avformat: add fields to AVProgram/AVStream for PMT change tracking

These fields will allow the mpegts demuxer to expose details about
the PMT/program which created the AVProgram and its AVStreams.

In mpegts, a PMT which advertises streams has a version number
which can be incremented at any time. When the version changes,
the pids which correspond to each of it's streams can also change.

Since ffmpeg creates a new AVStream per pid by default, an API user
needs the ability to (a) detect when the PMT changed, and (b) tell
which AVStream were added to replace earlier streams.

This has been a long-standing issue with ffmpeg's handling of mpegts
streams with PMT changes, and I found two related patches in the wild
that attempt to solve the same problem:

The first is in MythTV's ffmpeg fork, where they added a
void (*streams_changed)(void*); to AVFormatContext and call it from
their fork of the mpegts demuxer whenever the PMT changes.

The second was proposed by XBMC in
https://ffmpeg.org/pipermail/ffmpeg-devel/2012-December/135036.html,
where they created a new AVMEDIA_TYPE_DATA stream with id=0 and
attempted to send packets to it whenever the PMT changed.

Signed-off-by: Aman Gupta <aman@tmm1.net>

1 files changed, 8 insertions, 0 deletions

diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index 6dce88fad5..ade918f99c 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -1103,6 +1103,13 @@ typedef struct AVStream {
      */
     int stream_identifier;
 
+    /**
+     * Details of the MPEG-TS program which created this stream.
+     */
+    int program_num;
+    int pmt_version;
+    int pmt_stream_idx;
+
     int64_t interleaver_chunk_size;
     int64_t interleaver_chunk_duration;
 
@@ -1260,6 +1267,7 @@ typedef struct AVProgram {
     int program_num;
     int pmt_pid;
     int pcr_pid;
+    int pmt_version;
 
     /*****************************************************************
      * All fields below this line are not part of the public API. They