1. ffmpeg
  2. Commit 48d116400cb321dd045bcf6836d1270b1d2b6f74
Browse code

lavfi: add framestep filter

This filter is inspired upon libmpcodecs/vf_framestep.c, by Daniele
Forghieri.

Only-keyframe output is not supported, since that feature can be achieved
through the more versatile select filter.

Stefano Sabatini authored on 2012/08/17 02:04:26
Showing 6 changed files
Changelog
History View file @ 48d1164
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@@ -48,6 +48,7 @@ version next:
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 - ICO muxer
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 - SubRip encoder and decoder without embedded timing
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 - edge detection filter
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+- framestep filter
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 version 0.11:
doc/filters.texi
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@@ -2084,6 +2084,13 @@ Desired output framerate.
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 @end table
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+@section framestep
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+
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+Select one frame every N.
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+
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+This filter accepts in input a string representing a positive
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+integer. Default argument is @code{1}.
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+
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 @anchor{frei0r}
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 @section frei0r
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libavfilter/Makefile
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... ... 
@@ -95,6 +95,7 @@ OBJS-$(CONFIG_FADE_FILTER)                   += vf_fade.o
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 OBJS-$(CONFIG_FIELDORDER_FILTER)             += vf_fieldorder.o
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 OBJS-$(CONFIG_FIFO_FILTER)                   += fifo.o
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 OBJS-$(CONFIG_FORMAT_FILTER)                 += vf_format.o
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+OBJS-$(CONFIG_FRAMESTEP_FILTER)              += vf_framestep.o
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 OBJS-$(CONFIG_FPS_FILTER)                    += vf_fps.o
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 OBJS-$(CONFIG_FREI0R_FILTER)                 += vf_frei0r.o
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 OBJS-$(CONFIG_GRADFUN_FILTER)                += vf_gradfun.o
libavfilter/allfilters.c
History View file @ 48d1164
... ... 
@@ -87,6 +87,7 @@ void avfilter_register_all(void)
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     REGISTER_FILTER (FIFO,        fifo,        vf);
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     REGISTER_FILTER (FORMAT,      format,      vf);
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     REGISTER_FILTER (FPS,         fps,         vf);
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+    REGISTER_FILTER (FRAMESTEP,   framestep,   vf);
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     REGISTER_FILTER (FREI0R,      frei0r,      vf);
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     REGISTER_FILTER (GRADFUN,     gradfun,     vf);
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     REGISTER_FILTER (HFLIP,       hflip,       vf);
libavfilter/version.h
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@@ -29,8 +29,8 @@
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 #include "libavutil/avutil.h"
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 #define LIBAVFILTER_VERSION_MAJOR  3
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-#define LIBAVFILTER_VERSION_MINOR  10
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-#define LIBAVFILTER_VERSION_MICRO 101
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+#define LIBAVFILTER_VERSION_MINOR  11
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+#define LIBAVFILTER_VERSION_MICRO 100
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 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
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                                                LIBAVFILTER_VERSION_MINOR, \
libavfilter/vf_framestep.c
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new file mode 100644
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@@ -0,0 +1,142 @@
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+/*
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+ * Copyright (c) 2012 Stefano Sabatini
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+ *
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+ * This file is part of FFmpeg.
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+ *
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+ * FFmpeg is free software; you can redistribute it and/or
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+ * modify it under the terms of the GNU Lesser General Public
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+ * License as published by the Free Software Foundation; either
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+ * version 2.1 of the License, or (at your option) any later version.
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+ *
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+ * FFmpeg is distributed in the hope that it will be useful,
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+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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+ * Lesser General Public License for more details.
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+ *
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+ * You should have received a copy of the GNU Lesser General Public
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+ * License along with FFmpeg; if not, write to the Free Software
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+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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+ */
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+
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+/**
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+ * @file framestep filter, inspired on libmpcodecs/vf_framestep.c by
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+ * Daniele Fornighieri <guru AT digitalfantasy it>.
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+ */
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+
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+#include "avfilter.h"
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+#include "internal.h"
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+#include "video.h"
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+
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+typedef struct {
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+    int frame_step, frame_count, frame_selected;
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+} FrameStepContext;
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+
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+static av_cold int init(AVFilterContext *ctx, const char *args)
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+{
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+    FrameStepContext *framestep = ctx->priv;
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+    char *tailptr;
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+    long int n;
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+
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+    framestep->frame_step = 1;
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+
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+    if (args) {
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+        n = strtol(args, &tailptr, 10);
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+        if (*tailptr || n <= 0 || n >= INT_MAX) {
