[FFmpeg-devel] [PATCH 1/1] Add fifo filter.

[Stefano Sabatini]

---
 doc/filters.texi         |    9 ++++
 libavfilter/Makefile     |    1 +
 libavfilter/allfilters.c |    1 +
 libavfilter/vf_fifo.c    |  116 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 127 insertions(+), 0 deletions(-)
 create mode 100644 libavfilter/vf_fifo.c

diff --git a/doc/filters.texi b/doc/filters.texi
index 7f0cb71..40cdb92 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -39,6 +39,15 @@ corner of the input image.
 
 The default value of @var{width} and @var{height} is 0.
 
+ at section fifo
+
+Buffer input images and send them when they are requested.
+
+This filter is mainly useful when auto-inserted by the libavfilter
+framework.
+
+The filter does not take parameters.
+
 @section format
 
 Convert the input video to one of the specified pixel formats.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index feef16c..fd61b49 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -16,6 +16,7 @@ OBJS = allfilters.o                                                     \
 
 OBJS-$(CONFIG_ASPECT_FILTER)                 += vf_aspect.o
 OBJS-$(CONFIG_CROP_FILTER)                   += vf_crop.o
+OBJS-$(CONFIG_FIFO_FILTER)                   += vf_fifo.o
 OBJS-$(CONFIG_FORMAT_FILTER)                 += vf_format.o
 OBJS-$(CONFIG_NOFORMAT_FILTER)               += vf_format.o
 OBJS-$(CONFIG_NULL_FILTER)                   += vf_null.o
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index e8bc771..2f31751 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -36,6 +36,7 @@ void avfilter_register_all(void)
 
     REGISTER_FILTER (ASPECT,      aspect,      vf);
     REGISTER_FILTER (CROP,        crop,        vf);
+    REGISTER_FILTER (FIFO,        fifo,        vf);
     REGISTER_FILTER (FORMAT,      format,      vf);
     REGISTER_FILTER (NOFORMAT,    noformat,    vf);
     REGISTER_FILTER (NULL,        null,        vf);
diff --git a/libavfilter/vf_fifo.c b/libavfilter/vf_fifo.c
new file mode 100644
index 0000000..5ba753f
--- /dev/null
+++ b/libavfilter/vf_fifo.c
@@ -0,0 +1,116 @@
+/*
+ * copyright (c) 2007 Bobby Bingham
+ *
+ * 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
+ * FIFO buffering video filter
+ */
+
+#include "avfilter.h"
+
+typedef struct BufPic {
+    AVFilterBufferRef *pic;
+    struct BufPic     *next;
+} BufPic;
+
+typedef struct {
+    BufPic  root;
+    BufPic *last;   ///< last buffered picture
+} FifoContext;
+
+static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
+{
+    FifoContext *fifo = ctx->priv;
+    fifo->last = &fifo->root;
+
+    return 0;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    FifoContext *fifo = ctx->priv;
+    BufPic *pic, *tmp;
+
+    for (pic = fifo->root.next; pic; pic = tmp) {
+        tmp = pic->next;
+        avfilter_unref_buffer(pic->pic);
+        av_free(pic);
+    }
+}
+
+static void start_frame(AVFilterLink *inlink, AVFilterBufferRef *picref)
+{
+    FifoContext *fifo = inlink->dst->priv;
+
+    fifo->last->next = av_mallocz(sizeof(BufPic));
+    fifo->last = fifo->last->next;
+    fifo->last->pic = picref;
+}
+
+static void end_frame(AVFilterLink *inlink) { }
+
+static void draw_slice(AVFilterLink *inlink, int y, int h, int slice_dir) { }
+
+static int request_frame(AVFilterLink *outlink)
+{
+    FifoContext *fifo = outlink->src->priv;
+    BufPic *tmp;
+
+    if (!fifo->root.next)
+        if (avfilter_request_frame(outlink->src->inputs[0]))
+            return -1;
+
+    /* by doing this, we give ownership of the reference to the next filter,
+     * so we don't have to worry about dereferencing it ourselves. */
+    avfilter_start_frame(outlink, fifo->root.next->pic);
+    avfilter_draw_slice (outlink, 0, fifo->root.next->pic->video->h, 1);
+    avfilter_end_frame  (outlink);
+
+    if (fifo->last == fifo->root.next)
+        fifo->last = &fifo->root;
+    tmp = fifo->root.next->next;
+    av_free(fifo->root.next);
+    fifo->root.next = tmp;
+
+    return 0;
+}
+
+AVFilter avfilter_vf_fifo = {
+    .name      = "fifo",
+    .description = NULL_IF_CONFIG_SMALL("Buffer input images and send them when they are requested."),
+
+    .init      = init,
+    .uninit    = uninit,
+
+    .priv_size = sizeof(FifoContext),
+
+    .inputs    = (AVFilterPad[]) {{ .name            = "default",
+                                    .type            = AVMEDIA_TYPE_VIDEO,
+                                    .get_video_buffer= avfilter_null_get_video_buffer,
+                                    .start_frame     = start_frame,
+                                    .draw_slice      = draw_slice,
+                                    .end_frame       = end_frame,
+                                    .rej_perms       = AV_PERM_REUSE2, },
+                                  { .name = NULL}},
+    .outputs   = (AVFilterPad[]) {{ .name            = "default",
+                                    .type            = AVMEDIA_TYPE_VIDEO,
+                                    .request_frame   = request_frame, },
+                                  { .name = NULL}},
+};
-- 
1.7.0.4