vf_duration.patch

diff --git a/libavcodec/libvpxenc.c b/libavcodec/libvpxenc.c
index 992122c..5903d5c 100644
--- a/libavcodec/libvpxenc.c
+++ b/libavcodec/libvpxenc.c
@@ -898,8 +898,10 @@ static int vp8_encode(AVCodecContext *avctx, AVPacket *pkt,
             flags |= VPX_EFLAG_FORCE_KF;
     }

+    av_log(avctx, AV_LOG_WARNING, "duration: (%d)\n", frame->pkt_duration);
     res = vpx_codec_encode(&ctx->encoder, rawimg, timestamp,
-                           avctx->ticks_per_frame, flags, ctx->deadline);
+                           frame->pkt_duration || avctx->ticks_per_frame,
+                           flags, ctx->deadline);
     if (res != VPX_CODEC_OK) {
         log_encoder_error(avctx, "Error encoding frame");
         return AVERROR_INVALIDDATA;
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index a095a10..95cc658 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -131,6 +131,7 @@ OBJS-$(CONFIG_DRAWBOX_FILTER)                += vf_drawbox.o
 OBJS-$(CONFIG_DRAWGRAPH_FILTER)              += f_drawgraph.o
 OBJS-$(CONFIG_DRAWGRID_FILTER)               += vf_drawbox.o
 OBJS-$(CONFIG_DRAWTEXT_FILTER)               += vf_drawtext.o
+OBJS-$(CONFIG_DURATION_FILTER)               += vf_duration.o
 OBJS-$(CONFIG_ELBG_FILTER)                   += vf_elbg.o
 OBJS-$(CONFIG_EDGEDETECT_FILTER)             += vf_edgedetect.o
 OBJS-$(CONFIG_EQ_FILTER)                     += vf_eq.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 3ab9a48..91c8ad5 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -153,6 +153,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(DRAWGRAPH,      drawgraph,      vf);
     REGISTER_FILTER(DRAWGRID,       drawgrid,       vf);
     REGISTER_FILTER(DRAWTEXT,       drawtext,       vf);
+    REGISTER_FILTER(DURATION,       duration,       vf);
     REGISTER_FILTER(EDGEDETECT,     edgedetect,     vf);
     REGISTER_FILTER(ELBG,           elbg,           vf);
     REGISTER_FILTER(EQ,             eq,             vf);
diff --git a/libavfilter/vf_duration.c b/libavfilter/vf_duration.c
new file mode 100644
index 0000000..bbc40b7
--- /dev/null
+++ b/libavfilter/vf_duration.c
@@ -0,0 +1,105 @@
+/*
+ * 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 vf_duration filter, fill frame->pkt_duration field
+ */
+
+#include "libavutil/internal.h"
+#include "avfilter.h"
+#include "internal.h"
+#include "video.h"
+
+typedef struct {
+    const AVClass *class;
+    AVFrame *prev;
+} DurationContext;
+
+static const AVFilterPad avfilter_vf_duration_inputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+    { NULL }
+};
+
+static const AVFilterPad avfilter_vf_duration_outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_VIDEO,
+    },
+    { NULL }
+};
+
+static av_cold void init(AVFilterContext *ctx)
+{
+    DurationContext *duration = ctx->priv;
+    duration->prev = 0;
+    //return ff_filter_frame(outlink, duration->prev);
+    return 0;
+};
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    DurationContext *duration = ctx->priv;
+    //return ff_filter_frame(outlink, duration->prev);
+    return 0;
+};
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    DurationContext *duration = inlink->dst->priv;
+    int ret;
+
+    if (duration->prev) {
+        AVFilterLink *outlink = inlink->dst->outputs[0];
+        AVFrame *out = ff_get_video_buffer(outlink, in->width, in->height);
+        if (!out) {
+            av_frame_free(&duration->prev);
+            av_frame_free(&in);
+            return AVERROR(ENOMEM);
+        }
+        av_frame_copy_props(out, duration->prev);
+        av_frame_copy(out, duration->prev);
+        out->pkt_duration = in->pts - out->pts;
+        av_frame_free(&duration->prev);
+        duration->prev = in;
+        return ff_filter_frame(outlink, out);
+    };
+    duration->prev = in;
+    return 0;
+};
+
+static const AVFilterPad duration_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .filter_frame = filter_frame,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_duration = {
+    .name        = "duration",
+    .description = NULL_IF_CONFIG_SMALL("Fill frame display duraion field."),
+    .init          = init,
+    .uninit        = uninit,
+    .priv_size   = sizeof(DurationContext),
+    .inputs      = duration_inputs,
+    .outputs     = avfilter_vf_duration_outputs,
+};