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+            av_log(ctx, AV_LOG_ERROR,
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+                   "Invalid argument '%s', must be a positive integer <= INT_MAX\n", args);
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+            return AVERROR(EINVAL);
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+        }
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+    }
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+
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+    framestep->frame_step = n;
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+    return 0;
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+}
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+
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+static int config_output_props(AVFilterLink *outlink)
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+{
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+    AVFilterContext *ctx = outlink->src;
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+    FrameStepContext *framestep = ctx->priv;
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+    AVFilterLink *inlink = ctx->inputs[0];
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+
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+    outlink->frame_rate =
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+        av_div_q(inlink->frame_rate, (AVRational){framestep->frame_step, 1});
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+
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+    av_log(ctx, AV_LOG_VERBOSE, "step:%d frame_rate:%d/%d(%f) -> frame_rate:%d/%d(%f)\n",
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+           framestep->frame_step,
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+           inlink->frame_rate.num, inlink->frame_rate.den, av_q2d(inlink->frame_rate),
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+           outlink->frame_rate.num, outlink->frame_rate.den, av_q2d(outlink->frame_rate));
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+    return 0;
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+}
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+
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+static int start_frame(AVFilterLink *inlink, AVFilterBufferRef *ref)
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+{
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+    FrameStepContext *framestep = inlink->dst->priv;
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+
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+    framestep->frame_selected = 0;
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+    if (!(framestep->frame_count++ % framestep->frame_step)) {
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+        inlink->cur_buf = NULL;
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+        framestep->frame_selected = 1;
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+        return ff_start_frame(inlink->dst->outputs[0], ref);
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+    }
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+    return 0;
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+}
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+
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+static int draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir)
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+{
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+    FrameStepContext *framestep = inlink->dst->priv;
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+
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+    if (framestep->frame_selected)
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+        return ff_draw_slice(inlink->dst->outputs[0], y, h, slice_dir);
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+    return 0;
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+}
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+
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+static int end_frame(AVFilterLink *inlink)
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+{
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+    FrameStepContext *framestep = inlink->dst->priv;
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+
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+    if (framestep->frame_selected)
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+        return ff_end_frame(inlink->dst->outputs[0]);
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+    return 0;
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+}
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+
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+static int request_frame(AVFilterLink *outlink)
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+{
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+    FrameStepContext *framestep = outlink->src->priv;
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+    AVFilterLink *inlink = outlink->src->inputs[0];
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+    int ret;
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+
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+    framestep->frame_selected = 0;
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+    do {
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+        ret = ff_request_frame(inlink);
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+    } while (!framestep->frame_selected && ret >= 0);
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+
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+    return ret;
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+}
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+
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+AVFilter avfilter_vf_framestep = {
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+    .name      = "framestep",
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+    .description = NULL_IF_CONFIG_SMALL("Select one frame every N frames."),
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+    .init      = init,
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+    .priv_size = sizeof(FrameStepContext),
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+
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+    .inputs = (const AVFilterPad[]) {
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+        {
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+            .name             = "default",
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+            .type             = AVMEDIA_TYPE_VIDEO,
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+            .get_video_buffer = ff_null_get_video_buffer,
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+            .start_frame      = start_frame,
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+            .draw_slice       = draw_slice,
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+            .end_frame        = end_frame,
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+        },
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+        { .name = NULL }
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+    },
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+    .outputs = (const AVFilterPad[]) {
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+        {
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+            .name             = "default",
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+            .type             = AVMEDIA_TYPE_VIDEO,
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+            .config_props     = config_output_props,
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+            .request_frame    = request_frame,
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+        },
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+        { .name = NULL }
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+    },
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+};