avutil: introduce AVAmbientViewingEnvironment side data

This enables exposing H.274 Ambient Viewing Environment
metadata in the framework.

doc/APIchanges

@@ -14,6 +14,12 @@ libavutil:     2021-04-27
 
 API changes, most recent first:
 
+2023-01-13 - xxxxxxxxxx - lavu 57.44.100 - ambient_viewing_environment.h frame.h
+  Adds a new structure for holding H.274 Ambient Viewing Environment metadata,
+  AVAmbientViewingEnvironment.
+  Adds a new AVFrameSideDataType entry AV_FRAME_DATA_AMBIENT_VIEWING_ENVIRONMENT
+  for it.
+
 2022-12-xx - xxxxxxxxxx - lavc 59.55.100 - avcodec.h
   Add AV_HWACCEL_FLAG_UNSAFE_OUTPUT.
 

libavutil/Makefile

@@ -4,6 +4,7 @@ DESC = FFmpeg utility library
 HEADERS = adler32.h                                                     \
           aes.h                                                         \
           aes_ctr.h                                                     \
+          ambient_viewing_environment.h                                 \
           attributes.h                                                  \
           audio_fifo.h                                                  \
           avassert.h                                                    \
@@ -102,6 +103,7 @@ BUILT_HEADERS = avconfig.h                                              \
 OBJS = adler32.o                                                        \
        aes.o                                                            \
        aes_ctr.o                                                        \
+       ambient_viewing_environment.o                                    \
        audio_fifo.o                                                     \
        avstring.o                                                       \
        avsscanf.o                                                       \

libavutil/ambient_viewing_environment.c

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2023 Jan Ekström <jeebjp@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
+ */
+
+#include "ambient_viewing_environment.h"
+#include "mem.h"
+
+AVAmbientViewingEnvironment *av_ambient_viewing_environment_alloc(size_t *size)
+{
+    AVAmbientViewingEnvironment *env =
+        av_mallocz(sizeof(AVAmbientViewingEnvironment));
+    if (!env)
+        return NULL;
+
+     if (size)
+        *size = sizeof(*env);
+
+    return env;
+}
+
+AVAmbientViewingEnvironment *av_ambient_viewing_environment_create_side_data(AVFrame *frame)
+{
+    AVFrameSideData *side_data =
+        av_frame_new_side_data(frame,
+                               AV_FRAME_DATA_AMBIENT_VIEWING_ENVIRONMENT,
+                               sizeof(AVAmbientViewingEnvironment));
+    if (!side_data)
+        return NULL;
+
+    memset(side_data->data, 0, side_data->size);
+
+    return (AVAmbientViewingEnvironment *)side_data->data;
+}

libavutil/ambient_viewing_environment.h

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2023 Jan Ekström <jeebjp@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
+ */
+
+#ifndef AVUTIL_AMBIENT_VIEWING_ENVIRONMENT_H
+#define AVUTIL_AMBIENT_VIEWING_ENVIRONMENT_H
+
+#include <stddef.h>
+#include "frame.h"
+#include "rational.h"
+
+/**
+ * Ambient viewing environment metadata as defined by H.274. The values are
+ * saved in AVRationals so that they keep their exactness, while allowing for
+ * easy access to a double value with f.ex. av_q2d.
+ *
+ * @note sizeof(AVAmbientViewingEnvironment) is not part of the public ABI, and
+ *       it must be allocated using av_ambient_viewing_environment_alloc.
+ */
+typedef struct AVAmbientViewingEnvironment {
+    /**
+     * Environmental illuminance of the ambient viewing environment in lux.
+     */
+    AVRational ambient_illuminance;
+
+    /**
+     * Normalized x chromaticity coordinate of the environmental ambient light
+     * in the nominal viewing environment according to the CIE 1931 definition
+     * of x and y as specified in ISO/CIE 11664-1.
+     */
+    AVRational ambient_light_x;
+
+    /**
+     * Normalized y chromaticity coordinate of the environmental ambient light
+     * in the nominal viewing environment according to the CIE 1931 definition
+     * of x and y as specified in ISO/CIE 11664-1.
+     */
+    AVRational ambient_light_y;
+} AVAmbientViewingEnvironment;
+
+/**
+ * Allocate an AVAmbientViewingEnvironment structure.
+ *
+ * @return the newly allocated struct or NULL on failure
+ */
+AVAmbientViewingEnvironment *av_ambient_viewing_environment_alloc(size_t *size);
+
+/**
+ * Allocate and add an AVAmbientViewingEnvironment structure to an existing
+ * AVFrame as side data.
+ *
+ * @return the newly allocated struct, or NULL on failure
+ */
+AVAmbientViewingEnvironment *av_ambient_viewing_environment_create_side_data(AVFrame *frame);
+
+#endif /* AVUTIL_AMBIENT_VIEWING_ENVIRONMENT_H */

libavutil/frame.c

@@ -831,6 +831,7 @@ const char *av_frame_side_data_name(enum AVFrameSideDataType type)
     case AV_FRAME_DATA_DETECTION_BBOXES:            return "Bounding boxes for object detection and classification";
     case AV_FRAME_DATA_DOVI_RPU_BUFFER:             return "Dolby Vision RPU Data";
     case AV_FRAME_DATA_DOVI_METADATA:               return "Dolby Vision Metadata";
+    case AV_FRAME_DATA_AMBIENT_VIEWING_ENVIRONMENT: return "Ambient viewing environment";
     }
     return NULL;
 }

libavutil/frame.h

@@ -209,6 +209,11 @@ enum AVFrameSideDataType {
      * volume transform - CUVA 005.1-2021.
      */
     AV_FRAME_DATA_DYNAMIC_HDR_VIVID,
+
+    /**
+     * Ambient viewing environment metadata, as defined by H.274.
+     */
+    AV_FRAME_DATA_AMBIENT_VIEWING_ENVIRONMENT,
 };
 
 enum AVActiveFormatDescription {

libavutil/version.h

@@ -79,7 +79,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR  57
-#define LIBAVUTIL_VERSION_MINOR  43
+#define LIBAVUTIL_VERSION_MINOR  44
 #define LIBAVUTIL_VERSION_MICRO 100
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \