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List:       xine-devel
Subject:    [xine-devel] [patch] Fix video pid misdetection
From:       Andrew de Quincey <adq_dvb () lidskialf ! net>
Date:       2007-06-02 20:14:50
Message-ID: 20070602211450.xvh5mxuggskwwoo0 () lidskialf ! net
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Hi, the next bug that has been annoying me is as follows.

I have some streams recorded from BBC4 on UK DVB-T. BBC4 only actually
starts transmitting at about 7pm; prior to that there is a static
picture saying it is not playing just now. With these streams and
xine, I would get audio, but no picture.

Looking at the PMT table during the static picture, all the streams
have type 0x0b. However there IS a video stream in there, but there
are also several streams of binary data.

Xine's current video PID auto-detection code was locking on to one of
these streams of binary data because it contained the magic sequence
00 00 01 e0 at one of the PUS. *HOWEVER* it is NOT a PES stream; this
sequence is just an accident. The other problem is that xine can only
handle one video stream; so once it was misdetected once, it was stuck
at that PID.

The attached patch changes the corrupted_pes flag into a counter. If a
video stream has more than CORRUPT_PES_THRESHOLD corrupt PES packets
in a row, then it is deselected as the video stream, and
auto-detection is kicked off again. Auto-detection will now also
ignore any streams seen previously which have a nonzero corrupted_pes
count. This works very well; I can now see the video fine.

One possible issue might be that if you get a lot of corrupt PES in a
stream which really IS the video stream, it will be deselected.
However, this is not actually a problem: once the corruption goes
away, the corrupted_pes counter will be reset to 0, and the stream
will once again be autodetected as the video stream (and playback will
continue from there).



["xine-1.1.6-pidfix.patch" (text/x-diff)]

diff -Naur xine-lib-1.1.6.ORIG/src/demuxers/demux_ts.c xine-lib-1.1.6.PIDFIX/src/demuxers/demux_ts.c
--- xine-lib-1.1.6.ORIG/src/demuxers/demux_ts.c	2007-04-17 02:00:50.000000000 +0100
+++ xine-lib-1.1.6.PIDFIX/src/demuxers/demux_ts.c	2007-06-02 20:37:48.367235323 +0100
@@ -180,6 +180,8 @@
 
 #define MAX_PES_BUF_SIZE 2048
 
+#define CORRUPT_PES_THRESHOLD 10
+
 #define NULL_PID 0x1fff
 #define INVALID_PID ((unsigned int)(-1))
 #define INVALID_PROGRAM ((unsigned int)(-1))
@@ -910,12 +912,17 @@
      m->buf = m->fifo->buffer_pool_alloc(m->fifo);
 
     if (!demux_ts_parse_pes_header(this->stream->xine, m, ts, len, this->stream)) {
-      m->corrupted_pes = 1;
       m->buf->free_buffer(m->buf);
       m->buf = NULL;
-      xprintf(this->stream->xine, XINE_VERBOSITY_DEBUG, 
+      
+      if (m->corrupted_pes > CORRUPT_PES_THRESHOLD) {
+        if (this->videoPid == m->pid)
+          this->videoPid = INVALID_PID;
+      } else {
+        m->corrupted_pes++;
+        xprintf(this->stream->xine, XINE_VERBOSITY_DEBUG, 
 	      "demux_ts: PID 0x%.4x: corrupted pes encountered\n", m->pid);
-
+      }
     } else {
 
       m->corrupted_pes = 0;
@@ -1785,13 +1792,27 @@
     
     if ( (pes_stream_id >= VIDEO_STREAM_S) && (pes_stream_id <= VIDEO_STREAM_E) ) {
       if ( this->videoPid == INVALID_PID) {
-
-	xprintf (this->stream->xine, XINE_VERBOSITY_DEBUG, 
-		 "demux_ts: auto-detected video pid 0x%.4x\n", pid);
-
-	this->videoPid = pid;
-	this->videoMedia = this->media_num;
-	demux_ts_pes_new(this, this->media_num++, pid, this->video_fifo, pes_stream_id);
+        int i, found = 0;
+        for(i = 0; i < this->media_num; i++) {
+          if (this->media[i].pid == pid) {
+            found = 1;
+            break;
+          }
+        }
+        
+        if (found && (this->media[i].corrupted_pes == 0)) {
+          this->videoPid = pid;
+	  this->videoMedia = i;
+        } else if (!found) {
+	  this->videoPid = pid;
+	  this->videoMedia = this->media_num;
+	  demux_ts_pes_new(this, this->media_num++, pid, this->video_fifo, pes_stream_id);
+        }
+        
+        if (this->videoPid != INVALID_PID) {
+          xprintf (this->stream->xine, XINE_VERBOSITY_DEBUG, 
+                   "demux_ts: auto-detected video pid 0x%.4x\n", pid);
+        } 
       }
     } else if ( (pes_stream_id >= AUDIO_STREAM_S) && (pes_stream_id <= AUDIO_STREAM_E) ) {
        if (this->audio_tracks_count < MAX_AUDIO_TRACKS) {


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