avfilter: add random video filter

Signed-off-by: Paul B Mahol <onemda@gmail.com>

1 files changed, 144 insertions, 0 deletions

diff --git a/libavfilter/vf_random.c b/libavfilter/vf_random.c
new file mode 100644
index 0000000..663fafc
--- /dev/null
+++ b/libavfilter/vf_random.c
@@ -0,0 +1,144 @@
+/*
+ * Copyright (c) 2015 Paul B Mahol
+ *
+ * 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/lfg.h"
+#include "libavutil/opt.h"
+#include "libavutil/random_seed.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+
+#define MAX_FRAMES 512
+
+typedef struct RandomContext {
+    const AVClass *class;
+
+    AVLFG lfg;
+    int nb_frames;
+    int64_t random_seed;
+    int nb_frames_filled;
+    AVFrame *frames[MAX_FRAMES];
+    int64_t pts[MAX_FRAMES];
+    int flush_idx;
+} RandomContext;
+
+#define OFFSET(x) offsetof(RandomContext, x)
+#define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
+
+static const AVOption random_options[] = {
+    { "frames", "set number of frames in cache", OFFSET(nb_frames),   AV_OPT_TYPE_INT,   {.i64=30},  2, MAX_FRAMES, FLAGS },
+    { "seed",   "set the seed",                  OFFSET(random_seed), AV_OPT_TYPE_INT64, {.i64=-1}, -1, UINT32_MAX, FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(random);
+
+static av_cold int init(AVFilterContext *ctx)
+{
+    RandomContext *s = ctx->priv;
+    uint32_t seed;
+
+    if (s->random_seed < 0)
+        s->random_seed = av_get_random_seed();
+    seed = s->random_seed;
+    av_lfg_init(&s->lfg, seed);
+
+    return 0;
+}
+
+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;
+    RandomContext *s = ctx->priv;
+    AVFilterLink *outlink = ctx->outputs[0];
+    AVFrame *out;
+    int idx;
+
+    if (s->nb_frames_filled < s->nb_frames) {
+        s->frames[s->nb_frames_filled] = in;
+        s->pts[s->nb_frames_filled++] = in->pts;
+        return 0;
+    }
+
+    idx = av_lfg_get(&s->lfg) % s->nb_frames;
+
+    out = s->frames[idx];
+    out->pts = s->pts[0];
+    memmove(&s->pts[0], &s->pts[1], (s->nb_frames - 1) * sizeof(s->pts[0]));
+    s->frames[idx] = in;
+    s->pts[s->nb_frames - 1] = in->pts;
+
+    return ff_filter_frame(outlink, out);
+}
+
+static int request_frame(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    RandomContext *s = ctx->priv;
+    int ret;
+
+    ret = ff_request_frame(ctx->inputs[0]);
+
+    if (ret == AVERROR_EOF && !ctx->is_disabled && 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->frames[s->nb_frames - 1] = NULL;
+        s->nb_frames--;
+    }
+
+    return ret;
+}
+
+static const AVFilterPad random_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .filter_frame = filter_frame,
+    },
+    { NULL }
+};
+
+static const AVFilterPad random_outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_VIDEO,
+        .request_frame = request_frame,
+        .config_props  = config_output,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_random = {
+    .name        = "random",
+    .description = NULL_IF_CONFIG_SMALL("Return random frames."),
+    .priv_size   = sizeof(RandomContext),
+    .priv_class  = &random_class,
+    .init        = init,
+    .inputs      = random_inputs,
+    .outputs     = random_outputs,
+};