Add transformation matrix API.

Add AV_PKT_DATA_DISPLAYMATRIX and AV_FRAME_DATA_DISPLAYMATRIX as stream and
frame side data (respectively) to describe a display transformation matrix
for linear transformation operations on the decoded video.

Add functions to easily extract a rotation angle from a matrix and
conversely to setup a matrix for a given rotation angle.

Signed-off-by: Anton Khirnov <anton@khirnov.net>

5 files changed, 152 insertions, 1 deletions

diff --git a/libavutil/Makefile b/libavutil/Makefile
index d5c1636840..0f8ed08d61 100644
--- a/libavutil/Makefile
+++ b/libavutil/Makefile
@@ -16,6 +16,7 @@ HEADERS = adler32.h                                                     \
           common.h                                                      \
           cpu.h                                                         \
           crc.h                                                         \
+          display.h                                                     \
           downmix_info.h                                                \
           error.h                                                       \
           eval.h                                                        \
@@ -69,6 +70,7 @@ OBJS = adler32.o                                                        \
        cpu.o                                                            \
        crc.o                                                            \
        des.o                                                            \
+       display.o                                                        \
        downmix_info.o                                                   \
        error.o                                                          \
        eval.o                                                           \
diff --git a/libavutil/display.c b/libavutil/display.c
new file mode 100644
index 0000000000..ae6c1c2474
--- /dev/null
+++ b/libavutil/display.c
@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2014 Vittorio Giovara <vittorio.giovara@gmail.com>
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdint.h>
+#include <string.h>
+#include <math.h>
+
+#include "display.h"
+
+// fixed point to double
+#define CONV_FP(x) ((double) (x)) / (1 << 16)
+
+// double to fixed point
+#define CONV_DB(x) (int32_t) ((x) * (1 << 16))
+
+double av_display_rotation_get(const int32_t matrix[9])
+{
+    double rotation, scale[2];
+
+    scale[0] = sqrt(CONV_FP(matrix[0]) * CONV_FP(matrix[0]) +
+                    CONV_FP(matrix[3]) * CONV_FP(matrix[3]));
+    scale[1] = sqrt(CONV_FP(matrix[1]) * CONV_FP(matrix[1]) +
+                    CONV_FP(matrix[4]) * CONV_FP(matrix[4]));
+
+    if (scale[0] == 0.0 || scale[1] == 0.0)
+        return NAN;
+
+    rotation = atan2(CONV_FP(matrix[1]) / scale[1],
+                     CONV_FP(matrix[0]) / scale[0]) * 180 / M_PI;
+
+    return rotation;
+}
+
+void av_display_rotation_set(int32_t matrix[9], double angle)
+{
+    double radians = angle * M_PI / 180.0f;
+    double c = cos(radians);
+    double s = sin(radians);
+
+    memset(matrix, 0, 9 * sizeof(int32_t));
+
+    matrix[0] = CONV_DB(c);
+    matrix[1] = CONV_DB(-s);
+    matrix[3] = CONV_DB(s);
+    matrix[4] = CONV_DB(c);
+    matrix[8] = 1 << 30;
+}
diff --git a/libavutil/display.h b/libavutil/display.h
new file mode 100644
index 0000000000..ea762a4249
--- /dev/null
+++ b/libavutil/display.h
@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2014 Vittorio Giovara <vittorio.giovara@gmail.com>
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_DISPLAY_H
+#define AVUTIL_DISPLAY_H
+
+#include <stdint.h>
+
+/**
+ * The display transformation matrix specifies an affine transformation that
+ * should be applied to video frames for correct presentation. It is compatible
+ * with the matrices stored in the ISO/IEC 14496-12 container format.
+ *
+ * The data is a 3x3 matrix represented as a 9-element array:
+ *
+ *                                  | a b u |
+ *   (a, b, u, c, d, v, x, y, w) -> | c d v |
+ *                                  | x y w |
+ *
+ * All numbers are stored in native endianness, as 16.16 fixed-point values,
+ * except for u, v and w, which are stored as 2.30 fixed-point values.
+ *
+ * The transformation maps a point (p, q) in the source (pre-transformation)
+ * frame to the point (p', q') in the destination (post-transformation) frame as
+ * follows:
+ *               | a b u |
+ *   (p, q, 1) . | c d v | = z * (p', q', 1)
+ *               | x y w |
+ *
+ * The transformation can also be more explicitly written in components as
+ * follows:
+ *   p' = (a * p + c * q + x) / z;
+ *   q' = (b * p + d * q + y) / z;
+ *   z  =  u * p + v * q + w
+ */
+
+/**
+ * Extract the rotation component of the transformation matrix.
+ *
+ * @param matrix the transformation matrix
+ * @return the angle (in degrees) by which the transformation rotates the frame.
+ *         The angle will be in range [-180.0, 180.0], or NaN if the matrix is
+ *         singular.
+ *
+ * @note floating point numbers are inherently inexact, so callers are
+ *       recommended to round the return value to nearest integer before use.
+ */
+double av_display_rotation_get(const int32_t matrix[9]);
+
+/**
+ * Initialize a transformation matrix describing a pure rotation by the
+ * specified angle (in degrees).
+ *
+ * @param matrix an allocated transformation matrix (will be fully overwritten
+ *               by this function)
+ * @param angle rotation angle in degrees.
+ */
+void av_display_rotation_set(int32_t matrix[9], double angle);
+
+#endif /* AVUTIL_DISPLAY_H */
diff --git a/libavutil/frame.h b/libavutil/frame.h
index 3bec8e5948..958cd26975 100644
--- a/libavutil/frame.h
+++ b/libavutil/frame.h
@@ -73,6 +73,14 @@ enum AVFrameSideDataType {
      * ReplayGain information in the form of the AVReplayGain struct.
      */
     AV_FRAME_DATA_REPLAYGAIN,
+    /**
+     * This side data contains a 3x3 transformation matrix describing an affine
+     * transformation that needs to be applied to the frame for correct
+     * presentation.
+     *
+     * See libavutil/display.h for a detailed description of the data.
+     */
+    AV_FRAME_DATA_DISPLAYMATRIX,
 };
 
 typedef struct AVFrameSideData {
diff --git a/libavutil/version.h b/libavutil/version.h
index 43e7947121..f35dabcfbe 100644
--- a/libavutil/version.h
+++ b/libavutil/version.h
@@ -54,7 +54,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR 53
-#define LIBAVUTIL_VERSION_MINOR 14
+#define LIBAVUTIL_VERSION_MINOR 15
 #define LIBAVUTIL_VERSION_MICRO  0
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \