[linux-dvb] dvb-t config for Ukraine_Kiev (ua)

BOUWSMA Barry freebeer.bouwsma at gmail.com
Fri Jan 9 10:54:37 CET 2009


Hello Dmitry, I hope you are able to keep warm this winter :-)

I am sending a copy of my reply to several of your messages to
the mailing list, in case someone else is able to help, and in
the unlikely event that what I write might be useful to someone
else.  I hope that is okay for you...


On Tue, 30 Dec 2008, Dmitry Podyachev wrote:

> p.s.:  what is the SFN ?

To give a bit of context to this question, I had read that some
of the frequencies in use in Kiev/Kиïв were part of a Single-
Frequency Network (SFN).  That is where the same frequency is
used by several transmitters relatively close to each other to
cover a larger area than can be reached from a single site.

This works because one of the features of DVB-T is the Guard
Interval, which allows the receiver to make use of reflections,
echoes, multipath interference, or for a SFN, signals received
from additional transmitters which appear as a long echo.

I am not an expert on this, but as I understand it, the maximum
distance between separate transmitters on the same frequency
which send the same programmes is determined by the guard
interval.  In countries where use is made of a Multiple-Frequency
Network (MFN) such as France for the most part, the smallest
guard interval is used, allowing for a higher available bitrate
from the 8MHz channel bandwidth, with the drawback that there
are more frequencies in use, and it is likely that one can
receive the same programming two or three or more times in one
location between different transmitters.

In contrast, in Germany (see the de-BW list which I posted to
this mailing list some weeks or months ago), the same frequency
is in use at several widely-spaced transmitters, but not so far
apart that one cannot receive more than one at some locations.
For this, a guard interval is chosen that is much larger, say,
1/4 instead of 1/32, but this also means that less overall
bitrate is available on a particular 8MHz channel.

Hinted at in the de-BW list is that in Switzerland use is also
made of several SFNs, consisting there of some higher-power
transmitters on a particular frequency, supplemented by many
lower-power transmitters on the order of kilowatts, due to
the terrain making it difficult to cover the many valleys that
the high-power transmitter fails to reach.  The large number
of filler transmitters makes it impractical to list them all
with the redundant info in the way that I did in de-BW, though
a list can be downloaded in case specific information is needed
to properly site a receiving antenna.


With analogue broadcasting, this SFN use was not possible, as
more than one transmitter on the same frequency results in
the familiar interference that could be seen where multiple
low-power filler transmitters were received.

For readers in ATSC-land, this can be a difficult concept to
grasp, as for the most part, all stations are independent of
each other and use a single high-power transmitting site, so
as I understand from reading gripes on Slashdot (which is the
closest I care to come to understanding details of ATSC), there
is no provision made for handling multiple transmitters, and as
a result, multipath interference or other echo sources, and
reception is nowhere near as robust as the case I've experienced
where a virtually unwatchable analogue frequency is turned into
a clear DVB-T signal, and a literally unwatchable frequency is
turned into mostly-clear DVB-T.  That is, for US-types, there
is no concept of a national broadcaster (with, say, vague
tuning info, like, `97 to 99 FM' as opposed to a specific
frequency, `88.3 on your FM dial').  But I digress...


Anyway, a guard interval of 1/32 would be used by a single
transmitter, or perhaps two closeby transmitters on the same
frequency, whereas for a Single-Frequency Network (SFN), I
would expect to see a different value, depending on the size
of the coverage area, like 1/8 as in Paris, or 1/4 as used
for the national and regional broadcasters in Germany.  This
is why I was somewhat confused by the conflict of seeing the
use of SFN to refer to Kiev, while seeing 1/32 given as a
guard interval.  But I am completely unfamiliar with the
DVB-T network in and near Kiev or throughout the Ukraine.


That was much more than I needed to write about that...


On Thu, 8 Jan 2009, Dmitry Podyachev wrote:

> Dear Barry,
> Happy New Year and Merry Christmas!
> Hope you are ok.

Thank you, and the same to you!

