imdct15: rename to mdct15 and add a forward transform

Handles strides (needed for Opus transients), does pre-reindexing and folding
without needing a copy.

Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>

1 files changed, 67 insertions, 0 deletions

diff --git a/libavcodec/mdct15.h b/libavcodec/mdct15.h
new file mode 100644
index 0000000000..ef94edff6c
--- /dev/null
+++ b/libavcodec/mdct15.h
@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2017 Rostislav Pehlivanov <atomnuker@gmail.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVCODEC_MDCT15_H
+#define AVCODEC_MDCT15_H
+
+#include <stddef.h>
+
+#include "fft.h"
+
+typedef struct MDCT15Context {
+    int fft_n;
+    int len2;
+    int len4;
+    int inverse;
+    int *pfa_prereindex;
+    int *pfa_postreindex;
+
+    FFTContext ptwo_fft;
+
+    FFTComplex *tmp;
+
+    FFTComplex *twiddle_exptab;
+
+    /* 0 - 18: fft15 twiddles, 19 - 20: fft5 twiddles */
+    FFTComplex exptab[21];
+
+    /**
+     * Calculate a full 2N -> N MDCT
+     */
+    void (*mdct)(struct MDCT15Context *s, float *dst, const float *src, ptrdiff_t stride);
+
+    /**
+     * Calculate the middle half of the iMDCT
+     */
+    void (*imdct_half)(struct MDCT15Context *s, float *dst, const float *src,
+                       ptrdiff_t src_stride, float scale);
+} MDCT15Context;
+
+/**
+ * Init an (i)MDCT of the length 2 * 15 * (2^N)
+ */
+int ff_mdct15_init(MDCT15Context **ps, int inverse, int N, double scale);
+
+/**
+ * Frees a context
+ */
+void ff_mdct15_uninit(MDCT15Context **ps);
+
+#endif /* AVCODEC_MDCT15_H */