avformat/hls: Fix probing mpegts audio streams that use probing

Commit 04964ac311 ("avformat/hls: Fix missing streams in some
cases with MPEG TS") caused a regression where subdemuxer streams that
use probing (e.g. dts/eac3/mp2 in mpegts) no longer get probed properly.

This is because the codec parameters from the subdemuxer stream, once
probed, are not passed on to the main stream.

Fix that by updating the codec parameters if the codec id changes.

Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
(cherry picked from commit 3d2f636497)

libavformat/hls.c

@@ -1536,6 +1536,8 @@ static void set_stream_info_from_input_stream(AVStream *st, struct playlist *pls
         avpriv_set_pts_info(st, 33, 1, MPEG_TIME_BASE);
     else
         avpriv_set_pts_info(st, ist->pts_wrap_bits, ist->time_base.num, ist->time_base.den);
+
+    st->internal->need_context_update = 1;
 }
 
 /* add new subdemuxer streams to our context, if any */
@@ -1950,6 +1952,8 @@ static int hls_read_packet(AVFormatContext *s, AVPacket *pkt)
     /* If we got a packet, return it */
     if (minplaylist >= 0) {
         struct playlist *pls = c->playlists[minplaylist];
+        AVStream *ist;
+        AVStream *st;
 
         ret = update_streams_from_subdemuxer(s, pls);
         if (ret < 0) {
@@ -1972,15 +1976,23 @@ static int hls_read_packet(AVFormatContext *s, AVPacket *pkt)
             return AVERROR_BUG;
         }
 
+        ist = pls->ctx->streams[pls->pkt.stream_index];
+        st = pls->main_streams[pls->pkt.stream_index];
+
         *pkt = pls->pkt;
-        pkt->stream_index = pls->main_streams[pls->pkt.stream_index]->index;
+        pkt->stream_index = st->index;
         reset_packet(&c->playlists[minplaylist]->pkt);
 
         if (pkt->dts != AV_NOPTS_VALUE)
             c->cur_timestamp = av_rescale_q(pkt->dts,
-                                            pls->ctx->streams[pls->pkt.stream_index]->time_base,
+                                            ist->time_base,
                                             AV_TIME_BASE_Q);
 
+        /* There may be more situations where this would be useful, but this at least
+         * handles newly probed codecs properly (i.e. request_probe by mpegts). */
+        if (ist->codecpar->codec_id != st->codecpar->codec_id)
+            set_stream_info_from_input_stream(st, pls, ist);
+
         return 0;
     }
     return AVERROR_EOF;