[FFmpeg-devel] avformat/matroska: Support HDR10+ metadata in Matroska.

diff --git a/libavcodec/dynamic_hdr10_plus.c b/libavcodec/dynamic_hdr10_plus.c
index 34a44aac65..ce15569196 100644
--- a/libavcodec/dynamic_hdr10_plus.c
+++ b/libavcodec/dynamic_hdr10_plus.c
@@ -18,6 +18,12 @@ 
 
 #include "dynamic_hdr10_plus.h"
 #include "get_bits.h"
+#include "put_bits.h"
+
+static const uint8_t usa_country_code = 0xB5;
+static const uint16_t smpte_provider_code = 0x003C;
+static const uint16_t smpte2094_40_provider_oriented_code = 0x0001;
+static const uint16_t smpte2094_40_application_identifier = 0x04;
 
 static const int64_t luminance_den = 1;
 static const int32_t peak_luminance_den = 15;
@@ -27,8 +33,8 @@  static const int32_t knee_point_den = 4095;
 static const int32_t bezier_anchor_den = 1023;
 static const int32_t saturation_weight_den = 8;
 
-int ff_parse_itu_t_t35_to_dynamic_hdr10_plus(AVDynamicHDRPlus *s, const uint8_t *data,
-                                             int size)
+int ff_parse_itu_t_t35_to_dynamic_hdr10_plus(AVDynamicHDRPlus* s, const uint8_t* data,
+					     int size)
 {
     GetBitContext gbc, *gb = &gbc;
     int ret;
@@ -40,10 +46,12 @@  int ff_parse_itu_t_t35_to_dynamic_hdr10_plus(AVDynamicHDRPlus *s, const uint8_t
     if (ret < 0)
         return ret;
 
-    if (get_bits_left(gb) < 10)
+    if (get_bits_left(gb) < 8)
         return AVERROR_INVALIDDATA;
+     s->application_version = get_bits(gb, 8);
 
-    s->application_version = get_bits(gb, 8);
+    if (get_bits_left(gb) < 2)
+        return AVERROR_INVALIDDATA;
     s->num_windows = get_bits(gb, 2);
 
     if (s->num_windows < 1 || s->num_windows > 3) {
@@ -56,15 +64,11 @@  int ff_parse_itu_t_t35_to_dynamic_hdr10_plus(AVDynamicHDRPlus *s, const uint8_t
     for (int w = 1; w < s->num_windows; w++) {
         // The corners are set to absolute coordinates here. They should be
         // converted to the relative coordinates (in [0, 1]) in the decoder.
-        AVHDRPlusColorTransformParams *params = &s->params[w];
-        params->window_upper_left_corner_x =
-            (AVRational){get_bits(gb, 16), 1};
-        params->window_upper_left_corner_y =
-            (AVRational){get_bits(gb, 16), 1};
-        params->window_lower_right_corner_x =
-            (AVRational){get_bits(gb, 16), 1};
-        params->window_lower_right_corner_y =
-            (AVRational){get_bits(gb, 16), 1};
+        AVHDRPlusColorTransformParams* params = &s->params[w];
+        params->window_upper_left_corner_x = (AVRational) { get_bits(gb, 16), 1 };
+        params->window_upper_left_corner_y = (AVRational) { get_bits(gb, 16), 1 };
+        params->window_lower_right_corner_x = (AVRational) { get_bits(gb, 16), 1 };
+        params->window_lower_right_corner_y = (AVRational) { get_bits(gb, 16), 1 };
 
         params->center_of_ellipse_x = get_bits(gb, 16);
         params->center_of_ellipse_y = get_bits(gb, 16);
@@ -78,8 +82,7 @@  int ff_parse_itu_t_t35_to_dynamic_hdr10_plus(AVDynamicHDRPlus *s, const uint8_t
     if (get_bits_left(gb) < 28)
         return AVERROR_INVALIDDATA;
 
-    s->targeted_system_display_maximum_luminance =
-        (AVRational){get_bits_long(gb, 27), luminance_den};
+    s->targeted_system_display_maximum_luminance = (AVRational) { get_bits_long(gb, 27), luminance_den };
     s->targeted_system_display_actual_peak_luminance_flag = get_bits1(gb);
 
     if (s->targeted_system_display_actual_peak_luminance_flag) {
@@ -99,22 +102,19 @@  int ff_parse_itu_t_t35_to_dynamic_hdr10_plus(AVDynamicHDRPlus *s, const uint8_t
 
