[FFmpeg-devel,v3,2/5] avformat: add av_program_copy()

diff --git a/doc/APIchanges b/doc/APIchanges
index 889f9925b1..2588c17560 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -2,6 +2,9 @@  The last version increases of all libraries were on 2023-02-09
 
 API changes, most recent first:
 
+2023-02-xx - xxxxxxxxxx - lavf 60.4.100 - avformat.h
+  Add av_program_copy()
+
 2023-02-xx - xxxxxxxxxx - lavf 60.3.100 - avformat.h
   Add av_program_add_stream_index2().
 
diff --git a/libavformat/avformat.c b/libavformat/avformat.c
index 0f203e4f86..64741b6f4a 100644
--- a/libavformat/avformat.c
+++ b/libavformat/avformat.c
@@ -369,6 +369,72 @@  void av_program_add_stream_index(AVFormatContext *ac, int progid, unsigned idx)
     return;
 }
 
+int av_program_copy(AVFormatContext *dst, const AVFormatContext *src, int progid, int overwrite)
+{
+    const AVProgram *src_prog = NULL;
+    AVProgram *dst_prog = NULL;
+    int ret, idx = -1;
+
+    for (unsigned i = 0; i < src->nb_programs; i++)
+        if (src->programs[i]->id == progid)
+            src_prog = src->programs[i];
+
+    if (!src_prog) {
+        av_log(dst, AV_LOG_ERROR, "source program not found: id=0x%04x\n", progid);
+        return AVERROR(EINVAL);
+    }
+
+    for (unsigned i = 0; i < dst->nb_programs; i++) {
+        if (dst->programs[i]->id == progid)
+            idx = i;
+    }
+
+    if (idx >= 0 && !overwrite) {
+        av_log(dst, AV_LOG_WARNING, "target muxer already has program with id=0x%04x; not overwriting\n", progid);
+        return 0;
+    }
+
+    av_log(dst, AV_LOG_TRACE, "%s program: id=0x%04x\n", idx >= 0 ? "overwriting" : "copying", progid);
+
+    if (idx >= 0) {
+        dst_prog = dst->programs[idx];
+        av_dict_free(&dst_prog->metadata);
+        av_freep(&dst_prog->stream_index);
+        dst_prog->nb_stream_indexes = 0;
+    } else {
+        dst_prog = av_mallocz(sizeof(*dst_prog));
+        if (!dst_prog)
+            return AVERROR(ENOMEM);
+        ret = av_dynarray_add_nofree(&dst->programs, &dst->nb_programs, dst_prog);
+        if (ret < 0) {
+            av_free(dst_prog);
+            return ret;
+        }
+    }
+
+    /* public fields */
+    dst_prog->id          = src_prog->id;
+    dst_prog->flags       = src_prog->flags;
+    dst_prog->discard     = src_prog->discard;
+    dst_prog->program_num = src_prog->program_num;
+    dst_prog->pmt_pid     = src_prog->pmt_pid;
+    dst_prog->pcr_pid     = src_prog->pcr_pid;
+    dst_prog->pmt_version = src_prog->pmt_version;
+
+    for (unsigned i = 0; i < dst->nb_streams; i++) {
+        for (unsigned j = 0; j < src_prog->nb_stream_indexes; j++)
+            if (dst->streams[i]->id == src->streams[src_prog->stream_index[j]]->id) {
+                if (ret = av_program_add_stream_index2(dst, dst_prog->id, i) < 0)
+                    return ret;
+            }
+    }
+
+    if (ret = av_dict_copy(&dst_prog->metadata, src_prog->metadata, 0) < 0)
+        return ret;
+
+    return 0;
+}
+
 AVProgram *av_find_program_from_stream(AVFormatContext *ic, AVProgram *last, int s)
 {
     for (unsigned i = 0; i < ic->nb_programs; i++) {
diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index 33ab0bc8ba..46b4d177c3 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -1886,6 +1886,28 @@  uint8_t *av_stream_get_side_data(const AVStream *stream,
 
 AVProgram *av_new_program(AVFormatContext *s, int id);
 
+/**
+ * Copy an AVProgram from one AVFormatContext to another.
+ *
+ * Streams in the destination context whose IDs match the IDs of the streams in the
+ * source AVProgram index are added to the stream index of the copied AVProgram.
+ *
+ * If a new program has to be added, the function expects and requires any existing buffer
+ * holding the array of pointers to AVPrograms in the destination context to have its size
+ * be a power-of-two value. This should be the case if all earlier programs were created
+ * using av_new_program or this function. 
+ *
+ * @param dst           pointer to the target muxer context
+ * @param src           pointer to the source muxer context
+ * @param progid        ID of the program to be copied
+ * @param overwrite     whether to overwrite if target muxer already
+ *                      contains a program with the same ID
+ *
+ * @return  >= 0 in case of success, a negative AVERROR code in case of
+ *          failure
+ */
+int av_program_copy(AVFormatContext *dst, const AVFormatContext *src, int progid, int overwrite);
+
 /**
  * @}
  */
diff --git a/libavformat/version.h b/libavformat/version.h
index 7ff1483912..62fa908659 100644
--- a/libavformat/version.h
+++ b/libavformat/version.h
@@ -31,7 +31,8 @@ 
 
 #include "version_major.h"
 
-#define LIBAVFORMAT_VERSION_MINOR   3
+#define LIBAVFORMAT_VERSION_MINOR   4
+
 #define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \