[FFmpeg-devel] [PATCH v2 1/6] avutil: add an API to handle Three Dimensional Reference Displays Information

[James Almer <jamrial@gmail.com>]

As defined in section G.14.3.2.3 of ITU-T H.265, it's required for proper
signaling of MV-HEVC.

Signed-off-by: James Almer <jamrial@gmail.com>
---
Better namespace, and now only allocating the required display reference entries.

 libavutil/Makefile            |   2 +
 libavutil/ref_displays_info.c |  53 +++++++++++
 libavutil/ref_displays_info.h | 169 ++++++++++++++++++++++++++++++++++
 3 files changed, 224 insertions(+)
 create mode 100644 libavutil/ref_displays_info.c
 create mode 100644 libavutil/ref_displays_info.h

diff --git a/libavutil/Makefile b/libavutil/Makefile
index f8031815bd..67e942243e 100644
--- a/libavutil/Makefile
+++ b/libavutil/Makefile
@@ -76,6 +76,7 @@ HEADERS = adler32.h                                                     \
           random_seed.h                                                 \
           rc4.h                                                         \
           rational.h                                                    \
+          ref_displays_info.h                                           \
           refstruct.h                                                   \
           replaygain.h                                                  \
           ripemd.h                                                      \
@@ -166,6 +167,7 @@ OBJS = adler32.o                                                        \
        pixelutils.o                                                     \
        random_seed.o                                                    \
        rational.o                                                       \
+       ref_displays_info.o                                              \
        refstruct.o                                                      \
        reverse.o                                                        \
        rc4.o                                                            \
diff --git a/libavutil/ref_displays_info.c b/libavutil/ref_displays_info.c
new file mode 100644
index 0000000000..a51aa42b54
--- /dev/null
+++ b/libavutil/ref_displays_info.c
@@ -0,0 +1,53 @@
+/*
+ * 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
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "avassert.h"
+#include "mem.h"
+#include "ref_displays_info.h"
+
+AV3DReferenceDisplaysInfo *av_ref_displays_info_alloc(unsigned int num_ref_displays,
+                                                      size_t *out_size)
+{
+    struct CombinedStruct {
+        AV3DReferenceDisplaysInfo i;
+        AV3DReferenceDisplay      r;
+    };
+    const size_t ref_offset = offsetof(struct CombinedStruct, r);
+    size_t size = ref_offset;
+    AV3DReferenceDisplaysInfo *rdi;
+
+    if (num_ref_displays > (SIZE_MAX - size) / sizeof(AV3DReferenceDisplay))
+        return NULL;
+    size += sizeof(AV3DReferenceDisplay) * num_ref_displays;
+
+    rdi = av_mallocz(size);
+    if (!rdi)
+        return NULL;
+
+    rdi->num_ref_displays = num_ref_displays;
+    rdi->ref_size         = sizeof(AV3DReferenceDisplay);
+    rdi->ref_offset       = ref_offset;
+
+    if (out_size)
+        *out_size = size;
+
+    return rdi;
+}
diff --git a/libavutil/ref_displays_info.h b/libavutil/ref_displays_info.h
new file mode 100644
index 0000000000..02ff4fcd98
--- /dev/null
+++ b/libavutil/ref_displays_info.h
@@ -0,0 +1,169 @@
+/*
+ * 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
+ * @ingroup lavu_video_3d_reference_displays_info
+ * 3D Reference Displays Information
+ */
+
+#ifndef AVUTIL_REF_DISPLAYS_INFO_H
+#define AVUTIL_REF_DISPLAYS_INFO_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "libavutil/avassert.h"
+
+/**
+ * @defgroup lavu_video_3d_reference_displays_info 3D Reference Displays Information
+ * @ingroup lavu_video
+ *
+ * The 3D Reference Displays Information describes information about the reference display
+ * width(s) and reference viewing distance(s) as well as information about the corresponding
+ * reference stereo pair(s).
+ * @{
+ */
+
+/**
+ * This structure describes information about the reference display width(s) and reference
+ * viewing distance(s) as well as information about the corresponding reference stereo pair(s).