         for (int i = 0; i < rows; i++) {
             for (int j = 0; j < cols; j++) {
-                s->targeted_system_display_actual_peak_luminance[i][j] =
-                    (AVRational){get_bits(gb, 4), peak_luminance_den};
+                s->targeted_system_display_actual_peak_luminance[i][j] = (AVRational) { get_bits(gb, 4), peak_luminance_den };
             }
         }
     }
     for (int w = 0; w < s->num_windows; w++) {
-        AVHDRPlusColorTransformParams *params = &s->params[w];
+        AVHDRPlusColorTransformParams* params = &s->params[w];
         if (get_bits_left(gb) < (3 * 17 + 17 + 4))
             return AVERROR_INVALIDDATA;
 
         for (int i = 0; i < 3; i++) {
-            params->maxscl[i] =
-                (AVRational){get_bits(gb, 17), rgb_den};
+            params->maxscl[i] = (AVRational) { get_bits(gb, 17), rgb_den };
         }
-        params->average_maxrgb =
-            (AVRational){get_bits(gb, 17), rgb_den};
+        params->average_maxrgb = (AVRational) { get_bits(gb, 17), rgb_den };
         params->num_distribution_maxrgb_percentiles = get_bits(gb, 4);
 
         if (get_bits_left(gb) <
@@ -123,14 +123,13 @@  int ff_parse_itu_t_t35_to_dynamic_hdr10_plus(AVDynamicHDRPlus *s, const uint8_t
 
         for (int i = 0; i < params->num_distribution_maxrgb_percentiles; i++) {
             params->distribution_maxrgb[i].percentage = get_bits(gb, 7);
-            params->distribution_maxrgb[i].percentile =
-                (AVRational){get_bits(gb, 17), rgb_den};
+            params->distribution_maxrgb[i].percentile = (AVRational) { get_bits(gb, 17), rgb_den };
         }
 
         if (get_bits_left(gb) < 10)
             return AVERROR_INVALIDDATA;
 
-        params->fraction_bright_pixels = (AVRational){get_bits(gb, 10), fraction_pixel_den};
+        params->fraction_bright_pixels = (AVRational) { get_bits(gb, 10), fraction_pixel_den };
     }
     if (get_bits_left(gb) < 1)
         return AVERROR_INVALIDDATA;
@@ -152,14 +151,13 @@  int ff_parse_itu_t_t35_to_dynamic_hdr10_plus(AVDynamicHDRPlus *s, const uint8_t
 
         for (int i = 0; i < rows; i++) {
             for (int j = 0; j < cols; j++) {
-                s->mastering_display_actual_peak_luminance[i][j] =
-                    (AVRational){get_bits(gb, 4), peak_luminance_den};
+                s->mastering_display_actual_peak_luminance[i][j] = (AVRational) { get_bits(gb, 4), peak_luminance_den };
             }
         }
     }
 
     for (int w = 0; w < s->num_windows; w++) {
-        AVHDRPlusColorTransformParams *params = &s->params[w];
+        AVHDRPlusColorTransformParams* params = &s->params[w];
         if (get_bits_left(gb) < 1)
             return AVERROR_INVALIDDATA;
 
@@ -168,18 +166,15 @@  int ff_parse_itu_t_t35_to_dynamic_hdr10_plus(AVDynamicHDRPlus *s, const uint8_t
             if (get_bits_left(gb) < 28)
                 return AVERROR_INVALIDDATA;
 
-            params->knee_point_x =
-                (AVRational){get_bits(gb, 12), knee_point_den};
-            params->knee_point_y =
-                (AVRational){get_bits(gb, 12), knee_point_den};
+            params->knee_point_x = (AVRational) { get_bits(gb, 12), knee_point_den };
+            params->knee_point_y = (AVRational) { get_bits(gb, 12), knee_point_den };
             params->num_bezier_curve_anchors = get_bits(gb, 4);
 
             if (get_bits_left(gb) < (params->num_bezier_curve_anchors * 10))
                 return AVERROR_INVALIDDATA;
 
             for (int i = 0; i < params->num_bezier_curve_anchors; i++) {
-                params->bezier_curve_anchors[i] =
-                    (AVRational){get_bits(gb, 10), bezier_anchor_den};
+                params->bezier_curve_anchors[i] = (AVRational) { get_bits(gb, 10), bezier_anchor_den };
             }
         }
 
