[FFmpeg-devel] [PATCH 2/4] lavc/fftw: add initial fftw wrapper
Ganesh Ajjanagadde
gajjanag at gmail.com
Fri Mar 25 01:50:50 CET 2016
No dct business yet; meant to be a minimal setup for now.
Such things added as FIXME's and TODO's.
Signed-off-by: Ganesh Ajjanagadde <gajjanag at gmail.com>
---
libavcodec/Makefile | 1 +
libavcodec/fftw.c | 68 +++++++++++++++++++++++++++++++++++++++++++++
libavcodec/fftw.h | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 149 insertions(+)
create mode 100644 libavcodec/fftw.c
create mode 100644 libavcodec/fftw.h
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index ef9eb98..5b35d89 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -63,6 +63,7 @@ FFT-OBJS-$(CONFIG_HARDCODED_TABLES) += cos_tables.o cos_fixed_tables.o
OBJS-$(CONFIG_FFT) += avfft.o fft_fixed.o fft_float.o \
fft_fixed_32.o fft_init_table.o \
$(FFT-OBJS-yes)
+OBJS-$(CONFIG_LIBFFTW3) += fftw.o
OBJS-$(CONFIG_FLACDSP) += flacdsp.o
OBJS-$(CONFIG_FMTCONVERT) += fmtconvert.o
OBJS-$(CONFIG_GOLOMB) += golomb.o
diff --git a/libavcodec/fftw.c b/libavcodec/fftw.c
new file mode 100644
index 0000000..d3c2e1f
--- /dev/null
+++ b/libavcodec/fftw.c
@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2003, 2007-11 Matteo Frigo
+ * Copyright (c) 2003, 2007-11 Massachusetts Institute of Technology.
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU 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.
+ */
+
+#include "libavutil/mem.h"
+#include "fftw.h"
+
+static void fft_calc(struct FFTWContext *s, FFTWComplex *z)
+{
+ fftwf_execute_dft(s->plan, z, z);
+}
+
+av_cold int ff_fftw_init(FFTWContext *s, int n, int inverse)
+{
+ FFTWComplex *tmp;
+ s->n = n;
+ s->inverse = inverse;
+ s->fft_calc = fft_calc;
+ // create a temporary array for computing the plan
+ // note: there is no real advantage to doing this on the first calc run;
+ // plan creation is not guaranteed to not touch the array at hand.
+ tmp = av_malloc(sizeof(*tmp) * n);
+ if (!tmp)
+ goto fail;
+ else {
+ /* FIXME: plan creation is not threadsafe */
+ /* TODO: some time generate "wisdom" files offline for common arches
+ and fft sizes, dump them in a folder, w/o compression as the one time
+ plan init can get expensive for long FFT's (seconds for len ~ 8192). */
+ if (inverse)
+ s->plan = fftwf_plan_dft_1d(n, tmp, tmp, FFTW_BACKWARD, FFTW_PATIENT);
+ else
+ s->plan = fftwf_plan_dft_1d(n, tmp, tmp, FFTW_FORWARD, FFTW_PATIENT);
+ /* apparently never happens in default fftw configurations; just being safe */
+ if (!s->plan)
+ goto fail;
+ }
+ av_free(tmp);
+ return 0;
+fail:
+ av_freep(&tmp);
+ return AVERROR(ENOMEM);
+}
+
+av_cold void ff_fftw_deinit(FFTWContext *s)
+{
+ fftwf_destroy_plan(s->plan);
+ // TODO: doing this complete cleanup may not be ideal; it will bring FFTW
+ // to a clean slate and thus future init's won't benefit from some of the
+ // accumulated plan knowledge/"wisdom".
+ fftwf_cleanup();
+}
diff --git a/libavcodec/fftw.h b/libavcodec/fftw.h
new file mode 100644
index 0000000..656e5db
--- /dev/null
+++ b/libavcodec/fftw.h
@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 2003, 2007-11 Matteo Frigo
+ * Copyright (c) 2003, 2007-11 Massachusetts Institute of Technology.
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU 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_FFTW_H
+#define AVCODEC_FFTW_H
+
+/**
+ * @file
+ * @ingroup libavc
+ * FFTW based FFT functions header
+ */
+
+#include <fftw3.h>
+
+typedef fftwf_complex FFTWComplex;
+typedef fftwf_plan FFTWPlan;
+
+typedef struct FFTWContext {
+ /**
+ * Length of the FFT. Note that the length need not be a power of 2; powers
+ * of 2 are most efficient though.
+ */
+ int n;
+ /**
+ * if 0 perform forward transform, if 1 perform reverse transform.
+ */
+ int inverse;
+ /**
+ * An opaque internal pointer containing plan information, essentially target
+ * optimization information for the specified FFT parameters such as n.
+ * NOTE: If one calls fft_calc on the exact same array repeatedly, or on the
+ * same length with proper alignment, and with the same flags, there is no
+ * issue. However, if these conditions are not met, it is necessary to
+ * recompute plans. Note that this is often cheap. For precise information on
+ * this, see the fftw docs: http://www.fftw.org/fftw3.pdf, or
+ * http://www.fftw.org/faq/section3.html#planperarray.
+ */
+ FFTWPlan plan;
+ /**
+ * Do a complex, in-place FFT with the parameters defined in ff_fftw_init().
+ * No 1.0/sqrt(n) normalization is done.
+ */
+ void (*fft_calc)(struct FFTWContext *s, FFTWComplex *z);
+ /* TODO: add dct, rdft, etc */
+} FFTWContext;
+
+/**
+ * Set up a complex, in-place FFT.
+ * @param s pointer to an FFTWContext
+ * @param n length of the input array
+ * @param inverse if 0 perform the forward transform, if 1 perform the inverse
+ * @return 0 on success, negative AVERROR code otherwise
+ */
+int ff_fftw_init(FFTWContext *s, int n, int inverse);
+
+/**
+ * Clean up an FFTWContext.
+ * @param s pointer to an FFTWContext
+ */
+void ff_fftw_deinit(FFTWContext *s);
+
+
+#endif /* AVCODEC_FFTW_H */
--
2.7.4
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