[FFmpeg-devel] [PATCH] avfilter: add nonlinearstretch filter.
Mathias Rasmussen
mathiasvr at gmail.com
Mon Jun 22 01:47:30 EEST 2020
---
Hi there! First time contributor here.
I've made a filter for performing nonlinear stretching of videos,
also known as dynamic stretch and similar to GoPro's SuperView.
I left some questions as TODO's in the code that I hope you can help me answer.
Also, how do you run the test or see the output? I seem to just get empty files.
This is also my first time using git through a mailing list
so please let me know if I'm doing something wierd. Thanks! :)
Changelog | 1 +
doc/filters.texi | 34 ++++
libavfilter/Makefile | 1 +
libavfilter/allfilters.c | 1 +
libavfilter/version.h | 2 +-
libavfilter/vf_nonlinearstretch.c | 268 ++++++++++++++++++++++++++++++
tests/fate/filter-video.mak | 3 +
7 files changed, 309 insertions(+), 1 deletion(-)
create mode 100644 libavfilter/vf_nonlinearstretch.c
diff --git a/Changelog b/Changelog
index a60e7d2eb8..d6f0b0ac74 100644
--- a/Changelog
+++ b/Changelog
@@ -2,6 +2,7 @@ Entries are sorted chronologically from oldest to youngest within each release,
releases are sorted from youngest to oldest.
version <next>:
+- Nonlinear stretch filter
- AudioToolbox output device
- MacCaption demuxer
diff --git a/doc/filters.texi b/doc/filters.texi
index 551604a143..5657814c13 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -13989,6 +13989,40 @@ Add temporal and uniform noise to input video:
noise=alls=20:allf=t+u
@end example
+ at section nonlinearstretch
+
+Nonlinear stretch video input frame.
+
+The filter stretches the input horizonatally to a given target width by gradually increasing
+the stretching amount from the middle towards the sides.
+
+Commonly used to stretch videos from 4:3 to 16:9 aspect ratio.
+
+The filter accepts the following options:
+
+ at table @option
+ at item width
+Set output width.
+ at item a
+Set stretch factor exponent. Defaults to @code{2.0}.
+A larger value retains more of the original proportions around center, while increasing stretching along the sides.
+A value of 1.0 relaxes the filter to a linear stretch.
+ at item interpolate
+Enable/disable linear interpolation. Enabled by default.
+ at end table
+
+ at subsection Examples
+
+Stretch input width to 2560 with less stretching around the middle of the frame.
+ at example
+nonlinearstretch=width=2560:a=2.5
+ at end example
+
+Stretch input width to 1920 with default stretch factor and no interpolation.
+ at example
+nonlinearstretch=width=1920:interpolate=0
+ at end example
+
@section normalize
Normalize RGB video (aka histogram stretching, contrast stretching).
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 5123540653..469c4ca66f 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -321,6 +321,7 @@ OBJS-$(CONFIG_NLMEANS_OPENCL_FILTER) += vf_nlmeans_opencl.o opencl.o ope
OBJS-$(CONFIG_NNEDI_FILTER) += vf_nnedi.o
OBJS-$(CONFIG_NOFORMAT_FILTER) += vf_format.o
OBJS-$(CONFIG_NOISE_FILTER) += vf_noise.o
+OBJS-$(CONFIG_NONLINEARSTRETCH_FILTER) += vf_nonlinearstretch.o
OBJS-$(CONFIG_NORMALIZE_FILTER) += vf_normalize.o
OBJS-$(CONFIG_NULL_FILTER) += vf_null.o
OBJS-$(CONFIG_OCR_FILTER) += vf_ocr.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 1183e40267..d7be2a2ca2 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -306,6 +306,7 @@ extern AVFilter ff_vf_nlmeans_opencl;