@@ -196,3 +191,209 @@  int ff_parse_itu_t_t35_to_dynamic_hdr10_plus(AVDynamicHDRPlus *s, const uint8_t
 
     return 0;
 }
+
+int ff_parse_full_itu_t_t35_to_dynamic_hdr10_plus(AVDynamicHDRPlus* s, const uint8_t* data,
+					     int size)
+{
+    uint8_t country_code;
+    uint16_t provider_code;
+    uint16_t provider_oriented_code;
+    uint8_t application_identifier;
+    GetBitContext gbc, *gb = &gbc;
+    int ret, offset;
+
+    if (!s)
+        return AVERROR(ENOMEM);
+
+    if (size < 7)
+        return AVERROR_INVALIDDATA;
+
+    ret = init_get_bits8(gb, data, size);
+    if (ret < 0)
+        return ret;
+
+    country_code = get_bits(gb, 8);
+    provider_code = get_bits(gb, 16);
+
+    if (country_code != usa_country_code ||
+        provider_code != smpte_provider_code)
+        return AVERROR_INVALIDDATA;
+
+    // A/341 Amendment – 2094-40
+    provider_oriented_code = get_bits(gb, 16);
+    application_identifier = get_bits(gb, 8);
+    if (provider_oriented_code != smpte2094_40_provider_oriented_code ||
+        application_identifier != smpte2094_40_application_identifier)
+        return AVERROR_INVALIDDATA;
+
+    offset = get_bits_count(gb) / 8;
+
+    return ff_parse_itu_t_t35_to_dynamic_hdr10_plus(s, gb->buffer + offset, size - offset);
+}
+
+int ff_itu_t_t35_buffer_size(const AVDynamicHDRPlus* s)
+{
+    int bit_count = 0;
+    int w, size;
+
+    if (!s)
+        return 0;
+
+    // 7 bytes for country code, provider code, and user identifier.
+    bit_count += 56;
+
+    if (s->num_windows < 1 || s->num_windows > 3)
+        return 0;
+    // Count bits for window params.
+    bit_count += 2 + ((19 * 8 + 1) * (s->num_windows - 1));
+
+    bit_count += 28;
+    if (s->targeted_system_display_actual_peak_luminance_flag) {
+        int rows, cols;
+        rows = s->num_rows_targeted_system_display_actual_peak_luminance;
+        cols = s->num_cols_targeted_system_display_actual_peak_luminance;
+        if (((rows < 2) || (rows > 25)) || ((cols < 2) || (cols > 25)))
+            return 0;
+
+        bit_count += (10 + rows * cols * 4);
+    }
+    for (w = 0; w < s->num_windows; w++) {
+        bit_count += (3 * 17 + 17 + 4 + 10) + (s->params[w].num_distribution_maxrgb_percentiles * 24);
+    }
+    bit_count++;
+
+    if (s->mastering_display_actual_peak_luminance_flag) {
+        int rows, cols;
+        rows = s->num_rows_mastering_display_actual_peak_luminance;
+        cols = s->num_cols_mastering_display_actual_peak_luminance;
+        if (((rows < 2) || (rows > 25)) || ((cols < 2) || (cols > 25)))
+            return 0;
+
+        bit_count += (10 + rows * cols * 4);
+    }
+
+    for (w = 0; w < s->num_windows; w++) {
+        bit_count++;
+        if (s->params[w].tone_mapping_flag)
+            bit_count += (28 + s->params[w].num_bezier_curve_anchors * 10);
+
+        bit_count++;
+        if (s->params[w].color_saturation_mapping_flag)
+            bit_count += 6;
+    }
+    size = bit_count / 8;
+    if (bit_count % 8 != 0)
+        size++;
+    return size;
+}
+
+int ff_write_dynamic_hdr10_plus_to_full_itu_t_t35(const AVDynamicHDRPlus* s, uint8_t** data, size_t* size)
+{
+    int w, i, j;
+    PutBitContext pbc, *pb = &pbc;
+
+    if (!s || !size)
+        return AVERROR(EINVAL);
+
+    *size = ff_itu_t_t35_buffer_size(s);
+    if (*size <= 0)
+        return AVERROR(EINVAL);
+    *data = av_mallocz(*size);
+    init_put_bits(pb, *data, *size);
+    if (put_bits_left(pb) < *size) {
+        av_freep(data);
+        return AVERROR(EINVAL);
+    }
+    put_bits(pb, 8, usa_country_code);
+
+    put_bits(pb, 16, smpte_provider_code);
+    put_bits(pb, 16, smpte2094_40_provider_oriented_code);
+    put_bits(pb, 8, smpte2094_40_application_identifier);
+    put_bits(pb, 8, s->application_version);
+
+    put_bits(pb, 2, s->num_windows);
+
+    for (w = 1; w < s->num_windows; w++) {
+        put_bits(pb, 16, s->params[w].window_upper_left_corner_x.num / s->params[w].window_upper_left_corner_x.den);
+        put_bits(pb, 16, s->params[w].window_upper_left_corner_y.num / s->params[w].window_upper_left_corner_y.den);
+        put_bits(pb, 16, s->params[w].window_lower_right_corner_x.num / s->params[w].window_lower_right_corner_x.den);
+        put_bits(pb, 16, s->params[w].window_lower_right_corner_y.num / s->params[w].window_lower_right_corner_y.den);
+        put_bits(pb, 16, s->params[w].center_of_ellipse_x);
+        put_bits(pb, 16, s->params[w].center_of_ellipse_y);
+        put_bits(pb, 8, s->params[w].rotation_angle);
+        put_bits(pb, 16, s->params[w].semimajor_axis_internal_ellipse);
+        put_bits(pb, 16, s->params[w].semimajor_axis_external_ellipse);
+        put_bits(pb, 16, s->params[w].semiminor_axis_external_ellipse);
+        put_bits(pb, 1, s->params[w].overlap_process_option);
+    }
+    put_bits(pb, 27,
+             s->targeted_system_display_maximum_luminance.num * luminance_den / s->targeted_system_display_maximum_luminance.den);
+    put_bits(pb, 1, s->targeted_system_display_actual_peak_luminance_flag);
+    if (s->targeted_system_display_actual_peak_luminance_flag) {
+        int rows, cols;
+        rows = s->num_rows_targeted_system_display_actual_peak_luminance;
