Incosistency between TV and DVB-T card

    Hi

    I use local cable provider which deliver non-standard DVB-T frequencies.

    I have Samsung TV, and from what I can see, it scans channels on MUXes with frequencies: 506,514,522,530,538,546,554,562,570,578,586,594,602,610,618,626,634,642,650,658,666. Technician said it starts with 506000, and jumps by 8000, modulation 256QAM, 6900 transmission speed. In TV everything works.

    I have also quad DVB-T card identified as Silicon Labs Si2168. w_scan finds such frequencies:

    # T[2] <freq> <bw> <fec_hi> <fec_lo> <mod> <tm> <guard> <hi> [plp_id] [# comment]

    #------------------------------------------------------------------------------

    T 730000000 8MHz 5/6 NONE QAM64 8k 1/16 NONE # Imperium

    T 738000000 8MHz 5/6 NONE QAM64 8k 1/16 NONE # Imperium Cofdm

    T 746000000 8MHz 5/6 NONE QAM64 8k 1/16 NONE # Imperium Cofdm

    T 754000000 8MHz 5/6 NONE QAM64 8k 1/16 NONE # Imperium

    T 786000000 8MHz 5/6 NONE QAM64 8k 1/16 NONE

    T 794000000 8MHz 5/6 NONE QAM64 8k 1/16 NONE # IMPERIUM

    T 802000000 8MHz 5/6 NONE QAM64 8k 1/4 NONE # Emitel

    T 818000000 8MHz 5/6 NONE QAM64 8k 1/8 NONE # IMPERIUM

    T 826000000 8MHz 5/6 NONE QAM64 8k 1/16 NONE

    (and these are not all, for example there's missing 810000000 frequency, I can add it manually and it later works

    Those frequencies also works, I can scan them with w_scan getting for example such a channel:

    HGTV HD;TVN:738000:B8C56D0G16M64T8Y0:T:27500:532=27:850=pol@3,851=org:0;6031:0:4315:0:0:0

    On the other side the same channel read from TV (using Samsung channel editor from http://www.samychan.com/) shows:

    At the end I have two different sets of channels: in TV and in computer tuner. Most channels are in both sources, but some of them are in TV only, and some in computer tuner only.

    I really don't understand, why they doesn't see the same frequencies.

    It looks like my provider emits on two sets of frequencies, and (at the same time) TV sees only one set, and computer card - second one.
    The other option is those frequencies are the same, but somehow re-mapped (but different QAMs suggest it's not true)


    I'd like have the same set of channels in both sources. Pls help me understand what's happening here.

    Hi,

    Did you try t2scan already?

    It is sometimes better...

    Regards Stefan

    Test-VDR1: HP rp5700 Fertigsystem, Core2Duo E6400, 2GB RAM, FF-SD C-2300, nvidia Slim-GT218 x1 | easyVDR 2.0 64Bit
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    VDR-User #1068
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    hmm..


    w_scan is outdated now - really. Also it's forks, called t2scan, w_scan2...

    SurfaceCleanerZ advice to use t2scan will not help either.



    At the end of the day, any 'channel scanner' relies on the *service information data* transmitted in the digital transmissions.

    And if that data is wrong, you will get wrong results. In your case, your local cable provider changes frequency of signal, but doesnt adapt the informations send in the digital transmissions. Most likely, any program without the internal details of the used tuner hardware will fail here, and hardware vendors have more possibilities.


    Also, the term 'frequency' is not that clear if using DVB-T/T2. There are transmitters, which simply repeat the signals on other frequencies, without adapting the it's contents to let receivers know about. In such case my tool w_scan will fail, but also any newer tool is likely to fail.


    I suggest to use 'dvbv5_scan' here, using the info you already collected, for each freq. separately. And: turn auto updates for transmissions off, no matter which program you're using later.

    I've build & used t2scan, but yes, it didn't do much. I'll attach output in spoiler. I can play with some parameters, like longer timeouts, which has helped w_scan find more channels (more then 40). I'm surprised frequency isn't stable term, but it clarify the inconsistency between TV and card. Now the question is how should I proceed? I've tried multiple software: NextPVR was unreliable and found only a few channels, TVHeadend found many channels but not all (and I didn't found possibility to manually add missing), so I went back to VDR which I'm using for 10(?) years, because it gives me most control. I was thinking I can somehow use my TV as a source of truth, but if it isn't reliable source, what can I do to correctly scan and find all channels?


    Edit: By frequency I mean frequency of MUX. If I would be able to gather all MUXes initial scan data correctly set, I think scanning would find all channels

    I forgot to add that I've tried dvbv5_scan, but it needs initial data, and even if I've used some DE/PL data, it didn't found any channel :(

    But I can repeat that process, if you give me an example


    Zitat von Marx2

    I have Samsung TV, and from what I can see, it scans channels on MUXes with frequencies: 506,514,522,530,538,546,554,562,570,578,586,594,602,610,618,626,634,642,650,658,666. Technician said it starts with 506000, and jumps by 8000, modulation 256QAM, 6900 transmission speed. In TV everything works.

    Another idea: 6900 transmission speed (I guess "symbol rate" is meant) sounds like a typical DVB-C symbol rate. Are you sure that your TV is really receiving DVB-T and not actually DVB-C? That could well explain these inconsistencies.

    Maybe you just want to create yourself an initial tuning file for dvbv5_scan like this:



    I added the first two frequencies that you listed (506 and 514) with the symbol_rate and modulation_parameter that you listed and DVBC. Just add all the other frequencies in the same way and give it a try.

    You did it! I've used those two only just to test and it automatically discovered all others and scanned them successfully. And now mystery is solved, as those channels are DVB-C channels. I had no idea that both standards are emitted at the same time on the same cable, but it explains everything. Thank you!

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