[FFmpeg-devel] [PATCH] separatefields filter

[Paul B Mahol]

Signed-off-by: Paul B Mahol <onemda at gmail.com>
---
 doc/filters.texi                |  10 ++++
 libavfilter/Makefile            |   1 +
 libavfilter/allfilters.c        |   1 +
 libavfilter/vf_separatefields.c | 108 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 120 insertions(+)
 create mode 100644 libavfilter/vf_separatefields.c

diff --git a/doc/filters.texi b/doc/filters.texi
index 483d8a1..8172a44 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -4896,6 +4896,16 @@ scale='min(500\, iw*3/2):-1'
 @end example
 @end itemize
 
+ at section separatefields
+
+Separate fields takes a frame-based video input and splits each frame
+into its components fields, producing a new half height clip with
+twice the frame rate and twice the frame count.
+
+This filter use field-dominance information in frame to decide which
+of each pair of fields to place first in the output.
+If it gets it wrong use @code{setfield} filter before @code{separatefields} filter.
+
 @section setdar, setsar
 
 The @code{setdar} filter sets the Display Aspect Ratio for the filter
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index e1eb35d..d91529d 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -148,6 +148,7 @@ OBJS-$(CONFIG_PERMS_FILTER)                  += f_perms.o
 OBJS-$(CONFIG_PIXDESCTEST_FILTER)            += vf_pixdesctest.o
 OBJS-$(CONFIG_PP_FILTER)                     += vf_pp.o
 OBJS-$(CONFIG_REMOVELOGO_FILTER)             += bbox.o lswsutils.o lavfutils.o vf_removelogo.o
+OBJS-$(CONFIG_SEPARATEFIELDS_FILTER)         += vf_separatefields.o
 OBJS-$(CONFIG_SCALE_FILTER)                  += vf_scale.o
 OBJS-$(CONFIG_SELECT_FILTER)                 += f_select.o
 OBJS-$(CONFIG_SENDCMD_FILTER)                += f_sendcmd.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 4972322..e5c20ed 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -146,6 +146,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(SCALE,          scale,          vf);
     REGISTER_FILTER(SELECT,         select,         vf);
     REGISTER_FILTER(SENDCMD,        sendcmd,        vf);
+    REGISTER_FILTER(SEPARATEFIELDS, separatefields, vf);
     REGISTER_FILTER(SETDAR,         setdar,         vf);
     REGISTER_FILTER(SETFIELD,       setfield,       vf);
     REGISTER_FILTER(SETPTS,         setpts,         vf);
diff --git a/libavfilter/vf_separatefields.c b/libavfilter/vf_separatefields.c
new file mode 100644
index 0000000..ac4a1e8
--- /dev/null
+++ b/libavfilter/vf_separatefields.c
@@ -0,0 +1,108 @@
+/*
+ * Copyright (c) 2013 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/pixdesc.h"
+#include "avfilter.h"
+#include "internal.h"
+
+typedef struct {
+    int nb_planes;
+} SeparateFieldsContext;
+
+static int config_props_output(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    SeparateFieldsContext *sf = ctx->priv;
+    AVFilterLink *inlink = ctx->inputs[0];
+
+    sf->nb_planes = av_pix_fmt_count_planes(inlink->format);;
+
+    if (inlink->h & 1) {
+        av_log(ctx, AV_LOG_ERROR, "height must be even\n");
+        return AVERROR_INVALIDDATA;
+    }
+
+    outlink->time_base.num = inlink->time_base.num;
+    outlink->time_base.den = inlink->time_base.den * 2;
+    outlink->frame_rate.num = inlink->frame_rate.num * 2;
+    outlink->frame_rate.den = inlink->frame_rate.den;
+    outlink->w = inlink->w;
+    outlink->h = inlink->h / 2;
+
+    return 0;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *inpicref)
+{
+    AVFilterContext *ctx = inlink->dst;
+    SeparateFieldsContext *sf = ctx->priv;
+    AVFilterLink *outlink = ctx->outputs[0];
+    AVFrame *second;
+    int i, ret;
+
+    inpicref->height = outlink->h;
+    inpicref->interlaced_frame = 0;
+
+    second = av_frame_clone(inpicref);
+    if (!second)
+        return AVERROR(ENOMEM);
+
+    for (i = 0; i < sf->nb_planes; i++) {
+        if (!inpicref->top_field_first)
+            inpicref->data[i] = inpicref->data[i] + inpicref->linesize[i];
+        else
+            second->data[i] = second->data[i] + second->linesize[i];
+        inpicref->linesize[i] = 2 * inpicref->linesize[i];
+        second->linesize[i]   = 2 * second->linesize[i];
+    }
+
+    inpicref->pts *= 2;
+    second->pts    = inpicref->pts + 1;
+
+    ret = ff_filter_frame(outlink, inpicref);
+    return ff_filter_frame(outlink, second) | ret;
+}
+
+static const AVFilterPad separatefields_inputs[] = {
+    {
+        .name             = "default",
+        .type             = AVMEDIA_TYPE_VIDEO,
+        .get_video_buffer = ff_null_get_video_buffer,
+        .filter_frame     = filter_frame,
+    },
+    { NULL }
+};
+
+static const AVFilterPad separatefields_outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_VIDEO,
+        .config_props  = config_props_output,
+    },
+    { NULL }
+};
+
+AVFilter avfilter_vf_separatefields = {
+    .name          = "separatefields",
+    .description   = NULL_IF_CONFIG_SMALL("Split input video frames into fields."),
+    .priv_size     = sizeof(SeparateFieldsContext),
+    .inputs        = separatefields_inputs,
+    .outputs       = separatefields_outputs,
+};
-- 
1.7.11.2