extern AVFilter ff_vf_nnedi;
extern AVFilter ff_vf_noformat;
extern AVFilter ff_vf_noise;
+extern AVFilter ff_vf_nonlinearstretch;
extern AVFilter ff_vf_normalize;
extern AVFilter ff_vf_null;
extern AVFilter ff_vf_ocr;
diff --git a/libavfilter/version.h b/libavfilter/version.h
index 37015085fa..308fbe07c3 100644
--- a/libavfilter/version.h
+++ b/libavfilter/version.h
@@ -30,7 +30,7 @@
#include "libavutil/version.h"
#define LIBAVFILTER_VERSION_MAJOR 7
-#define LIBAVFILTER_VERSION_MINOR 86
+#define LIBAVFILTER_VERSION_MINOR 87
#define LIBAVFILTER_VERSION_MICRO 100
diff --git a/libavfilter/vf_nonlinearstretch.c b/libavfilter/vf_nonlinearstretch.c
new file mode 100644
index 0000000000..f6c7f46bc6
--- /dev/null
+++ b/libavfilter/vf_nonlinearstretch.c
@@ -0,0 +1,268 @@
+/*
+ * Copyright (c) 2020 Mathias V. Rasmussen
+ *
+ * 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
+ */
+
+/**
+ * @file
+ * Nonlinear stretch filter
+ */
+
+#include "libavutil/pixdesc.h"
+#include "libavutil/opt.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+#include "math.h"
+
+typedef struct NonlinearStretchContext {
+ const AVClass *class;
+ int target_width;
+ double exp;
+ int interpolate;
+
+ int nb_planes;
+ int plane_width[2];
+ int plane_height[2];
+ double *plane_xmap[2];
+} NonlinearStretchContext;
+
+typedef struct ThreadData {
+ AVFrame *in, *out;
+} ThreadData;
+
+#define OFFSET(x) offsetof(NonlinearStretchContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption nonlinearstretch_options[] = {
+ { "width", "set target width", OFFSET(target_width), AV_OPT_TYPE_INT, {.i64=0}, 0, UINT16_MAX, FLAGS },
+ { "a", "set exponential stretch factor", OFFSET(exp), AV_OPT_TYPE_DOUBLE, {.dbl=2.}, 1, 50, FLAGS },
+ { "interpolate", "perform linear interpolation", OFFSET(interpolate), AV_OPT_TYPE_BOOL, {.i64=1}, 0, 1, FLAGS },
+ { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(nonlinearstretch);
+
+static int query_formats(AVFilterContext *ctx)
+{
+ // TODO: which formats are supported when using `av_pix_fmt_count_planes()` and vsub/hsub?
+ // Is there a way to know the number of planes used? E.g. is it always at most 3?
+ // Lastly, is it necessary to support RGB style formats? I assume ffmpeg is doing some form of conversion if not?
+ static const enum AVPixelFormat pix_fmts[] = {
+ AV_PIX_FMT_GBRP, AV_PIX_FMT_GBRAP,
+ // AV_PIX_FMT_ARGB, AV_PIX_FMT_RGBA,
+ // AV_PIX_FMT_ABGR, AV_PIX_FMT_BGRA,
+ // AV_PIX_FMT_0RGB, AV_PIX_FMT_RGB0,
+ // AV_PIX_FMT_0BGR, AV_PIX_FMT_BGR0,
+ // AV_PIX_FMT_RGB24, AV_PIX_FMT_BGR24,
+ AV_PIX_FMT_GRAY8,
+ AV_PIX_FMT_YUV410P,
+ AV_PIX_FMT_YUV444P, AV_PIX_FMT_YUVJ444P,
+ AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUVJ420P,
+ AV_PIX_FMT_YUVA444P, AV_PIX_FMT_YUVA420P,
+ AV_PIX_FMT_YUV420P10LE, AV_PIX_FMT_YUVA420P10LE,
+ AV_PIX_FMT_YUV444P10LE, AV_PIX_FMT_YUVA444P10LE,
+ AV_PIX_FMT_YUV420P12LE,
+ AV_PIX_FMT_YUV444P12LE,
+ AV_PIX_FMT_YUV444P16LE, AV_PIX_FMT_YUVA444P16LE,
+ AV_PIX_FMT_YUV420P16LE, AV_PIX_FMT_YUVA420P16LE,
+ AV_PIX_FMT_YUV444P9LE, AV_PIX_FMT_YUVA444P9LE,
+ AV_PIX_FMT_YUV420P9LE, AV_PIX_FMT_YUVA420P9LE,
+ AV_PIX_FMT_NONE
+ };
+
+ AVFilterFormats *fmts_list = ff_make_format_list(pix_fmts);
+ if (!fmts_list)
+ return AVERROR(ENOMEM);
+ return ff_set_common_formats(ctx, fmts_list);
+}
+
+// non-linear mapping of target frame pixel
+// x-coordinate to position in the source frame.
