diff --git a/doc/APIchanges b/doc/APIchanges
index cd1902179f..6eefc7fc33 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -14,6 +14,9 @@ libavutil:     2021-04-27
 
 API changes, most recent first:
 
+2021-08-02 - xxxxxxxxxx - lavc 59.4.100 - packet.h
+  Add AVPacket.opaque, AVPacket.opaque_ref, AVPacket.time_base.
+
 2021-07-23 - xxxxxxxxxx - lavu 57.3.100 - common.h macros.h
   Move several macros (AV_NE, FFDIFFSIGN, FFMAX, FFMAX3, FFMIN, FFMIN3,
   FFSWAP, FF_ARRAY_ELEMS, MKTAG, MKBETAG) from common.h to macros.h.
diff --git a/libavcodec/avpacket.c b/libavcodec/avpacket.c
index 800bee3489..075b219475 100644
--- a/libavcodec/avpacket.c
+++ b/libavcodec/avpacket.c
@@ -26,6 +26,7 @@
 #include "libavutil/internal.h"
 #include "libavutil/mathematics.h"
 #include "libavutil/mem.h"
+#include "libavutil/rational.h"
 
 #include "bytestream.h"
 #include "internal.h"
@@ -44,6 +45,9 @@ void av_init_packet(AVPacket *pkt)
     pkt->buf                  = NULL;
     pkt->side_data            = NULL;
     pkt->side_data_elems      = 0;
+    pkt->opaque               = NULL;
+    pkt->opaque_ref           = NULL;
+    pkt->time_base            = av_make_q(0, 0);
 }
 #endif
 
@@ -374,7 +378,7 @@ int av_packet_shrink_side_data(AVPacket *pkt, enum AVPacketSideDataType type,
 
 int av_packet_copy_props(AVPacket *dst, const AVPacket *src)
 {
-    int i;
+    int i, ret;
 
     dst->pts                  = src->pts;
     dst->dts                  = src->dts;
@@ -382,9 +386,16 @@ int av_packet_copy_props(AVPacket *dst, const AVPacket *src)
     dst->duration             = src->duration;
     dst->flags                = src->flags;
     dst->stream_index         = src->stream_index;
-
+    dst->opaque               = src->opaque;
+    dst->time_base            = src->time_base;
+    dst->opaque_ref           = NULL;
     dst->side_data            = NULL;
     dst->side_data_elems      = 0;
+
+    ret = av_buffer_replace(&dst->opaque_ref, src->opaque_ref);
+    if (ret < 0)
+        return ret;
+
     for (i = 0; i < src->side_data_elems; i++) {
         enum AVPacketSideDataType type = src->side_data[i].type;
         size_t size = src->side_data[i].size;
@@ -392,6 +403,7 @@ int av_packet_copy_props(AVPacket *dst, const AVPacket *src)
         uint8_t *dst_data = av_packet_new_side_data(dst, type, size);
 
         if (!dst_data) {
+            av_buffer_unref(&dst->opaque_ref);
             av_packet_free_side_data(dst);
             return AVERROR(ENOMEM);
         }
@@ -404,6 +416,7 @@ int av_packet_copy_props(AVPacket *dst, const AVPacket *src)
 void av_packet_unref(AVPacket *pkt)
 {
     av_packet_free_side_data(pkt);
+    av_buffer_unref(&pkt->opaque_ref);
     av_buffer_unref(&pkt->buf);
     get_packet_defaults(pkt);
 }
diff --git a/libavcodec/packet.h b/libavcodec/packet.h
index a9d3a9b596..9baff24635 100644
--- a/libavcodec/packet.h
+++ b/libavcodec/packet.h
@@ -391,6 +391,27 @@ typedef struct AVPacket {
     int64_t duration;
 
     int64_t pos;                            ///< byte position in stream, -1 if unknown
+
+    /**
+     * for some private data of the user
+     */
+    void *opaque;
+
+    /**
+     * AVBufferRef for free use by the API user. FFmpeg will never check the
+     * contents of the buffer ref. FFmpeg calls av_buffer_unref() on it when
+     * the packet is unreferenced. av_packet_copy_props() calls create a new
+     * reference with av_buffer_ref() for the target packet's opaque_ref field.
+     *
+     * This is unrelated to the opaque field, although it serves a similar
+     * purpose.
+     */
+    AVBufferRef *opaque_ref;
+
+    /**
+     * Time base of the packet's timestamps.
+     */
+    AVRational time_base;
 } AVPacket;
 
 #if FF_API_INIT_PACKET
diff --git a/libavcodec/version.h b/libavcodec/version.h
index 91325ce4e7..554f293aad 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -28,8 +28,8 @@
 #include "libavutil/version.h"
 
 #define LIBAVCODEC_VERSION_MAJOR  59
-#define LIBAVCODEC_VERSION_MINOR   3
-#define LIBAVCODEC_VERSION_MICRO 102
+#define LIBAVCODEC_VERSION_MINOR   4
+#define LIBAVCODEC_VERSION_MICRO 100
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
                                                LIBAVCODEC_VERSION_MINOR, \