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>

1 files changed, 64 insertions, 0 deletions

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;
+}