+ * See section G.14.3.2.3 of ITU-T H.265 for more information.
+ *
+ * @note The struct must be allocated with av_ref_displays_info_alloc() and its size is not a
+ *       part of the public ABI.
+ */
+typedef struct AV3DReferenceDisplaysInfo {
+    /**
+     * The number of reference displays that are signalled in this struct.
+     * Allowed range is 1 to 32, inclusive.
+     */
+    unsigned int num_ref_displays;
+
+    /**
+     * Offset in bytes from the beginning of this structure at which the array
+     * of reference displays starts.
+     */
+    size_t ref_offset;
+
+    /**
+     * Size of each reference display entry in bytes. May not match sizeof(AV3DReferenceDisplay).
+     */
+    size_t ref_size;
+
+    /**
+     * The exponent of the maximum allowable truncation error for
+     * {exponent,mantissa}_ref_display_width as given by 2<sup>(-prec_ref_display_width)</sup>.
+     */
+    uint8_t prec_ref_display_width;
+
+    /**
+     * A flag to indicate the presence of reference viewing distance.
+     * If false, the values of prec_ref_viewing_dist, exponent_ref_viewing_distance,
+     * and mantissa_ref_viewing_distance are undefined.
+     */
+    uint8_t ref_viewing_distance_flag;
+
+    /**
+     * The exponent of the maximum allowable truncation error for
+     * {exponent,mantissa}_ref_viewing_distance as given by 2<sup>^(-prec_ref_viewing_dist)</sup>.
+     * The value of prec_ref_viewing_dist shall be in the range of 0 to 31, inclusive.
+     */
+    uint8_t prec_ref_viewing_dist;
+} AV3DReferenceDisplaysInfo;
+
+/**
+ * Data structure for storing a reference display information.
+ * It is allocated as a part of AV3DReferenceDisplaysInfo and should be retrieved with
+ * av_ref_displays_info_display().
+ *
+ * sizeof(AV3DReferenceDisplay) is not a part of the ABI and new fields may be
+ * added to it.
+ */
+typedef struct AV3DReferenceDisplay {
+    /**
+     * The ViewId of the left view of a stereo pair corresponding to the n-th reference display.
+     */
+    uint16_t left_view_id;
+
+    /**
+     * The ViewId of the left view of a stereo pair corresponding to the n-th reference display.
+     */
+    uint16_t right_view_id;
+
+    /**
+     * The exponent part of the reference display width of the n-th reference display.
+     */
+    uint8_t exponent_ref_display_width;
+
+    /**
+     * The mantissa part of the reference display width of the n-th reference display.
+     */
+    uint8_t mantissa_ref_display_width;
+
+    /**
+     * Tthe exponent part of the reference viewing distance of the n-th reference display.
+     */
+    uint8_t exponent_ref_viewing_distance;
+
+    /**
+     * The mantissa part of the reference viewing distance of the n-th reference display.
+     */
+    uint8_t mantissa_ref_viewing_distance;
+
+    /**
+     * An array of flags to indicates that the information about additional horizontal shift of
+     * the left and right views for the n-th reference display is present.
+     */
+    uint8_t additional_shift_present_flag;
+
+    /**
+     * The recommended additional horizontal shift for a stereo pair corresponding to the n-th
+     * reference baseline and the n-th reference display.
+     */
+    int16_t num_sample_shift;
+} AV3DReferenceDisplay;
+
+/**
+ * Get the reference display at the specified {@code idx}.
+ * Must be between 0 and num_ref_displays - 1.
+ */
+static av_always_inline AV3DReferenceDisplay*
+av_ref_displays_info_display(AV3DReferenceDisplaysInfo *rdi, unsigned int idx)
+{
+    av_assert0(idx < rdi->num_ref_displays);
+    return (AV3DReferenceDisplay *)((uint8_t *)rdi + rdi->ref_offset +
+                                    idx * rdi->ref_size);
+}
+
+/**
+ * Allocates memory for AV3DReferenceDisplaysInfo, plus an array of
+ * {@code num_ref_displays} AV3DReferenceDisplay and initializes the variables.
+ * Can be freed with a normal av_free() call.
+ *
+ * @param num_ref_displays the number of reference displays.
+ * @return the newly allocated struct or NULL on failure
+ */
+AV3DReferenceDisplaysInfo *av_ref_displays_info_alloc(unsigned int num_ref_displays,
+                                                      size_t *out_size);
+
+/**
+ * @}
+ */
+
+#endif /* AVUTIL_REF_DISPLAYS_INFO_H */
-- 
2.48.1

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