[linux-dvb] How to determine the frequency of a channel

[Martin Neuditschko <yosuke.tomoe@gmx.net>]

Hi!

I tried to determine the best frequency for a channel.
So I am using Newstruct drivers (02.07.02) and changed czap.c so that
the frequency from the channels file +/-250000 Hz is used (in 100 Hz steps)
and that each of this frequencies is tried to be set for 20 times (see
check_frontend):

-----------------------------------------
|static
|int check_frontend (void)
|{
|   int fd, i=0;
|   FrontendStatus status;
|   uint16_t snr, signal;
|   uint32_t ber, uncorrected_blocks;
|
|   if ((fd = open (FRONTEND_DEV, O_RDWR)) < 0) {
|      fprintf (stderr, "failed opening '%s' !!!\n", FRONTEND_DEV);
|      return -1;
|   }
|
|   do {
|      ioctl (fd, FE_READ_STATUS, &status);
|      ioctl (fd, FE_READ_SIGNAL_STRENGTH, &signal);
|      ioctl (fd, FE_READ_SNR, &snr);
|      ioctl (fd, FE_READ_BER, &ber);
|      ioctl (fd, FE_READ_UNCORRECTED_BLOCKS, &uncorrected_blocks);
|
|      printf ("status %02x | signal %04x | snr %04x | ber %08x | unc %08x | ",
|              status, signal, snr, ber, uncorrected_blocks);
|      if (status & FE_HAS_LOCK)
|         printf ("FE_HAS_LOCK");
|      printf ("\n");
|      usleep (1000000);
|   /* } while (1 || !(status & FE_HAS_LOCK)); */
|      i++;
|   } while (i<20);
|
|   close (fd);
|   return 0;
|}
|
|int main (int argc, char **argv)
|{
|   struct dvb_frontend_parameters frontend;
|   int vpid, apid;
|   unsigned int freq, f;
|
|   if (argc != 2) {
|      printf ("\n\tusage: %s <channel name>\n\n", argv[0]);
|      exit (-1);
|   }
|
|   memset (&frontend, 0, sizeof(struct dvb_frontend_parameters));
|
|   if (parse (CHANNEL_FILE, argv[1], &frontend, &vpid, &apid))
|      return -1;
|
|   freq = frontend.frequency;
|   for (f = freq - 250000; f <= freq + 250000; f += 100)
|   {
|     frontend.frequency = f;
|     printf( "Frequency: %u\n", frontend.frequency );
|     setup_frontend (&frontend);
|     setup_demux (vpid, apid);
|
|     check_frontend ();
|   }
|   return 1;
|}
-----------------------------------------

But the result is not which I wanted because the "FE_HAS_LOCK"
appears very often but there is no audio or video.

Here a small example:
Frequency: 377758000
status 00 | signal 9090 | snr d6d6 | ber 00012eec | unc 0000007f |
status 1f | signal ffff | snr eded | ber 00012eec | unc 0000007f | FE_HAS_LOCK
status 1f | signal ffff | snr ecec | ber 0002c3d8 | unc 00000000 | FE_HAS_LOCK
status 1f | signal ffff | snr eded | ber 0002c3d8 | unc 00000003 | FE_HAS_LOCK
status 1f | signal ffff | snr ebeb | ber 00013335 | unc 00000000 | FE_HAS_LOCK
status 1f | signal ffff | snr ecec | ber 00013451 | unc 00000002 | FE_HAS_LOCK
status 1f | signal ffff | snr eded | ber 00013451 | unc 00000000 | FE_HAS_LOCK
status 1f | signal ffff | snr ecec | ber 00013057 | unc 00000000 | FE_HAS_LOCK
status 1f | signal ffff | snr ecec | ber 00013057 | unc 00000004 | FE_HAS_LOCK
status 1f | signal ffff | snr eeee | ber 00012f50 | unc 00000002 | FE_HAS_LOCK
status 1f | signal ffff | snr ebeb | ber 0001316d | unc 00000001 | FE_HAS_LOCK
status 1f | signal ffff | snr ecec | ber 0001316d | unc 00000001 | FE_HAS_LOCK
status 1f | signal ffff | snr ecec | ber 0001345f | unc 00000000 | FE_HAS_LOCK
status 1f | signal ffff | snr ecec | ber 0001345f | unc 00000001 | FE_HAS_LOCK
status 1f | signal ffff | snr ecec | ber 0001318e | unc 00000000 | FE_HAS_LOCK
status 1f | signal ffff | snr ebeb | ber 0001332a | unc 00000000 | FE_HAS_LOCK

How else could I try to determine the best frequency?
Has someone an idea?

best regards
Martin Neuditschko


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