1 /* Copyright (c) 2007-2008 CSIRO 2 Copyright (c) 2007-2008 Xiph.Org Foundation 3 Written by Jean-Marc Valin */ 4 /* 5 Redistribution and use in source and binary forms, with or without 6 modification, are permitted provided that the following conditions 7 are met: 8 9 - Redistributions of source code must retain the above copyright 10 notice, this list of conditions and the following disclaimer. 11 12 - Redistributions in binary form must reproduce the above copyright 13 notice, this list of conditions and the following disclaimer in the 14 documentation and/or other materials provided with the distribution. 15 16 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER 20 OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 21 EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 22 PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 23 PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 24 LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 25 NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 26 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 /* This is a simple MDCT implementation that uses a N/4 complex FFT 30 to do most of the work. It should be relatively straightforward to 31 plug in pretty much and FFT here. 32 33 This replaces the Vorbis FFT (and uses the exact same API), which 34 was a bit too messy and that was ending up duplicating code 35 (might as well use the same FFT everywhere). 36 37 The algorithm is similar to (and inspired from) Fabrice Bellard's 38 MDCT implementation in FFMPEG, but has differences in signs, ordering 39 and scaling in many places. 40 */ 41 42 #ifndef MDCT_H 43 #define MDCT_H 44 45 #include "opus_defines.h" 46 #include "kiss_fft.h" 47 #include "arch.h" 48 49 typedef struct { 50 int n; 51 int maxshift; 52 const kiss_fft_state *kfft[4]; 53 const kiss_twiddle_scalar * OPUS_RESTRICT trig; 54 } mdct_lookup; 55 56 int clt_mdct_init(mdct_lookup *l,int N, int maxshift); 57 void clt_mdct_clear(mdct_lookup *l); 58 59 /** Compute a forward MDCT and scale by 4/N, trashes the input array */ 60 void clt_mdct_forward(const mdct_lookup *l, kiss_fft_scalar *in, 61 kiss_fft_scalar * OPUS_RESTRICT out, 62 const opus_val16 *window, int overlap, int shift, int stride); 63 64 /** Compute a backward MDCT (no scaling) and performs weighted overlap-add 65 (scales implicitly by 1/2) */ 66 void clt_mdct_backward(const mdct_lookup *l, kiss_fft_scalar *in, 67 kiss_fft_scalar * OPUS_RESTRICT out, 68 const opus_val16 * OPUS_RESTRICT window, int overlap, int shift, int stride); 69 70 #endif 71