stream_dvb: Also demux PMT if possible, reactivate TPID parsing.

If VDR-channel-config is used, we know the service_id.
Using that, PMT can be extracted from PAT (code for that
inspired by szap-s2 again).
For this, we need to demux PAT with a special filter-setup,
and once PMT was found it can be added to the PID-list.
PMT is only resolved the first time one tunes to a channel,
then stored in the channel-list in memory.

With PMT available, ffmpeg can safely decode the teletext-pids.

stream/dvb_tune.c

@@ -187,6 +187,74 @@ int dvb_set_ts_filt(dvb_priv_t *priv, int fd, uint16_t pid, dmx_pes_type_t pesty
         return 1;
 }
 
+int dvb_get_pmt_pid(dvb_priv_t *priv, int card, int service_id) {
+  /* We need special filters on the demux, 
+     so open one locally, and close also here. */
+  char demux_dev[32];
+  sprintf(demux_dev, "/dev/dvb/adapter%d/demux0", card);
+  
+  struct dmx_sct_filter_params fparams;
+  
+  memset(&fparams, 0, sizeof(fparams));
+  fparams.pid = 0;
+  fparams.filter.filter[0] = 0x00;
+  fparams.filter.mask[0] = 0xff;
+  fparams.timeout = 0;
+  fparams.flags = DMX_IMMEDIATE_START | DMX_CHECK_CRC;
+
+  int pat_fd;
+  if ((pat_fd = open(demux_dev, O_RDWR)) < 0) {
+    MP_ERR(priv, "Opening PAT DEMUX failed, error: %d", errno);
+    return -1;
+  }
+  
+  if (ioctl(pat_fd, DMX_SET_FILTER, &fparams) == -1) {
+    MP_ERR(priv, "ioctl DMX_SET_FILTER failed, error: %d", errno);
+    close(pat_fd);
+    return -1;
+  }
+    
+  int bytes_read;
+  int section_length;
+  unsigned char buft[4096];
+  unsigned char *bufptr = buft;
+
+  int pmt_pid = -1;
+
+  bool pat_read = false;
+  while (!pat_read) {
+    if (((bytes_read = read(pat_fd, bufptr, sizeof(buft))) < 0) && errno == EOVERFLOW)
+      bytes_read = read(pat_fd, bufptr, sizeof(buft));
+    if (bytes_read < 0) {
+      MP_ERR(priv, "PAT: read_sections: read error: %d", errno);
+      close(pat_fd);
+      return -1;
+    }
+    
+    section_length = ((bufptr[1] & 0x0f) << 8) | bufptr[2];
+    if (bytes_read != section_length + 3) {
+      continue;
+    }
+    
+    bufptr += 8;
+    section_length -= 8;
+    
+    /* assumes one section contains the whole pat */
+    pat_read = true; 
+    while (section_length > 0) {
+      int this_service_id = (bufptr[0] << 8) | bufptr[1];
+      if (this_service_id == service_id) {
+        pmt_pid = ((bufptr[2] & 0x1f) << 8) | bufptr[3];
+        section_length = 0;
+      }
+      bufptr += 4;
+      section_length -= 4;
+    }
+  }
+  close(pat_fd);
+  
+  return pmt_pid;
+}
 
 int dvb_demux_stop(int fd)
 {