+        cols = s->num_cols_targeted_system_display_actual_peak_luminance;
+        put_bits(pb, 5, rows);
+        put_bits(pb, 5, cols);
+        for (i = 0; i < rows; i++) {
+            for (j = 0; j < cols; j++) {
+                put_bits(
+                    pb, 4,
+                    s->targeted_system_display_actual_peak_luminance[i][j].num * peak_luminance_den / s->targeted_system_display_actual_peak_luminance[i][j].den);
+            }
+        }
+    }
+    for (w = 0; w < s->num_windows; w++) {
+        for (i = 0; i < 3; i++) {
+            put_bits(pb, 17,
+                     s->params[w].maxscl[i].num * rgb_den / s->params[w].maxscl[i].den);
+        }
+        put_bits(pb, 17,
+                 s->params[w].average_maxrgb.num * rgb_den / s->params[w].average_maxrgb.den);
+        put_bits(pb, 4, s->params[w].num_distribution_maxrgb_percentiles);
+
+        for (i = 0; i < s->params[w].num_distribution_maxrgb_percentiles; i++) {
+            put_bits(pb, 7, s->params[w].distribution_maxrgb[i].percentage);
+            put_bits(pb, 17,
+                     s->params[w].distribution_maxrgb[i].percentile.num * rgb_den / s->params[w].distribution_maxrgb[i].percentile.den);
+        }
+        put_bits(pb, 10,
+                 s->params[w].fraction_bright_pixels.num * fraction_pixel_den / s->params[w].fraction_bright_pixels.den);
+    }
+    put_bits(pb, 1, s->mastering_display_actual_peak_luminance_flag);
+    if (s->mastering_display_actual_peak_luminance_flag) {
+        int rows, cols;
+        rows = s->num_rows_mastering_display_actual_peak_luminance;
+        cols = s->num_cols_mastering_display_actual_peak_luminance;
+        put_bits(pb, 5, rows);
+        put_bits(pb, 5, cols);
+        for (i = 0; i < rows; i++) {
+            for (j = 0; j < cols; j++) {
+                put_bits(
+                    pb, 4,
+                    s->mastering_display_actual_peak_luminance[i][j].num * peak_luminance_den / s->mastering_display_actual_peak_luminance[i][j].den);
+            }
+        }
+    }
+
+    for (w = 0; w < s->num_windows; w++) {
+        put_bits(pb, 1, s->params[w].tone_mapping_flag);
+        if (s->params[w].tone_mapping_flag) {
+            put_bits(pb, 12,
+                     s->params[w].knee_point_x.num * knee_point_den / s->params[w].knee_point_x.den);
+            put_bits(pb, 12,
+                     s->params[w].knee_point_y.num * knee_point_den / s->params[w].knee_point_y.den);
+            put_bits(pb, 4, s->params[w].num_bezier_curve_anchors);
+            for (i = 0; i < s->params[w].num_bezier_curve_anchors; i++) {
+                put_bits(pb, 10,
+                         s->params[w].bezier_curve_anchors[i].num * bezier_anchor_den / s->params[w].bezier_curve_anchors[i].den);
+            }
+        }
+        put_bits(pb, 1, s->params[w].color_saturation_mapping_flag);
+        if (s->params[w].color_saturation_mapping_flag)
+            put_bits(pb, 6,
+                     s->params[w].color_saturation_weight.num * saturation_weight_den / s->params[w].color_saturation_weight.den);
+    }
+    flush_put_bits(pb);
+    return 0;
+}
diff --git a/libavcodec/dynamic_hdr10_plus.h b/libavcodec/dynamic_hdr10_plus.h
index cd7acf0432..dafe548d2d 100644
--- a/libavcodec/dynamic_hdr10_plus.h
+++ b/libavcodec/dynamic_hdr10_plus.h
@@ -29,7 +29,38 @@ 
  *
  * @return 0 if succeed. Otherwise, returns the appropriate AVERROR.
  */
-int ff_parse_itu_t_t35_to_dynamic_hdr10_plus(AVDynamicHDRPlus *s, const uint8_t *data,
-                                             int size);
+int ff_parse_itu_t_t35_to_dynamic_hdr10_plus(AVDynamicHDRPlus* s, const uint8_t* data,
+					     int size);
+
+/**
+ * Parse the user data registered ITU-T T.35 with header to AVDynamicHDRPlus. At first check
+ * the header if the provider code is SMPTE-2094-40. Then will parse the data to AVDynamicHDRPlus.
+ * @param s A pointer containing the decoded AVDynamicHDRPlus structure.
+ * @param data The byte array containing the raw ITU-T T.35 data with header.
+ * @param size Size of the data array in bytes.
+ *
+ * @return 0 if succeed. Otherwise, returns the appropriate AVERROR.
+ */
+int ff_parse_full_itu_t_t35_to_dynamic_hdr10_plus(AVDynamicHDRPlus* s, const uint8_t* data,
+					     int size);
+
+/**
+ * Get the size of buffer required to save the encoded bit stream of
+ * AVDynamicHDRPlus in the form of the user data registered ITU-T T.35.
+ * @param s The AVDynamicHDRPlus structure.
+ *
+ * @return The size of bit stream required for encoding. 0 if the data is invalid.
+ */
+int ff_itu_t_t35_buffer_size(const AVDynamicHDRPlus* s);
+
+/**
+ * Encode and write AVDynamicHDRPlus to the user data registered ITU-T T.3 with header (containing the provider code).
+ * @param s A pointer containing the AVDynamicHDRPlus structure.
+ * @param data The byte array containing the raw ITU-T T.35 data with header.
+ * @param size The size of the raw ITU-T T.35 data.
+ *
+ * @return 0 if succeed. Otherwise, returns the appropriate AVERROR.
+ */
+int ff_write_dynamic_hdr10_plus_to_full_itu_t_t35(const AVDynamicHDRPlus* s, uint8_t** data, size_t* size);
 
