diff --git a/libavutil/frame.c b/libavutil/frame.c
index ef1613c344..d9bd19b2aa 100644
--- a/libavutil/frame.c
+++ b/libavutil/frame.c
@@ -799,12 +799,34 @@ AVFrameSideData *av_frame_side_data_new(AVFrameSideData ***sd, int *nb_sd,
                                         enum AVFrameSideDataType type,
                                         size_t size, unsigned int flags)
 {
-    AVBufferRef     *buf = av_buffer_alloc(size);
+    const AVSideDataDescriptor *desc = av_frame_side_data_desc(type);
+    AVBufferRef     *buf;
     AVFrameSideData *ret = NULL;
 
     if (flags & AV_FRAME_SIDE_DATA_FLAG_UNIQUE)
         remove_side_data(sd, nb_sd, type);
+    if (!desc || !(desc->props & AV_SIDE_DATA_PROP_MULTI)) {
+        for (int i = 0; i < *nb_sd; i++) {
+            AVFrameSideData *entry = ((*sd)[i]);
+            if (entry->type != type)
+                continue;
+            if (!(flags & AV_FRAME_SIDE_DATA_FLAG_REPLACE))
+                return NULL;
+
+            buf = av_buffer_alloc(size);
+            if (!buf)
+                return NULL;
+
+            av_buffer_unref(&entry->buf);
+            av_dict_free(&entry->metadata);
+            entry->buf  = buf;
+            entry->data = buf->data;
+            entry->size = buf->size;
+            return entry;
+        }
+    }
 
+    buf = av_buffer_alloc(size);
     ret = add_side_data_from_buf(sd, nb_sd, type, buf);
     if (!ret)
         av_buffer_unref(&buf);
@@ -815,6 +837,7 @@ AVFrameSideData *av_frame_side_data_new(AVFrameSideData ***sd, int *nb_sd,
 int av_frame_side_data_clone(AVFrameSideData ***sd, int *nb_sd,
                              const AVFrameSideData *src, unsigned int flags)
 {
+    const AVSideDataDescriptor *desc;
     AVBufferRef     *buf    = NULL;
     AVFrameSideData *sd_dst = NULL;
     int              ret    = AVERROR_BUG;
@@ -822,13 +845,41 @@ int av_frame_side_data_clone(AVFrameSideData ***sd, int *nb_sd,
     if (!sd || !src || !nb_sd || (*nb_sd && !*sd))
         return AVERROR(EINVAL);
 
+    desc = av_frame_side_data_desc(src->type);
+    if (flags & AV_FRAME_SIDE_DATA_FLAG_UNIQUE)
+        remove_side_data(sd, nb_sd, src->type);
+    if (!desc || !(desc->props & AV_SIDE_DATA_PROP_MULTI)) {
+        for (int i = 0; i < *nb_sd; i++) {
+            AVFrameSideData *entry = ((*sd)[i]);
+            AVDictionary *dict = NULL;
+
+            if (entry->type != src->type)
+                continue;
+            if (!(flags & AV_FRAME_SIDE_DATA_FLAG_REPLACE))
+                return AVERROR(EEXIST);
+
+            ret = av_dict_copy(&dict, src->metadata, 0);
+            if (ret < 0)
+                return ret;
+
+            ret = av_buffer_replace(&entry->buf, src->buf);
+            if (ret < 0) {
+                av_dict_free(&dict);
+                return ret;
+            }
+
+            av_dict_free(&entry->metadata);
+            entry->metadata = dict;
+            entry->data     = src->data;
+            entry->size     = src->size;
+            return 0;
+        }
+    }
+
     buf = av_buffer_ref(src->buf);
     if (!buf)
         return AVERROR(ENOMEM);
 
-    if (flags & AV_FRAME_SIDE_DATA_FLAG_UNIQUE)
-        remove_side_data(sd, nb_sd, src->type);
-
     sd_dst = add_side_data_from_buf(sd, nb_sd, src->type, buf);
     if (!sd_dst) {
         av_buffer_unref(&buf);
diff --git a/libavutil/frame.h b/libavutil/frame.h
index 3b6d746a16..2ea129888e 100644
--- a/libavutil/frame.h
+++ b/libavutil/frame.h
@@ -1040,7 +1040,14 @@ const AVSideDataDescriptor *av_frame_side_data_desc(enum AVFrameSideDataType typ
  */
 void av_frame_side_data_free(AVFrameSideData ***sd, int *nb_sd);
 
+/**
+ * Remove existing entries before adding new ones.
+ */
 #define AV_FRAME_SIDE_DATA_FLAG_UNIQUE (1 << 0)
+/**
+ * Don't add a new entry if another of the same type exists.
+ */
+#define AV_FRAME_SIDE_DATA_FLAG_REPLACE (1 << 1)
 
