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authorJean-Marc Valin <jmvalin@jmvalin.ca>2011-09-13 18:21:18 -0700
committerJean-Marc Valin <jmvalin@jmvalin.ca>2011-09-13 18:21:18 -0700
commitc37499090b68e03cbd102afa2ac79f6db7c39247 (patch)
tree84fcb16201cbddda4241386183beb8a43342435f /celt/mdct.h
parent92675068a425677855c0a379efc4f10e51ee9595 (diff)
downloadopus-c37499090b68e03cbd102afa2ac79f6db7c39247.tar.gz
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+/* Copyright (c) 2007-2008 CSIRO
+ Copyright (c) 2007-2008 Xiph.Org Foundation
+ Written by Jean-Marc Valin */
+/*
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions
+ are met:
+
+ - Redistributions of source code must retain the above copyright
+ notice, this list of conditions and the following disclaimer.
+
+ - Redistributions in binary form must reproduce the above copyright
+ notice, this list of conditions and the following disclaimer in the
+ documentation and/or other materials provided with the distribution.
+
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR
+ CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+/* This is a simple MDCT implementation that uses a N/4 complex FFT
+ to do most of the work. It should be relatively straightforward to
+ plug in pretty much and FFT here.
+
+ This replaces the Vorbis FFT (and uses the exact same API), which
+ was a bit too messy and that was ending up duplicating code
+ (might as well use the same FFT everywhere).
+
+ The algorithm is similar to (and inspired from) Fabrice Bellard's
+ MDCT implementation in FFMPEG, but has differences in signs, ordering
+ and scaling in many places.
+*/
+
+#ifndef MDCT_H
+#define MDCT_H
+
+#include "kiss_fft.h"
+#include "arch.h"
+
+typedef struct {
+ int n;
+ int maxshift;
+ const kiss_fft_state *kfft[4];
+ const kiss_twiddle_scalar * restrict trig;
+} mdct_lookup;
+
+int clt_mdct_init(mdct_lookup *l,int N, int maxshift);
+void clt_mdct_clear(mdct_lookup *l);
+
+/** Compute a forward MDCT and scale by 4/N, trashes the input array */
+void clt_mdct_forward(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scalar *out,
+ const opus_val16 *window, int overlap, int shift, int stride);
+
+/** Compute a backward MDCT (no scaling) and performs weighted overlap-add
+ (scales implicitly by 1/2) */
+void clt_mdct_backward(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scalar *out,
+ const opus_val16 * restrict window, int overlap, int shift, int stride);
+
+#endif