 #endif /* AVCODEC_DYNAMIC_HDR10_PLUS_H */
diff --git a/libavformat/matroska.h b/libavformat/matroska.h
index 45077ed33f..c3cf9eef53 100644
--- a/libavformat/matroska.h
+++ b/libavformat/matroska.h
@@ -358,6 +358,11 @@  typedef enum {
   MATROSKA_VIDEO_PROJECTION_TYPE_MESH               = 3,
 } MatroskaVideoProjectionType;
 
+typedef enum {
+  MATROSKA_BLOCK_ADD_ID_DEFAULT                     = 0,
+  MATROSKA_BLOCK_ADD_ID_DYNAMIC_HDR10_PLUS          = 4,
+} MatroskaBlockAddID;
+
 /*
  * Matroska Codec IDs, strings
  */
diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index d97fc33d44..de8adf12ee 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -49,6 +49,7 @@ 
 #include "libavutil/spherical.h"
 
 #include "libavcodec/bytestream.h"
+#include "libavcodec/dynamic_hdr10_plus.h"
 #include "libavcodec/flac.h"
 #include "libavcodec/mpeg4audio.h"
 #include "libavcodec/packet_internal.h"
@@ -3632,15 +3633,28 @@  static int matroska_parse_frame(MatroskaDemuxContext *matroska,
     pkt->stream_index = st->index;
 
