opus/celt/mdct.h

/* Copyright (c) 2007-2012 IETF Trust, CSIRO, Xiph.Org Foundation. All rights reserved.
   Written by Jean-Marc Valin */
/*

   This file is extracted from RFC6716. Please see that RFC for additional
   information.

   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.

   - Neither the name of Internet Society, IETF or IETF Trust, nor the
   names of specific contributors, may be used to endorse or promote
   products derived from this software without specific prior written
   permission.

   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 COPYRIGHT OWNER
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*/

/* 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