lavu: Add AVSphericalMapping type and frame side data

While no decoder currently exports spherical information, this type
represents a frame property that has to be passed through from container
to frames.

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>

1 files changed, 137 insertions, 0 deletions

diff --git a/libavutil/spherical.h b/libavutil/spherical.h
new file mode 100644
index 0000000000..0a669da83a
--- /dev/null
+++ b/libavutil/spherical.h
@@ -0,0 +1,137 @@
+/*
+ * Copyright (c) 2016 Vittorio Giovara <vittorio.giovara@gmail.com>
+ *
+ * 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
+ * Spherical video
+ */
+
+#ifndef AVUTIL_SPHERICAL_H
+#define AVUTIL_SPHERICAL_H
+
+/**
+ * @addtogroup lavu_video
+ * @{
+ *
+ * @defgroup lavu_video_spherical Spherical video mapping
+ * @{
+ */
+
+/**
+ * @addtogroup lavu_video_spherical
+ * A spherical video file contains surfaces that need to be mapped onto a
+ * sphere. Depending on how the frame was converted, a different distortion
+ * transformation or surface recomposition function needs to be applied before
+ * the video should be mapped and displayed.
+ */
+
+/**
+ * Projection of the video surface(s) on a sphere.
+ */
+enum AVSphericalProjection {
+    /**
+     * Video represents a sphere mapped on a flat surface using
+     * equirectangular projection.
+     */
+    AV_SPHERICAL_EQUIRECTANGULAR,
+
+    /**
+     * Video frame is split into 6 faces of a cube, and arranged on a
+     * 3x2 layout. Faces are oriented upwards for the front, left, right,
+     * and back faces. The up face is oriented so the top of the face is
+     * forwards and the down face is oriented so the top of the face is
+     * to the back.
+     */
+    AV_SPHERICAL_CUBEMAP,
+};
+
+/**
+ * This structure describes how to handle spherical videos, outlining
+ * information about projection, initial layout, and any other view modifier.
+ *
+ * @note The struct must be allocated with av_spherical_alloc() and
+ *       its size is not a part of the public ABI.
+ */
+typedef struct AVSphericalMapping {
+    /**
+     * Projection type.
+     */
+    enum AVSphericalProjection projection;
+
+    /**
+     * @name Initial orientation
+     * @{
+     * There fields describe additional rotations applied to the sphere after
+     * the video frame is mapped onto it. The sphere is rotated around the
+     * viewer, who remains stationary. The order of transformation is always
+     * yaw, followed by pitch, and finally by roll.
+     *
+     * The coordinate system matches the one defined in OpenGL, where the
+     * forward vector (z) is coming out of screen, and it is equivalent to
+     * a rotation matrix of R = r_y(yaw) * r_x(pitch) * r_z(roll).
+     *
+     * A positive yaw rotates the portion of the sphere in front of the viewer
+     * toward their right. A positive pitch rotates the portion of the sphere
+     * in front of the viewer upwards. A positive roll tilts the portion of
+     * the sphere in front of the viewer to the viewer's right.
+     *
+     * These values are exported as 16.16 fixed point.
+     *
+     * See this equirectangular projection as example:
+     *
+     * @code{.unparsed}
+     *                   Yaw
+     *     -180           0           180
+     *   90 +-------------+-------------+  180
+     *      |             |             |                  up
+     * P    |             |             |                 y|    forward
+     * i    |             ^             |                  |   /z
+     * t  0 +-------------X-------------+    0 Roll        |  /
+     * c    |             |             |                  | /
+     * h    |             |             |                 0|/_____right
+     *      |             |             |                        x
+     *  -90 +-------------+-------------+ -180
+     *
+     * X - the default camera center
+     * ^ - the default up vector
+     * @endcode
+     */
+    int32_t yaw;   ///< Rotation around the up vector [-180, 180].
+    int32_t pitch; ///< Rotation around the right vector [-90, 90].
+    int32_t roll;  ///< Rotation around the forward vector [-180, 180].
+    /**
+     * @}
+     */
+} AVSphericalMapping;
+
+/**
+ * Allocate a AVSphericalVideo structure and initialize its fields to default
+ * values.
+ *
+ * @return the newly allocated struct or NULL on failure
+ */
+AVSphericalMapping *av_spherical_alloc(size_t *size);
+
+/**
+ * @}
+ * @}
+ */
+
+#endif /* AVUTIL_SPHERICAL_H */