     if (additional_size > 0) {
-        uint8_t *side_data = av_packet_new_side_data(pkt,
-                                                     AV_PKT_DATA_MATROSKA_BLOCKADDITIONAL,
-                                                     additional_size + 8);
-        if (!side_data) {
-            av_packet_unref(pkt);
-            return AVERROR(ENOMEM);
+        if (additional_id == MATROSKA_BLOCK_ADD_ID_DYNAMIC_HDR10_PLUS) {
+            AVDynamicHDRPlus hdr10_plus;
+            if (!ff_parse_full_itu_t_t35_to_dynamic_hdr10_plus(&hdr10_plus, additional, additional_size)) {
+                uint8_t *side_data = av_packet_new_side_data(pkt, AV_PKT_DATA_DYNAMIC_HDR10_PLUS, sizeof(hdr10_plus));
+                if (!side_data) {
+                    av_packet_unref(pkt);
+                    av_free(pkt);
+                    return AVERROR(ENOMEM);
+                }
+                memcpy(side_data, (uint8_t*)(&hdr10_plus), sizeof(hdr10_plus));
+                }
+	} else {
+	    uint8_t *side_data = av_packet_new_side_data(pkt,
+                                                         AV_PKT_DATA_MATROSKA_BLOCKADDITIONAL,
+                                                         additional_size + 8);
+            if (!side_data) {
+                av_packet_unref(pkt);
+                return AVERROR(ENOMEM);
+            }
+            AV_WB64(side_data, additional_id);
+            memcpy(side_data + 8, additional, additional_size);
         }
-        AV_WB64(side_data, additional_id);
-        memcpy(side_data + 8, additional, additional_size);
     }
 
     if (discard_padding) {
diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 3b8ca11f28..7a775e7d4e 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -56,6 +56,7 @@ 
 #include "libavutil/samplefmt.h"
 #include "libavutil/stereo3d.h"
 
+#include "libavcodec/dynamic_hdr10_plus.h"
 #include "libavcodec/xiph.h"
 #include "libavcodec/mpeg4audio.h"
 
@@ -2412,7 +2413,7 @@  static int mkv_write_header(AVFormatContext *s)
 
 #if CONFIG_MATROSKA_MUXER
 static int mkv_reformat_h2645(MatroskaMuxContext *mkv, AVIOContext *pb,
-                              const AVPacket *pkt, int *size)
+                               const AVPacket *pkt, int *size)
 {
     int ret;
     if (pb) {
@@ -2513,9 +2514,12 @@  static int mkv_write_block(void *logctx, MatroskaMuxContext *mkv,
 {
     uint8_t *side_data;
     size_t side_data_size;
-    uint64_t additional_id;
+    uint64_t additional_id = 0;
     int64_t discard_padding = 0;
     unsigned track_number = track->track_num;
+    int has_codec_specific_blockmore = 0;
+    uint8_t *hdr10_plus_itu_t_t35;
+    size_t hdr10_plus_itu_t_t35_size = 0;
     EBML_WRITER(9);
 
     mkv->cur_block.track  = track;
@@ -2547,24 +2551,38 @@  static int mkv_write_block(void *logctx, MatroskaMuxContext *mkv,
                                        (AVRational){1, 1000000000});
         ebml_writer_add_sint(&writer, MATROSKA_ID_DISCARDPADDING, discard_padding);
     }
+    side_data = av_packet_get_side_data(pkt,
+                                        AV_PKT_DATA_DYNAMIC_HDR10_PLUS,
+                                        &side_data_size);
+    if (side_data && side_data_size > 0)
+        ff_write_dynamic_hdr10_plus_to_full_itu_t_t35((AVDynamicHDRPlus*)side_data, &hdr10_plus_itu_t_t35, &hdr10_plus_itu_t_t35_size);
 