> Could you help me with advice about dvb-t?
> I try to play something from it, but nothing:
> 
> scan -q -5 -a 0 -u -x 0 ua >/home/iptv/.mplayer/channels.conf

> cat /home/iptv/.mplayer/channels.conf
> UT-1:634000000:INVERSION_AUTO:BANDWIDTH_8_MHZ:FEC_AUTO:FEC_AUTO:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_AUTO:HIERARCHY_NONE:4111:4112:1
> RADA:634000000:INVERSION_AUTO:BANDWIDTH_8_MHZ:FEC_AUTO:FEC_AUTO:QAM_64:TRANSMISSION_MODE_8K:GUARD_INTERVAL_AUTO:HIERARCHY_NONE:4131:4132:3

This shows that you were able to able to tune with success to
634MHz and list the available programmes, so at least `scan'
was able to lock onto that frequency with the given parameters.
(the other available frequencies were listed in your following
message)


> mplayer -vo caca -cache 2222 dvb://"RADA"
> 
> Playing dvb://RADA.
> dvb_tune Freq: 634000000
> Not able to lock to the signal on the given frequency, timeout: 30
> dvb_tune, TUNING FAILED

However, for some reason, `mplayer' was not able to lock onto
the same frequency.

> the detailed info here:
[much snipped]
> CONFIG_READ FILE: /home/iptv/.mplayer/channels.conf, type: 2
> TER, NUM: 0, NUM_FIELDS: 11, NAME: UT-1, FREQ: 634000000 PIDS:  4111  4112  0
> TER, NUM: 1, NUM_FIELDS: 11, NAME: RADA, FREQ: 634000000 PIDS:  4131  4132  0
> TER, NUM: 2, NUM_FIELDS: 11, NAME: 5 KANAL, FREQ: 650000000 PIDS:  4311  4312
> 0

> OPEN_DVB: prog=RADA, card=1, type=2, vid=0, aid=0
> dvb_streaming_start(PROG: RADA, CARD: 1, VID: 0, AID: 0, TYPE: , FILE: (null))
> PROGRAM NUMBER 1: name=RADA, freq=634000000

> DVB_SET_CHANNEL: new channel name=RADA, card: 0, channel 1
> DIFFERENT TUNING THAN THE PREVIOUS:   -> 0|634000000|2|0|9|3|1|3
> dvb_tune Freq: 634000000
> TUNE_IT, fd_frontend 3, fd_sec 0
> freq 634000000, srate 4, pol ?, tone -1220478728, specInv, diseqc 3074488576,

In this verbose output from `mplayer', the frequency is correct,
while the other strange values are only relevant for satellite
DVB-S, and can probably be ignored...


> fe_modulation_t modulation,fe_code_rate_t HP_CodeRate, fe_transmit_mode_t
> TransmissionMode,fe_guard_interval_t guardInterval, fe_bandwidth_t bandwidth

I am not sure if the lack of any values here means anything,
because I've never needed to debug DVB-T tuning with `mplayer',
as it has ``just worked'' for me...


> Using DVB card "Philips TDA10046H DVB-T"
> *tuning DVB-T to 634000000 Hz, bandwidth: 0

The `bandwidth' value seems wrong, while it is correct in the
tuning file above, but that may not mean anything...


> Getting frontend status
> Not able to lock to the signal on the given frequency, timeout: 30



> p.s. How you play or stream from dvb-t ?
> I try dvbstream, but the same:
> dvbstream -c 0 -I 2 -qam 64 -gi 32 -cr 2_3 -bw 8 -f 650000000 -net
> 224.12.12.12:1234 4311 4312

> Tuning to 650000000 Hz
> Using DVB card "Philips TDA10046H DVB-T", freq=650000000
> tuning DVB-T (in United Kingdom) to 650000000 Hz, Bandwidth: 8
> *Getting frontend status
> Not able to lock to the signal on the given frequency

Again, there is some problem being able to lock onto this
frequency.  Which seems strange, because `scan' appeared to
be able to list the services.

However, this might be easier -- at least in my outdated
`dvbstream' the default FFT transmission mode is 2k, while
it should be specified as 8k for Kiev, so you will need to
add `-tm 8' to your above command line.

Try that and see if it works...


The other parameters seem to be correct, at least as seen
in a quick g00gle result:
   paбoтaeт в ДMB-диaпaзoнe нa 51 TBK 714 MΓц,
   мoщнocть дo 1 ĸBт;
   пapaмeтpы COFDM мoдyляции: 64-QAM, FFT 8K, Code Rate 2/3,
   Guard Intervals 1/32, Bandwidth 8 MΓц.

If you edit your channels.conf file to use these values
at 714MHz for channels
   51 | 714,0 | KΓTPK, 1+1, 24, Toниc, Kyльтypa,
   Enter-φильм, УP-1, УP-2/Πpoминь,
   УP-3/Kyльтypa
in place of `AUTO' and try that, maybe that will work.

I think there are some tuners that require specific values
and will not work with `AUTO', although there are many that
will work...


hope this is helpful
barry bouwsma
some random 8-bit chars to make sure this gets tagged as utf-8...
„…™ψöžא



More information about the linux-dvb mailing list