+#define SIGN(x) (x < 0 ? -1 : 1)
+static double stretch_x(int target_x, int target_width, int src_width, double exp)
+{
+ double x = 2.0 * target_x / target_width - 1;
+
+ double step = 0.5 + 0.5 * pow(fabs(x), exp) * SIGN(x);
+
+ double src_x = target_x - step * (target_width - src_width);
+
+ // large exponent and high stretch ratio
+ // can cause over- and underflow of the frame width
+ return av_clipd(src_x, 0, src_width - 1);
+}
+
+static int config_props(AVFilterLink *outlink)
+{
+ AVFilterContext *ctx = outlink->src;
+ NonlinearStretchContext *s = ctx->priv;
+ AVFilterLink *inlink = ctx->inputs[0];
+ int i, pt;
+ int plane_width_in[2];
+
+ const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
+ const uint8_t hsub = desc->log2_chroma_w;
+ const uint8_t vsub = desc->log2_chroma_h;
+
+ // TODO: is it better to make the width option required? Instead of computing default.
+ outlink->w = s->target_width ? s->target_width : inlink->h * 16 / 9;
+ outlink->h = inlink->h;
+
+ s->nb_planes = av_pix_fmt_count_planes(inlink->format);
+
+ // initialize values for different plane types
+ s->plane_height[0] = outlink->h;
+ s->plane_width[0] = outlink->w;
+ plane_width_in[0] = inlink->w;
+ s->plane_height[1] = AV_CEIL_RSHIFT(outlink->h, vsub);
+ s->plane_width[1] = AV_CEIL_RSHIFT(outlink->w, hsub);
+ plane_width_in[1] = AV_CEIL_RSHIFT(inlink->w, hsub);
+
+ for (pt = 0; pt < 2; pt++) {
+ s->plane_xmap[pt] = av_malloc_array(s->plane_width[pt], sizeof(*s->plane_xmap[pt]));
+
+ if (!s->plane_xmap[pt])
+ return AVERROR(ENOMEM);
+
+ // precompute mapping between input and output pixels on the x-axis
+ for (i = 0; i < s->plane_width[pt]; i++) {
+ double src_x = stretch_x(i, s->plane_width[pt], plane_width_in[pt], s->exp);
+ s->plane_xmap[pt][i] = src_x;
+ }
+ }
+
+ return 0;
+}
+
+// TODO: Should this be as is, inlined or defined
+static double lerp(double v0, double v1, double t)
+{
+ return v0 + t * (v1 - v0);
+}
+
+// TODO: Should this inlined?