     side_data = av_packet_get_side_data(pkt,
                                         AV_PKT_DATA_MATROSKA_BLOCKADDITIONAL,
                                         &side_data_size);
-    if (side_data && side_data_size >= 8 &&
-        // Only the Codec-specific BlockMore (id == 1) is currently supported.
-        (additional_id = AV_RB64(side_data)) == 1) {
+    has_codec_specific_blockmore = side_data && side_data_size >= 8 &&
+                                   (additional_id = AV_RB64(side_data)) == 1;
+    // The Codec-specific BlockMore (id == 1) and HDR10+ (id == 4) are supported.
+    if (has_codec_specific_blockmore || hdr10_plus_itu_t_t35_size > 0) {
         ebml_writer_open_master(&writer, MATROSKA_ID_BLOCKADDITIONS);
-        ebml_writer_open_master(&writer, MATROSKA_ID_BLOCKMORE);
-        /* Until dbc50f8a our demuxer used a wrong default value
-         * of BlockAddID, so we write it unconditionally. */
-        ebml_writer_add_uint(&writer, MATROSKA_ID_BLOCKADDID, additional_id);
-        ebml_writer_add_bin (&writer, MATROSKA_ID_BLOCKADDITIONAL,
-                             side_data + 8, side_data_size - 8);
-        ebml_writer_close_master(&writer);
+	if (has_codec_specific_blockmore) {
+            ebml_writer_open_master(&writer, MATROSKA_ID_BLOCKMORE);
+            /* Until dbc50f8a our demuxer used a wrong default value
+             * of BlockAddID, so we write it unconditionally. */
+            ebml_writer_add_uint(&writer, MATROSKA_ID_BLOCKADDID, additional_id);
+            ebml_writer_add_bin (&writer, MATROSKA_ID_BLOCKADDITIONAL,
+                                 side_data + 8, side_data_size - 8);
+            ebml_writer_close_master(&writer);
+	}
+	if (hdr10_plus_itu_t_t35_size > 0) {
+            ebml_writer_open_master(&writer, MATROSKA_ID_BLOCKMORE);
+            ebml_writer_add_uint(&writer, MATROSKA_ID_BLOCKADDID, MATROSKA_BLOCK_ADD_ID_DYNAMIC_HDR10_PLUS);
+            ebml_writer_add_bin (&writer, MATROSKA_ID_BLOCKADDITIONAL,
+                                 hdr10_plus_itu_t_t35, hdr10_plus_itu_t_t35_size);
+            ebml_writer_close_master(&writer);
+	}
         ebml_writer_close_master(&writer);
     }
-
     if (!force_blockgroup && writer.nb_elements == 2) {
         /* Nothing except the BlockGroup + Block. Can use a SimpleBlock. */
         writer.elements++;    // Skip the BlockGroup.
diff --git a/tests/fate/matroska.mak b/tests/fate/matroska.mak
index 3073b0a061..43800cb2d7 100644
--- a/tests/fate/matroska.mak
+++ b/tests/fate/matroska.mak
@@ -135,6 +135,12 @@  FATE_MATROSKA_FFMPEG_FFPROBE-$(call ALLYES, MATROSKA_DEMUXER MATROSKA_MUXER \
                                += fate-matroska-spherical-mono-remux
 fate-matroska-spherical-mono-remux: CMD = transcode matroska $(TARGET_SAMPLES)/mkv/spherical.mkv matroska "-map 0 -map 0 -c copy -disposition:0 -default+forced -disposition:1 -default -default_mode passthrough -color_primaries:1 bt709 -color_trc:1 smpte170m -colorspace:1 bt2020c -color_range:1 pc"  "-map 0 -c copy -t 0" "" "-show_entries stream_side_data_list:stream_disposition=default,forced:stream=color_range,color_space,color_primaries,color_transfer"
 