 /**
  * Add new side data entry to an array.
@@ -1053,10 +1060,12 @@ void av_frame_side_data_free(AVFrameSideData ***sd, int *nb_sd);
  * @param size  size of the side data
  * @param flags Some combination of AV_FRAME_SIDE_DATA_FLAG_* flags, or 0.
  *
- * @return newly added side data on success, NULL on error. In case of
- *         AV_FRAME_SIDE_DATA_FLAG_UNIQUE being set, entries of matching
- *         AVFrameSideDataType will be removed before the addition is
- *         attempted.
+ * @return newly added side data on success, NULL on error.
+ * @note In case of AV_FRAME_SIDE_DATA_FLAG_UNIQUE being set, entries of
+ *       matching AVFrameSideDataType will be removed before the addition
+ *       is attempted.
+ * @note In case of AV_FRAME_SIDE_DATA_FLAG_REPLACE being set, if an
+ *       entry of the same type already exists, it will be replaced instead.
  */
 AVFrameSideData *av_frame_side_data_new(AVFrameSideData ***sd, int *nb_sd,
                                         enum AVFrameSideDataType type,
@@ -1074,10 +1083,12 @@ AVFrameSideData *av_frame_side_data_new(AVFrameSideData ***sd, int *nb_sd,
  *              for the buffer.
  * @param flags Some combination of AV_FRAME_SIDE_DATA_FLAG_* flags, or 0.
  *
- * @return negative error code on failure, >=0 on success. In case of
- *         AV_FRAME_SIDE_DATA_FLAG_UNIQUE being set, entries of matching
- *         AVFrameSideDataType will be removed before the addition is
- *         attempted.
+ * @return negative error code on failure, >=0 on success.
+ * @note In case of AV_FRAME_SIDE_DATA_FLAG_UNIQUE being set, entries of
+ *       matching AVFrameSideDataType will be removed before the addition
+ *       is attempted.
+ * @note In case of AV_FRAME_SIDE_DATA_FLAG_REPLACE being set, if an
+ *       entry of the same type already exists, it will be replaced instead.
  */
 int av_frame_side_data_clone(AVFrameSideData ***sd, int *nb_sd,
                              const AVFrameSideData *src, unsigned int flags);
diff --git a/libavutil/tests/side_data_array.c b/libavutil/tests/side_data_array.c
index 793a62c009..633e9ee681 100644
--- a/libavutil/tests/side_data_array.c
+++ b/libavutil/tests/side_data_array.c
@@ -20,23 +20,22 @@
 
 #include <stdio.h>
 #include "libavutil/frame.c"
-#include "libavutil/mastering_display_metadata.h"
+#include "libavutil/internal.h"
 
-static void print_clls(const AVFrameSideData **sd, const int nb_sd)
+static void print_entries(const AVFrameSideData **sd, const int nb_sd)
 {
     for (int i = 0; i < nb_sd; i++) {
         const AVFrameSideData *entry = sd[i];
 
-        printf("sd %d, %s",
-               i, av_frame_side_data_name(entry->type));
+        printf("sd %d (size %"SIZE_SPECIFIER"), %s",
+               i, entry->size, av_frame_side_data_name(entry->type));
 
-        if (entry->type != AV_FRAME_DATA_CONTENT_LIGHT_LEVEL) {
+        if (entry->type != AV_FRAME_DATA_SEI_UNREGISTERED) {
             putchar('\n');
             continue;
         }
 
-        printf(": MaxCLL: %u\n",
-               ((AVContentLightMetadata *)entry->data)->MaxCLL);
+        printf(": %d\n", *(int32_t *)entry->data);
     }
 }
 
@@ -51,51 +50,60 @@ int main(void)
 
     av_assert0(
         av_frame_side_data_new(&set.sd, &set.nb_sd,
-                               AV_FRAME_DATA_AMBIENT_VIEWING_ENVIRONMENT,
-                               0, 0));
+                               AV_FRAME_DATA_CONTENT_LIGHT_LEVEL,
+                               sizeof(int64_t), 0));
+    av_assert0(
+        av_frame_side_data_new(&set.sd, &set.nb_sd,
+                               AV_FRAME_DATA_CONTENT_LIGHT_LEVEL,
+                               sizeof(int32_t), AV_FRAME_SIDE_DATA_FLAG_REPLACE));
 
