mpegts-mythtv.c: reuse existing streams for MHEG

This should emulate the prior behavior before harmonization of
removing and adding new streams.

My sample now only has two MHEG streams, one for each PID,
as it used to.

In the process, inline new_section_av_stream to ensure the values
are always set correctly.

I don't know if this is the correct way to reuse the streams,
but it appears to work correctly.

mythtv/external/FFmpeg/libavformat/mpegts-mythtv.c

@@ -2452,27 +2452,6 @@ static int is_desired_stream(enum AVMediaType codec_type, enum AVCodecID codec_i
     return val;
 }
 
-static AVStream *new_section_av_stream(SectionContext *sect, enum AVMediaType type,
-                                       enum AVCodecID id)
-{
-    sect->st = avformat_new_stream(sect->stream, NULL);
-    if (!(sect->st)) {
-        av_log(sect->ts, AV_LOG_ERROR, "Cannot allocate memory.\n");
-        return NULL;
-    }
-
-    sect->st->id = sect->pid;
-
-    avpriv_set_pts_info(sect->st, 33, 1, 90000);
-
-    sect->st->codecpar->codec_type = type;
-    sect->st->codecpar->codec_id   = id;
-    sect->st->priv_data = sect;
-    sect->st->need_parsing = AVSTREAM_PARSE_NONE;
-
-    return sect->st;
-}
-
 static SectionContext *add_section_stream(MpegTSContext *ts, int pid, int stream_type)
 {
     MpegTSFilter *tss = ts->pids[pid];
@@ -2784,6 +2763,8 @@ static void pmt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
         if (stream_type == STREAM_TYPE_DSMCC_B)
         {
             SectionContext *sect = NULL;
+            int idx = -1;
+
             sect = add_section_stream(ts, pid, stream_type);
             if (!sect)
             {
@@ -2793,14 +2774,29 @@ static void pmt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
                 goto out;
             }
 
-            st = new_section_av_stream(sect, AVMEDIA_TYPE_DATA, AV_CODEC_ID_DSMCC_B); // values from ISO_types
-            if (!st)
-            {
-                av_log(ts, AV_LOG_ERROR, "mpegts_add_stream: "
-                       "error creating A/V stream for pid 0x%x with type %i\n",
-                       pid, stream_type);
+            idx = ff_find_stream_index(ts->stream, pid);
+            if (idx >= 0) {
+                st = ts->stream->streams[idx];
+                av_log(ts, AV_LOG_DEBUG, "mpegts_add_stream: "
+                   "reusing stream #%d, has id 0x%x and codec %s, type %s at 0x%p\n",
+                   st->index, st->id, avcodec_get_name(st->codecpar->codec_id),
+                   av_get_media_type_string(st->codecpar->codec_type), st);
+            }
+            if (!st) {
+                st = avformat_new_stream(sect->stream, NULL);
+            }
+            if (!st) {
                 goto out;
             }
+            sect->st = st;
+            sect->st->id = sect->pid;
+
+            avpriv_set_pts_info(sect->st, 33, 1, 90000);
+
+            sect->st->codecpar->codec_type = AVMEDIA_TYPE_DATA;
+            sect->st->codecpar->codec_id   = AV_CODEC_ID_DSMCC_B;
+            sect->st->priv_data = sect;
+            sect->st->need_parsing = AVSTREAM_PARSE_NONE;
 
             av_log(ts, AV_LOG_DEBUG, "mpegts_add_stream: "
                    "stream #%d, has id 0x%x and codec %s, type %s at 0x%p\n",