Add the null video filter.

Originally committed as revision 20275 to svn://svn.ffmpeg.org/ffmpeg/trunk

doc/vfilters.texi

@@ -78,4 +78,8 @@ build.
 
 Below is a description of the currently available video filters.
 
+@section null
+
+Pass the source unchanged to the output.
+
 @bye

libavfilter/Makefile

@@ -11,6 +11,6 @@ OBJS = allfilters.o                                                     \
        defaults.o                                                       \
        formats.o                                                        \
 
-#OBJS-$(CONFIG_XXX_FILTER)    += vf_xxx.o
+OBJS-$(CONFIG_NULL_FILTER)    += vf_null.o
 
 include $(SUBDIR)../subdir.mak

libavfilter/allfilters.c

@@ -34,6 +34,5 @@ void avfilter_register_all(void)
         return;
     initialized = 1;
 
-//    REGISTER_FILTER (CROP,crop,vf);
-
+    REGISTER_FILTER (NULL,null,vf);
 }

libavfilter/vf_null.c

@@ -0,0 +1,56 @@
+/*
+ * 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 libavfilter/vf_null.c
+ * null filter
+ */
+
+#include "avfilter.h"
+
+static AVFilterPicRef *get_video_buffer(AVFilterLink *link, int perms, int w, int h)
+{
+    return avfilter_get_video_buffer(link->dst->outputs[0], perms, w, h);
+}
+
+static void start_frame(AVFilterLink *link, AVFilterPicRef *picref)
+{
+    avfilter_start_frame(link->dst->outputs[0], picref);
+}
+
+static void end_frame(AVFilterLink *link)
+{
+    avfilter_end_frame(link->dst->outputs[0]);
+}
+
+AVFilter avfilter_vf_null = {
+    .name      = "null",
+
+    .priv_size = 0,
+
+    .inputs    = (AVFilterPad[]) {{ .name             = "default",
+                                    .type             = CODEC_TYPE_VIDEO,
+                                    .get_video_buffer = get_video_buffer,
+                                    .start_frame      = start_frame,
+                                    .end_frame        = end_frame },
+                                  { .name = NULL}},
+
+    .outputs   = (AVFilterPad[]) {{ .name             = "default",
+                                    .type             = CODEC_TYPE_VIDEO, },
+                                  { .name = NULL}},
+};