avcodec: export motion vectors in frame side data on demand

The reasoning behind this addition is that various third party
applications are interested in getting some motion information out of a
video "for free" when it is available.

It was considered to export other information as well (such as the intra
information about the block, or the quantization) but the structure
might have ended up into a half full-generic, half full of codec
specific cruft. If more information is necessary, it should either be
added in the "flags" field of the AVMotionVector structure, or in
another side-data.

This commit also includes an example exporting them in a CSV stream.

1 files changed, 50 insertions, 0 deletions

diff --git a/libavutil/motion_vector.h b/libavutil/motion_vector.h
new file mode 100644
index 0000000000..245e5116a3
--- /dev/null
+++ b/libavutil/motion_vector.h
@@ -0,0 +1,50 @@
+/*
+ * 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
+ */
+
+#ifndef AVUTIL_MOTION_VECTOR_H
+#define AVUTIL_MOTION_VECTOR_H
+
+#include <stdint.h>
+
+typedef struct AVMotionVector {
+    /**
+     * Where the current macroblock comes from; negative value when it comes
+     * from the past, positive value when it comes from the future.
+     * XXX: set exact relative ref frame reference instead of a +/- 1 "direction".
+     */
+    int32_t source;
+    /**
+     * Width and height of the block.
+     */
+    uint8_t w, h;
+    /**
+     * Absolute source position.
+     */
+    uint16_t src_x, src_y;
+    /**
+     * Absolute destination position.
+     */
+    uint16_t dst_x, dst_y;
+    /**
+     * Extra flag information.
+     * Currently unused.
+     */
+    uint64_t flags;
+} AVMotionVector;
+
+#endif /* AVUTIL_MOTION_VECTOR_H */