avfilter: Add reverse filter

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

Changelog

@@ -18,6 +18,7 @@ version <next>:
 - libkvazaar HEVC encoder
 - erosion, dilation, deflate and inflate video filters
 - Dynamic Audio Normalizer as dynaudnorm filter
+- Reverse filter
 
 
 version 2.7:

doc/filters.texi

@@ -8418,6 +8418,22 @@ pixels will slow things down on a large logo.
 This filter uses the repeat_field flag from the Video ES headers and hard repeats
 fields based on its value.
 
+@section reverse
+
+Reverse a clip.
+
+Warning: This iflter qequires memory to buffer the entire clip, so trimming is suggested.
+
+@subsection Examples
+
+@itemize
+@item
+Take the first 5 seconds of a clip, and reverse it.
+@example
+trim=end=5,reverse
+@end example
+@end itemize
+
 @section rotate
 
 Rotate video by an arbitrary angle expressed in radians.

libavfilter/Makefile

@@ -186,6 +186,7 @@ OBJS-$(CONFIG_QP_FILTER)                     += vf_qp.o
 OBJS-$(CONFIG_REMOVEGRAIN_FILTER)            += vf_removegrain.o
 OBJS-$(CONFIG_REMOVELOGO_FILTER)             += bbox.o lswsutils.o lavfutils.o vf_removelogo.o
 OBJS-$(CONFIG_REPEATFIELDS_FILTER)           += vf_repeatfields.o
+OBJS-$(CONFIG_REVERSE_FILTER)                += vf_reverse.o
 OBJS-$(CONFIG_ROTATE_FILTER)                 += vf_rotate.o
 OBJS-$(CONFIG_SEPARATEFIELDS_FILTER)         += vf_separatefields.o
 OBJS-$(CONFIG_SAB_FILTER)                    += vf_sab.o

libavfilter/allfilters.c

@@ -201,6 +201,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(REMOVEGRAIN,    removegrain,    vf);
     REGISTER_FILTER(REMOVELOGO,     removelogo,     vf);
     REGISTER_FILTER(REPEATFIELDS,   repeatfields,   vf);
+    REGISTER_FILTER(REVERSE,        reverse,        vf);
     REGISTER_FILTER(ROTATE,         rotate,         vf);
     REGISTER_FILTER(SAB,            sab,            vf);
     REGISTER_FILTER(SCALE,          scale,          vf);

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  5
-#define LIBAVFILTER_VERSION_MINOR  23
+#define LIBAVFILTER_VERSION_MINOR  24
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \

libavfilter/vf_reverse.c

@@ -0,0 +1,142 @@
+/*
+ * Copyright (c) 2015 Derek Buitenhuis
+ *
+ * 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
+ */
+
+#include "libavutil/opt.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+
+#define DEFAULT_LENGTH 300
+
+typedef struct ReverseContext {
+    int nb_frames;
+    AVFrame **frames;
+    unsigned int frames_size;
+    unsigned int pts_size;
+    int64_t *pts;
+    int flush_idx;
+} ReverseContext;
+
+static av_cold int init(AVFilterContext *ctx)
+{
+    ReverseContext *s = ctx->priv;
+
+    s->pts = av_fast_realloc(NULL, &s->pts_size,
+                             DEFAULT_LENGTH * sizeof(*(s->pts)));
+    if (!s->pts)
+        return AVERROR(ENOMEM);
+
+    s->frames = av_fast_realloc(NULL, &s->frames_size,
+                                DEFAULT_LENGTH * sizeof(*(s->frames)));
+    if (!s->frames) {
+        av_freep(&s->pts);
+        return AVERROR(ENOMEM);
+    }
+
+    return 0;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    ReverseContext *s = ctx->priv;
+
+    av_freep(&s->pts);
+    av_freep(&s->frames);
+}
+
+static int config_output(AVFilterLink *outlink)
+{
+    outlink->flags |= FF_LINK_FLAG_REQUEST_LOOP;
+    return 0;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    AVFilterContext *ctx = inlink->dst;
+    ReverseContext *s    = ctx->priv;
+
+    if (s->nb_frames + 1 > s->frames_size / sizeof(*(s->frames))) {
+        void *ptr;
+
+        ptr = av_fast_realloc(s->pts, &s->pts_size, s->pts_size * 2);
+        if (!ptr)
+            return AVERROR(ENOMEM);
+        s->pts = ptr;
+
+        ptr = av_fast_realloc(s->frames, &s->frames_size, s->frames_size * 2);
+        if (!ptr)
+            return AVERROR(ENOMEM);
+        s->frames = ptr;
+    }
+
+    s->frames[s->nb_frames] = in;
+    s->pts[s->nb_frames]    = in->pts;
+    s->nb_frames++;
+
+    return 0;
+}
+
+static int request_frame(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    ReverseContext *s = ctx->priv;
+    int ret;
+
+    ret = ff_request_frame(ctx->inputs[0]);
+
+    if (ret == AVERROR_EOF && s->nb_frames > 0) {
+        AVFrame *out = s->frames[s->nb_frames - 1];
+        out->pts     = s->pts[s->flush_idx++];
+        ret          = ff_filter_frame(outlink, out);
+        s->nb_frames--;
+    }
+
+    return ret;
+}
+
+static const AVFilterPad reverse_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .filter_frame = filter_frame,
+    },
+    { NULL }
+};
+
+static const AVFilterPad reverse_outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_VIDEO,
+        .request_frame = request_frame,
+        .config_props  = config_output,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_reverse = {
+    .name        = "reverse",
+    .description = NULL_IF_CONFIG_SMALL("Reverse a clip."),
+    .priv_size   = sizeof(ReverseContext),
+    .init        = init,
+    .uninit      = uninit,
+    .inputs      = reverse_inputs,
+    .outputs     = reverse_outputs,
+};