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 tothe mailing list, in case someone else is able to help, and inthe unlikely event that what I write might be useful to someoneelse. 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 someof the frequencies in use in Kiev/Kиïв were part of a Single-Frequency Network (SFN). That is where the same frequency isused by several transmitters relatively close to each other tocover a larger area than can be reached from a single site. This works because one of the features of DVB-T is the GuardInterval, which allows the receiver to make use of reflections,echoes, multipath interference, or for a SFN, signals receivedfrom additional transmitters which appear as a long echo. I am not an expert on this, but as I understand it, the maximumdistance between separate transmitters on the same frequencywhich send the same programmes is determined by the guardinterval. In countries where use is made of a Multiple-FrequencyNetwork (MFN) such as France for the most part, the smallestguard interval is used, allowing for a higher available bitratefrom the 8MHz channel bandwidth, with the drawback that thereare more frequencies in use, and it is likely that one canreceive the same programming two or three or more times in onelocation between different transmitters. In contrast, in Germany (see the de-BW list which I posted tothis mailing list some weeks or months ago), the same frequencyis in use at several widely-spaced transmitters, but not so farapart 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 overallbitrate is available on a particular 8MHz channel. Hinted at in the de-BW list is that in Switzerland use is alsomade of several SFNs, consisting there of some higher-powertransmitters on a particular frequency, supplemented by manylower-power transmitters on the order of kilowatts, due tothe terrain making it difficult to cover the many valleys thatthe high-power transmitter fails to reach. The large numberof filler transmitters makes it impractical to list them allwith the redundant info in the way that I did in de-BW, thougha list can be downloaded in case specific information is neededto properly site a receiving antenna. With analogue broadcasting, this SFN use was not possible, asmore than one transmitter on the same frequency results inthe familiar interference that could be seen where multiplelow-power filler transmitters were received. For readers in ATSC-land, this can be a difficult concept tograsp, as for the most part, all stations are independent ofeach other and use a single high-power transmitting site, soas I understand from reading gripes on Slashdot (which is theclosest I care to come to understanding details of ATSC), thereis no provision made for handling multiple transmitters, and asa result, multipath interference or other echo sources, andreception is nowhere near as robust as the case I've experiencedwhere a virtually unwatchable analogue frequency is turned intoa clear DVB-T signal, and a literally unwatchable frequency isturned into mostly-clear DVB-T. That is, for US-types, thereis no concept of a national broadcaster (with, say, vaguetuning info, like, `97 to 99 FM' as opposed to a specificfrequency, `88.3 on your FM dial'). But I digress... Anyway, a guard interval of 1/32 would be used by a singletransmitter, or perhaps two closeby transmitters on the samefrequency, whereas for a Single-Frequency Network (SFN), Iwould expect to see a different value, depending on the sizeof the coverage area, like 1/8 as in Paris, or 1/4 as usedfor the national and regional broadcasters in Germany. Thisis why I was somewhat confused by the conflict of seeing theuse of SFN to refer to Kiev, while seeing 1/32 given as aguard interval. But I am completely unfamiliar with theDVB-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 to634MHz 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 followingmessage) > 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 ontothe 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 satelliteDVB-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 thetuning 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 thisfrequency. Which seems strange, because `scan' appeared tobe able to list the services. However, this might be easier -- at least in my outdated`dvbstream' the default FFT transmission mode is 2k, whileit should be specified as 8k for Kiev, so you will need toadd `-tm 8' to your above command line. Try that and see if it works... The other parameters seem to be correct, at least as seenin 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 valuesat 714MHz for channels 51 | 714,0 | KΓTPK, 1+1, 24, Toниc, Kyльтypa, Enter-φильм, УP-1, УP-2/Πpoминь, УP-3/Kyльтypain place of `AUTO' and try that, maybe that will work. I think there are some tuners that require specific valuesand will not work with `AUTO', although there are many thatwill work... hope this is helpfulbarry bouwsmasome random 8-bit chars to make sure this gets tagged as utf-8...„…™ψöžא _______________________________________________linux-dvb users mailing listFor V4L/DVB development, please use instead linux-media@xxxxxxxxxxxxxxxxxxxxxxxx@linuxtv.orghttp://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