     // test entries in the middle
     for (int value = 1; value < 4; value++) {
         AVFrameSideData *sd = av_frame_side_data_new(
-            &set.sd, &set.nb_sd, AV_FRAME_DATA_CONTENT_LIGHT_LEVEL,
-            sizeof(AVContentLightMetadata), 0);
+            &set.sd, &set.nb_sd, AV_FRAME_DATA_SEI_UNREGISTERED,
+            sizeof(int32_t), 0);
 
         av_assert0(sd);
 
-        ((AVContentLightMetadata *)sd->data)->MaxCLL = value;
+        *(int32_t *)sd->data = value;
     }
 
     av_assert0(
         av_frame_side_data_new(
-            &set.sd, &set.nb_sd, AV_FRAME_DATA_SPHERICAL, 0, 0));
+            &set.sd, &set.nb_sd, AV_FRAME_DATA_SPHERICAL,
+           sizeof(int64_t), 0));
+
+    av_assert0(
+        av_frame_side_data_new(
+            &set.sd, &set.nb_sd, AV_FRAME_DATA_SPHERICAL,
+            sizeof(int32_t), AV_FRAME_SIDE_DATA_FLAG_REPLACE));
 
     // test entries at the end
     for (int value = 1; value < 4; value++) {
         AVFrameSideData *sd = av_frame_side_data_new(
-            &set.sd, &set.nb_sd, AV_FRAME_DATA_CONTENT_LIGHT_LEVEL,
-            sizeof(AVContentLightMetadata), 0);
+            &set.sd, &set.nb_sd, AV_FRAME_DATA_SEI_UNREGISTERED,
+            sizeof(int32_t), 0);
 
         av_assert0(sd);
 
-        ((AVContentLightMetadata *)sd->data)->MaxCLL = value + 3;
+        *(int32_t *)sd->data = value + 3;
     }
 
     puts("Initial addition results with duplicates:");
-    print_clls((const AVFrameSideData **)set.sd, set.nb_sd);
+    print_entries((const AVFrameSideData **)set.sd, set.nb_sd);
 
     {
         AVFrameSideData *sd = av_frame_side_data_new(
-            &set.sd, &set.nb_sd, AV_FRAME_DATA_CONTENT_LIGHT_LEVEL,
-            sizeof(AVContentLightMetadata),
-            AV_FRAME_SIDE_DATA_FLAG_UNIQUE);
+            &set.sd, &set.nb_sd, AV_FRAME_DATA_SEI_UNREGISTERED,
+            sizeof(int32_t), AV_FRAME_SIDE_DATA_FLAG_UNIQUE);
 
         av_assert0(sd);
 
-        ((AVContentLightMetadata *)sd->data)->MaxCLL = 1337;
+        *(int32_t *)sd->data = 1337;
     }
 
     puts("\nFinal state after a single 'no-duplicates' addition:");
-    print_clls((const AVFrameSideData **)set.sd, set.nb_sd);
+    print_entries((const AVFrameSideData **)set.sd, set.nb_sd);
 
     av_frame_side_data_free(&set.sd, &set.nb_sd);
 
diff --git a/tests/ref/fate/side_data_array b/tests/ref/fate/side_data_array
index 7d8c684d8f..c1d77b0445 100644
--- a/tests/ref/fate/side_data_array
+++ b/tests/ref/fate/side_data_array
@@ -1,14 +1,14 @@
 Initial addition results with duplicates:
-sd 0, Ambient viewing environment
-sd 1, Content light level metadata: MaxCLL: 1
-sd 2, Content light level metadata: MaxCLL: 2
-sd 3, Content light level metadata: MaxCLL: 3
-sd 4, Spherical Mapping
-sd 5, Content light level metadata: MaxCLL: 4
-sd 6, Content light level metadata: MaxCLL: 5
-sd 7, Content light level metadata: MaxCLL: 6
+sd 0 (size 4), Content light level metadata
+sd 1 (size 4), H.26[45] User Data Unregistered SEI message: 1
+sd 2 (size 4), H.26[45] User Data Unregistered SEI message: 2
+sd 3 (size 4), H.26[45] User Data Unregistered SEI message: 3
+sd 4 (size 4), Spherical Mapping
+sd 5 (size 4), H.26[45] User Data Unregistered SEI message: 4
+sd 6 (size 4), H.26[45] User Data Unregistered SEI message: 5
+sd 7 (size 4), H.26[45] User Data Unregistered SEI message: 6
 
 Final state after a single 'no-duplicates' addition:
-sd 0, Ambient viewing environment
-sd 1, Spherical Mapping
-sd 2, Content light level metadata: MaxCLL: 1337
+sd 0 (size 4), Content light level metadata
+sd 1 (size 4), Spherical Mapping
+sd 2 (size 4), H.26[45] User Data Unregistered SEI message: 1337