+static inline void stretch_frame(int width, int height,
+ uint8_t *dst, int dst_linesize,
+ const uint8_t *src, int src_linesize,
+ double *xmap, int interpolate)
+{
+ int i, x;
+ for (i = 0; i < height; i++) {
+ for (x = 0; x < width; x++) {
+ int px1 = floor(xmap[x]);
+ int px2 = ceil(xmap[x]);
+ dst[x] = interpolate
+ ? lerp(src[px1], src[px2], xmap[x] - px1)
+ : src[px1];
+ }
+ dst += dst_linesize;
+ src += src_linesize;
+ }
+}
+
+static int filter_slice(AVFilterContext *ctx, void *arg, int job, int nb_jobs)
+{
+ NonlinearStretchContext *s = ctx->priv;
+ ThreadData *td = arg;
+ AVFrame *in = td->in;
+ AVFrame *out = td->out;
+ int plane;
+
+ for (plane = 0; plane < s->nb_planes; plane++) {
+ const int plane_type = plane == 1 || plane == 2 ? 1 : 0;
+
+ const int width = s->plane_width[plane_type];
+ const int height = s->plane_height[plane_type];
+
+ const int slice_start = height * job / nb_jobs;
+ const int slice_end = height * (job+1) / nb_jobs;
+
+ uint8_t *dst = out->data[plane] + slice_start * out->linesize[plane];
+ const uint8_t *src = in->data[plane] + slice_start * in->linesize[plane];
+
+ stretch_frame(width, (slice_end - slice_start),
+ dst, out->linesize[plane],
+ src, in->linesize[plane],
+ s->plane_xmap[plane_type], s->interpolate);
+ }
+
+ return 0;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+ AVFilterContext *ctx = inlink->dst;
+ AVFilterLink *outlink = ctx->outputs[0];
+ ThreadData td;
+
+ AVFrame *out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
+ if (!out) {
+ av_frame_free(&in);
+ return AVERROR(ENOMEM);
+ }
+
+ av_frame_copy_props(out, in);
+ out->width = outlink->w;
+ out->height = outlink->h;
+
+ td.in = in;
+ td.out = out;
+ ctx->internal->execute(ctx, filter_slice, &td, NULL, FFMIN(outlink->h, ff_filter_get_nb_threads(ctx)));
+
+ av_frame_free(&in);
+
+ return ff_filter_frame(outlink, out);
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+ NonlinearStretchContext *s = ctx->priv;
+ av_freep(&s->plane_xmap[0]);
+ av_freep(&s->plane_xmap[1]);
+}
+
+static const AVFilterPad nonlinearstretch_inputs[] = {
+ {
+ .name = "default",
+ .type = AVMEDIA_TYPE_VIDEO,
+ .filter_frame = filter_frame,
+ },
+ { NULL }
+};
+
+static const AVFilterPad nonlinearstretch_outputs[] = {
+ {
+ .name = "default",
+ .type = AVMEDIA_TYPE_VIDEO,
+ .config_props = config_props,
+ },
+ { NULL }
+};
+
+AVFilter ff_vf_nonlinearstretch = {
+ .name = "nonlinearstretch",
+ .description = NULL_IF_CONFIG_SMALL("Stretch input video nonlinearly."),
+ .priv_size = sizeof(NonlinearStretchContext),
+ .uninit = uninit,
+ .query_formats = query_formats,
+ .inputs = nonlinearstretch_inputs,
+ .outputs = nonlinearstretch_outputs,
+ .priv_class = &nonlinearstretch_class,
+ .flags = AVFILTER_FLAG_SLICE_THREADS | AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,
+};
diff --git a/tests/fate/filter-video.mak b/tests/fate/filter-video.mak
index 18fe4f7016..adbb31b33f 100644
--- a/tests/fate/filter-video.mak
+++ b/tests/fate/filter-video.mak
@@ -555,6 +555,9 @@ fate-filter-hue4: CMD = video_filter "format=yuv422p10,perms=random,hue=h=18*n:s
FATE_FILTER_VSYNTH-$(CONFIG_IDET_FILTER) += fate-filter-idet
fate-filter-idet: CMD = framecrc -flags bitexact -idct simple -i $(SRC) -vf idet -frames:v 25 -flags +bitexact
+FATE_FILTER_VSYNTH-$(call ALLYES, FORMAT_FILTER PERMS_FILTER NONLINEARSTRETCH_FILTER) += fate-filter-nonlinearstretch
+fate-filter-nonlinearstretcH: CMD = video_filter "format=gbrp,perms=random,nonlinearstretch=width=1920" -frames:v 20
+
FATE_FILTER_VSYNTH-$(CONFIG_PAD_FILTER) += fate-filter-pad
fate-filter-pad: CMD = video_filter "pad=iw*1.5:ih*1.5:iw*0.3:ih*0.2"
--
2.23.0
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