lavfi: add field filter

The filter is a port of libmpcodecs/vf_field.c, since there is no common
code I relicensed it as LGPL, while keeping the original author
copyright.

1 files changed, 145 insertions, 0 deletions

diff --git a/libavfilter/vf_field.c b/libavfilter/vf_field.c
new file mode 100644
index 0000000000..c9ac42b20a
--- /dev/null
+++ b/libavfilter/vf_field.c
@@ -0,0 +1,145 @@
+/*
+ * Copyright (c) 2003 Rich Felker
+ * 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
+ * field filter, based on libmpcodecs/vf_field.c by Rich Felker
+ */
+
+#include "libavutil/opt.h"
+#include "libavutil/pixdesc.h"
+#include "avfilter.h"
+#include "internal.h"
+
+enum FieldType { FIELD_TYPE_TOP = 0, FIELD_TYPE_BOTTOM };
+
+typedef struct {
+    const AVClass *class;
+    enum FieldType type;
+    int nb_planes;              ///< number of planes of the current format
+} FieldContext;
+
+#define OFFSET(x) offsetof(FieldContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+
+static const AVOption field_options[] = {
+    {"type", "set field type (top or bottom)", OFFSET(type), AV_OPT_TYPE_INT, {.i64=FIELD_TYPE_TOP}, 0, 1, FLAGS, "field_type" },
+    {"top",    "select top field",    0, AV_OPT_TYPE_CONST, {.i64=FIELD_TYPE_TOP},    INT_MIN, INT_MAX, FLAGS, "field_type"},
+    {"bottom", "select bottom field", 0, AV_OPT_TYPE_CONST, {.i64=FIELD_TYPE_BOTTOM}, INT_MIN, INT_MAX, FLAGS, "field_type"},
+
+    {NULL}
+};
+
+AVFILTER_DEFINE_CLASS(field);
+
+static av_cold int init(AVFilterContext *ctx, const char *args)
+{
+    FieldContext *field = ctx->priv;
+    static const char *shorthand[] = { "type", NULL };
+
+    field->class = &field_class;
+    av_opt_set_defaults(field);
+
+    return av_opt_set_from_string(field, args, shorthand, "=", ":");
+}
+
+static int config_props_output(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    FieldContext *field = ctx->priv;
+    AVFilterLink *inlink = ctx->inputs[0];
+    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
+    int i;
+
+    for (i = 0; i < desc->nb_components; i++)
+        field->nb_planes = FFMAX(field->nb_planes, desc->comp[i].plane);
+    field->nb_planes++;
+
+    outlink->w = inlink->w;
+    outlink->h = (inlink->h + (field->type == FIELD_TYPE_TOP)) / 2;
+
+    av_log(ctx, AV_LOG_VERBOSE, "w:%d h:%d type:%s -> w:%d h:%d\n",
+           inlink->w, inlink->h, field->type == FIELD_TYPE_BOTTOM ? "bottom" : "top",
+           outlink->w, outlink->h);
+    return 0;
+}
+
+static int start_frame(AVFilterLink *inlink, AVFilterBufferRef *inpicref)
+{
+    FieldContext *field = inlink->dst->priv;
+    AVFilterBufferRef *outpicref = avfilter_ref_buffer(inpicref, ~0);
+    AVFilterLink *outlink = inlink->dst->outputs[0];
+    int i;
+
+    if (!outpicref)
+        return AVERROR(ENOMEM);
+
+    outpicref->video->h = outlink->h;
+    outpicref->video->interlaced = 0;
+
+    for (i = 0; i < field->nb_planes; i++) {
+        if (field->type == FIELD_TYPE_BOTTOM)
+            outpicref->data[i] = inpicref->data[i] + inpicref->linesize[i];
+        outpicref->linesize[i] = 2 * inpicref->linesize[i];
+    }
+    return ff_start_frame(outlink, outpicref);
+}
+
+static int draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir)
+{
+    FieldContext *field = inlink->dst->priv;
+    int y1 = (y + (field->type == FIELD_TYPE_TOP)) / 2;
+    int h1 = (h + (field->type == FIELD_TYPE_TOP)) / 2;
+    return ff_draw_slice(inlink->dst->outputs[0], y1, h1, slice_dir);
+}
+
+static const AVFilterPad field_inputs[] = {
+    {
+        .name             = "default",
+        .type             = AVMEDIA_TYPE_VIDEO,
+        .get_video_buffer = ff_null_get_video_buffer,
+        .start_frame      = start_frame,
+        .draw_slice       = draw_slice,
+        .end_frame        = ff_null_end_frame,
+    },
+    { NULL }
+};
+
+static const AVFilterPad field_outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_VIDEO,
+        .config_props  = config_props_output,
+    },
+    { NULL }
+};
+
+AVFilter avfilter_vf_field = {
+    .name          = "field",
+    .description   = NULL_IF_CONFIG_SMALL("Extract a field from the input video."),
+
+    .priv_size     = sizeof(FieldContext),
+    .init          = init,
+
+    .inputs        = field_inputs,
+    .outputs       = field_outputs,
+    .priv_class    = &field_class,
+};