[linux-dvb] Trouble with tuning on Lifeview FlyDVB-T

BOUWSMA Barry freebeer.bouwsma at gmail.com
Fri Oct 3 21:15:04 CEST 2008


On Wed, 1 Oct 2008, Lee Jones wrote:

> all the responses. FIrst of alll what does "PID" stand for?

As I have used it, it is the numbers used to identify the
video and audio streams that can be found highlighted
below.

As for what it means, rather than post bogus information
from the top of my head, you can probably learn more
details than you want, by searching for MPEG Transport
Stream Audio Video PID or something similar.


> btw, first of all here's the tuning details that w_scan originally found;

Thanks.  Now I owe it to everyone to figure out exactly
what w_scan is and how it differs from my hacked `scan'...


> # T freq bw fec_hi fec_lo mod transmission-mode guard-interval hierarchy
> T 530000000 8MHz AUTO AUTO AUTO AUTO AUTO NONE
> T 562000000 8MHz AUTO AUTO AUTO AUTO AUTO NONE
> T 570000000 8MHz AUTO AUTO AUTO AUTO AUTO NONE

Hmmm, that's it?  You seem to be missing a few of the
frequencies, like half of them, posted in my earlier
reply, sent from this transmitter...

What is interesting to me is that the missing freqs
all have a negative offset (490, 546, & 514MHz nominal)
so perhaps this scan can handle no-offset 530 and the
+1/6MHz offsets of 562 and 570MHz.


You posted earlier some `tzap' signal-strength and bit-
error-rate values.  You also said your other DVB-T card
received all stations without problems.  Do you see similar
error rates, or even better, from this other card?

I can't say anything about the signal strength, as there
is no fixed reference against which all linux drivers are
calibrated, but `9e' is near the middle of the range
between `00' and `ff'.

It's possible there's a sensitivity problem that needs to
be tweaked by the driver (a LNA or something).

(Let me connect a simple short antenna and see how one of
my tuner cards works against two line-of-sight transmitters
within my Faraday-cage-type room.  Hmmm.  Oh yes.  Oh, yes!)

At least for me, `ff' means no useful signal, `9x' has a
few errors, and I do well at `7x'.  My BER rate is zero,
except when I have a horribly weak signal.  Ooh, that one
blasts in compared with the others.  So why did my recent
recording of that frequency with an amplified yagi get all
messed up?  Hmmm...

You didn't say anything about your distance from the
transmitter, the terrain, and so on -- given that the services
I receive all post-DSO and are full-strength, while you are
receiving a lower-power signal until your DSO, I'd like to
see the `tzap' output from each of the six frequencies with
your other card, if possible.

By me, I can get `ffff' for SNR and uncorrected BER of 0
with a simple stub of an antenna, and I would hope you would
see the same.


> And a few lines from channels.conf,  generated by scan;
> ITV1:530000000:INVERSION_AUTO:BANDWIDTH_8_MHZ:FEC_AUTO:FEC_AUTO
 [snip]:GUARD_INTERVAL_AUTO:HIERARCHY_NONE:520:521:8270
                                           ^^^ ^^^
I've highlighted the video and audio PIDs respectively above
(fixed-width font of course).
  

> BBC FOUR:562000000:INVERSION_AUTO:BANDWIDTH_8_MHZ:FEC_AUTO:FEC_AUTO:QAM_AUTO:TRANSMISSION_MODE_AUTO:
 GUARD_INTERVAL_AUTO:HIERARCHY_NONE:0:0:16832
                                    ^ ^
As this scan was done sometime in the day (before 19h your-
time), you don't get the BBC Four PIDs -- as was noted by
another poster, these are shared with CBeebies, for which
you will (should!) have obtained correct values.


> And I'm guessing this is Mux B (C34); not sure though!

> 0x0000 0x41c0: pmt_pid 0x02be BBC -- BBC FOUR (running)
> 0x0000 0x4240: pmt_pid 0x02bf BBC -- CBeebies (running)

No problems tuning.  Interesting, though -- by satellite,
the status of BBC3/4 CBBC/CBeebies is such that by day,
the first two are tagged as `(not running)', and by night,
the latter two...

In any case, you should be able to ``tune'' into BBC4 by
instead tuning to CBeebies after 19h.  Or you can permanently
fix this by copying the PID values from CBeebies by day to
the 0-values of BBC4 -- repeat for CBBC and BBC3.  Doing so
will give you the correct Service ID (following the video+
audio PIDs).


> I hope that is the correct infos!

Close enough  ;-)

First question:  if you download the latest tuning file from
../HG-src/dvb-apps/util/scan/dvb-t/uk-Rowridge
are you able to receive all six frequencies with both cards?

Second:  How do the `tzap' values for both cards for all
frequencies compare, with the same aerial input -- in particular,
the signal strength, BER, and SNR values?


barry bouwsma



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