+# The input file of the following test contains HDR10+ metadata and so this
+# test tests correct encoding and decoding HDR10+ for VP9/MKV.
+FATE_MATROSKA_FFMPEG_FFPROBE-$(call ALLYES, MATROSKA_DEMUXER MATROSKA_MUXER) \
+                               += fate-matroska-hdr10-plus-metadata
+fate-matroska-hdr10-plus-metadata: CMD = transcode matroska $(TARGET_SAMPLES)/mkv/hdr10_plus_vp9_sample.mkv matroska "-map 0 -map 0 -c copy -pixel_format yuv420p10le" "" "" "-show_frames"
+
 # The input file of the following test contains Content Light Level as well as
 # Mastering Display Metadata and so this test tests correct muxing and demuxing
 # of these. It furthermore also tests that this data is correctly propagated
diff --git a/tests/ref/fate/matroska-hdr10-plus-metadata b/tests/ref/fate/matroska-hdr10-plus-metadata
new file mode 100644
index 0000000000..a461fb9674
--- /dev/null
+++ b/tests/ref/fate/matroska-hdr10-plus-metadata
@@ -0,0 +1,152 @@ 
+8e184fbb8ec8bf26c54ceb15c21108f4 *tests/data/fate/matroska-hdr10-plus-metadata.matroska
+27476 tests/data/fate/matroska-hdr10-plus-metadata.matroska
+#tb 0: 1/25
+#media_type 0: video
+#codec_id 0: rawvideo
+#dimensions 0: 1280x720
+#sar 0: 1/1
+0,          0,          0,        1,  2764800, 0xf2617bf2
+[FRAME]
+media_type=video
+stream_index=0
+key_frame=1
+pts=0
+pts_time=0.000000
+pkt_dts=0
+pkt_dts_time=0.000000
+best_effort_timestamp=0
+best_effort_timestamp_time=0.000000
+pkt_duration=40
+pkt_duration_time=0.040000
+pkt_pos=559
+pkt_size=13350
+width=1280
+height=720
+pix_fmt=yuv420p10le
+sample_aspect_ratio=1:1
+pict_type=I
+coded_picture_number=0
+display_picture_number=0
+interlaced_frame=0
+top_field_first=0
+repeat_pict=0
+color_range=tv
+color_space=unknown
+color_primaries=unknown
+color_transfer=unknown
+chroma_location=unspecified
+[SIDE_DATA]
+side_data_type=HDR Dynamic Metadata SMPTE2094-40 (HDR10+)
+application version=1
+num_windows=1
+targeted_system_display_maximum_luminance=400/1
+maxscl=3340/100000
+maxscl=2870/100000
+maxscl=2720/100000
+average_maxrgb=510/100000
+num_distribution_maxrgb_percentiles=9
+distribution_maxrgb_percentage=1
+distribution_maxrgb_percentile=30/100000
+distribution_maxrgb_percentage=5
+distribution_maxrgb_percentile=2940/100000
+distribution_maxrgb_percentage=10
+distribution_maxrgb_percentile=255/100000
+distribution_maxrgb_percentage=25
+distribution_maxrgb_percentile=70/100000
+distribution_maxrgb_percentage=50
+distribution_maxrgb_percentile=1340/100000
+distribution_maxrgb_percentage=75
+distribution_maxrgb_percentile=1600/100000
+distribution_maxrgb_percentage=90
+distribution_maxrgb_percentile=1850/100000
+distribution_maxrgb_percentage=95
+distribution_maxrgb_percentile=1950/100000
+distribution_maxrgb_percentage=99
+distribution_maxrgb_percentile=2940/100000
+fraction_bright_pixels=1/1000
+knee_point_x=0/4095
+knee_point_y=0/4095
+num_bezier_curve_anchors=9
+bezier_curve_anchors=102/1023
+bezier_curve_anchors=205/1023
+bezier_curve_anchors=307/1023
+bezier_curve_anchors=410/1023
+bezier_curve_anchors=512/1023
+bezier_curve_anchors=614/1023
+bezier_curve_anchors=717/1023
+bezier_curve_anchors=819/1023
+bezier_curve_anchors=922/1023
+[/SIDE_DATA]
+[/FRAME]
+[FRAME]
+media_type=video
+stream_index=1
+key_frame=1
+pts=0
+pts_time=0.000000
+pkt_dts=0
+pkt_dts_time=0.000000
+best_effort_timestamp=0
+best_effort_timestamp_time=0.000000
+pkt_duration=40
+pkt_duration_time=0.040000
+pkt_pos=14008
+pkt_size=13350
+width=1280
+height=720
+pix_fmt=yuv420p10le
+sample_aspect_ratio=1:1
+pict_type=I
+coded_picture_number=0
+display_picture_number=0
+interlaced_frame=0
+top_field_first=0
+repeat_pict=0
+color_range=tv
+color_space=unknown
+color_primaries=unknown
+color_transfer=unknown
+chroma_location=unspecified
+[SIDE_DATA]
+side_data_type=HDR Dynamic Metadata SMPTE2094-40 (HDR10+)
+application version=1
+num_windows=1
+targeted_system_display_maximum_luminance=400/1
+maxscl=3340/100000
+maxscl=2870/100000
+maxscl=2720/100000
+average_maxrgb=510/100000
+num_distribution_maxrgb_percentiles=9
+distribution_maxrgb_percentage=1
+distribution_maxrgb_percentile=30/100000
+distribution_maxrgb_percentage=5
+distribution_maxrgb_percentile=2940/100000
+distribution_maxrgb_percentage=10
+distribution_maxrgb_percentile=255/100000
+distribution_maxrgb_percentage=25
+distribution_maxrgb_percentile=70/100000
+distribution_maxrgb_percentage=50
+distribution_maxrgb_percentile=1340/100000
+distribution_maxrgb_percentage=75
+distribution_maxrgb_percentile=1600/100000
+distribution_maxrgb_percentage=90
+distribution_maxrgb_percentile=1850/100000
+distribution_maxrgb_percentage=95
+distribution_maxrgb_percentile=1950/100000
+distribution_maxrgb_percentage=99
+distribution_maxrgb_percentile=2940/100000
+fraction_bright_pixels=1/1000
+knee_point_x=0/4095
+knee_point_y=0/4095
+num_bezier_curve_anchors=9
+bezier_curve_anchors=102/1023
+bezier_curve_anchors=205/1023
+bezier_curve_anchors=307/1023
+bezier_curve_anchors=410/1023
+bezier_curve_anchors=512/1023
+bezier_curve_anchors=614/1023
+bezier_curve_anchors=717/1023
+bezier_curve_anchors=819/1023
+bezier_curve_anchors=922/1023
+[/SIDE_DATA]
+[/FRAME]