
+ /* pre rotation */
+ in1 = input;
+ in2 = input + n2 - 1;
+ for(k = 0; k < n4; k++) {
+ j=revtab[k];
+ CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]);
+ in1 += 2;
+ in2 -= 2;
+ }
+ fft_calc(&s->fft, z);
+
+ /* post rotation + reordering */
+ /* XXX: optimize */
+ for(k = 0; k < n4; k++) {
+ CMUL(z[k].re, z[k].im, z[k].re, z[k].im, tcos[k], tsin[k]);
+ }
+ for(k = 0; k < n8; k++) {
+ output[2*k] = -z[n8 + k].im;
+ output[n2-1-2*k] = z[n8 + k].im;
+
+ output[2*k+1] = z[n8-1-k].re;
+ output[n2-1-2*k-1] = -z[n8-1-k].re;
+
+ output[n2 + 2*k]=-z[k+n8].re;
+ output[n-1- 2*k]=-z[k+n8].re;
+
+ output[n2 + 2*k+1]=z[n8-k-1].im;
+ output[n-2 - 2 * k] = z[n8-k-1].im;
+ }
+}
+
+/**
+ * Compute MDCT of size N = 2^nbits
+ * @param input N samples
+ * @param out N/2 samples
+ * @param tmp temporary storage of N/2 samples
+ */
+void mdct_calc(MDCTContext *s, FFTSample *out,
+ const FFTSample *input, FFTSample *tmp)
+{
+ int i, j, n, n8, n4, n2, n3;
+ FFTSample re, im, re1, im1;
+ const uint16_t *revtab = s->fft.revtab;
+ const FFTSample *tcos = s->tcos;
+ const FFTSample *tsin = s->tsin;
+ FFTComplex *x = (FFTComplex *)tmp;
+
+ n = 1 << s->nbits;
+ n2 = n >> 1;
+ n4 = n >> 2;
+ n8 = n >> 3;
+ n3 = 3 * n4;
+
+ /* pre rotation */
+ for(i=0;i<n8;i++) {
+ re = -input[2*i+3*n4] - input[n3-1-2*i];
+ im = -input[n4+2*i] + input[n4-1-2*i];
+ j = revtab[i];
+ CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]);
+
+ re = input[2*i] - input[n2-1-2*i];
+ im = -(input[n2+2*i] + input[n-1-2*i]);
+ j = revtab[n8 + i];
+ CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]);
+ }
+
+ fft_calc(&s->fft, x);
+
+ /* post rotation */
+ for(i=0;i<n4;i++) {
+ re = x[i].re;
+ im = x[i].im;
+ CMUL(re1, im1, re, im, -tsin[i], -tcos[i]);
+ out[2*i] = im1;
+ out[n2-1-2*i] = re1;
+ }
+}
+
+void mdct_end(MDCTContext *s)
+{
+ av_freep(&s->tcos);
+ av_freep(&s->tsin);
+ fft_end(&s->fft);
+}