lavfi: add setfield filter

Changelog

@@ -3,6 +3,8 @@ releases are sorted from youngest to oldest.
 
 version next:
 - v408 Quicktime and Microsoft AYUV Uncompressed 4:4:4:4 encoder and decoder
+- setfield filter
+
 
 version 0.10:
 - Fixes: CVE-2011-3929, CVE-2011-3934, CVE-2011-3935, CVE-2011-3936,

doc/filters.texi

@@ -2385,6 +2385,28 @@ To change the sample aspect ratio to 10:11, specify:
 setsar=10:11
 @end example
 
+@section setfield
+
+Force field for the output video frame.
+
+The @code{setfield} filter marks the interlace type field for the
+output frames. It does not change the input frame, but only sets the
+corresponding property, which affects how the frame is treated by
+followig filters (e.g. @code{fieldorder} or @code{yadif}).
+
+It accepts a parameter representing an integer or a string, which can
+assume the following values:
+@table @samp
+@item -1, auto
+Keep the same field property.
+
+@item 0, bff
+Mark the frame as bottom-field-first.
+
+@item 1, tff
+Mark the frame as top-field-first.
+@end table
+
 @section setpts
 
 Change the PTS (presentation timestamp) of the input video frames.

libavfilter/Makefile

@@ -79,6 +79,7 @@ OBJS-$(CONFIG_PIXDESCTEST_FILTER)            += vf_pixdesctest.o
 OBJS-$(CONFIG_SCALE_FILTER)                  += vf_scale.o
 OBJS-$(CONFIG_SELECT_FILTER)                 += vf_select.o
 OBJS-$(CONFIG_SETDAR_FILTER)                 += vf_aspect.o
+OBJS-$(CONFIG_SETFIELD_FILTER)               += vf_setfield.o
 OBJS-$(CONFIG_SETPTS_FILTER)                 += vf_setpts.o
 OBJS-$(CONFIG_SETSAR_FILTER)                 += vf_aspect.o
 OBJS-$(CONFIG_SETTB_FILTER)                  += vf_settb.o

libavfilter/allfilters.c

@@ -87,6 +87,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER (SCALE,       scale,       vf);
     REGISTER_FILTER (SELECT,      select,      vf);
     REGISTER_FILTER (SETDAR,      setdar,      vf);
+    REGISTER_FILTER (SETFIELD,    setfield,    vf);
     REGISTER_FILTER (SETPTS,      setpts,      vf);
     REGISTER_FILTER (SETSAR,      setsar,      vf);
     REGISTER_FILTER (SETTB,       settb,       vf);

libavfilter/version.h

@@ -29,7 +29,7 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  2
-#define LIBAVFILTER_VERSION_MINOR 61
+#define LIBAVFILTER_VERSION_MINOR 62
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \

libavfilter/vf_setfield.c

@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2012 Stefano Sabatini
+ *
+ * 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
+ * set field order
+ */
+
+#include "avfilter.h"
+
+typedef struct {
+    int top_field_first;
+} SetFieldContext;
+
+static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
+{
+    SetFieldContext *setfield = ctx->priv;
+
+    setfield->top_field_first = -1;
+
+    if (args) {
+        char c;
+        if (sscanf(args, "%d%c", &setfield->top_field_first, &c) != 1) {
+            if      (!strcmp("tff",  args)) setfield->top_field_first = 1;
+            else if (!strcmp("bff",  args)) setfield->top_field_first = 0;
+            else if (!strcmp("auto", args)) setfield->top_field_first = -1;
+            else {
+                av_log(ctx, AV_LOG_ERROR, "Invalid argument '%s'\n", args);
+                return AVERROR(EINVAL);
+            }
+        }
+    }
+
+    if (setfield->top_field_first < -1 || setfield->top_field_first > 1) {
+        av_log(ctx, AV_LOG_ERROR,
+               "Provided integer value %d must be included between -1 and +1\n",
+               setfield->top_field_first);
+        return AVERROR(EINVAL);
+    }
+
+    return 0;
+}
+
+static void start_frame(AVFilterLink *inlink, AVFilterBufferRef *inpicref)
+{
+    SetFieldContext *setfield = inlink->dst->priv;
+    AVFilterBufferRef *outpicref = avfilter_ref_buffer(inpicref, ~0);
+
+    if (setfield->top_field_first != -1) {
+        outpicref->video->interlaced = 1;
+        outpicref->video->top_field_first = setfield->top_field_first;
+    }
+    avfilter_start_frame(inlink->dst->outputs[0], outpicref);
+}
+
+AVFilter avfilter_vf_setfield = {
+    .name      = "setfield",
+    .description = NULL_IF_CONFIG_SMALL("Force field for the output video frame."),
+    .init      = init,
+
+    .priv_size = sizeof(SetFieldContext),
+
+    .inputs = (const AVFilterPad[]) {
+        { .name             = "default",
+          .type             = AVMEDIA_TYPE_VIDEO,
+          .get_video_buffer = avfilter_null_get_video_buffer,
+          .start_frame      = start_frame, },
+        { .name = NULL }
+    },
+    .outputs = (const AVFilterPad[]) {
+        { .name             = "default",
+          .type             = AVMEDIA_TYPE_VIDEO, },
+        { .name = NULL }
+    },
+};