[mythtv-users] DVB-T tzap versus mythtv 0.19

[Doug Scoular]

Hi All,

> 'm seeing the same thing on Myth 19. When starting
> LiveTV it takes about 6-10 secs to start, which is a
> problem, but far worse is that that is that the card
> (Nova-T DVB-T) fails to tune about 50% of the time.
> Myth 18 worked perfectly.
>
> If I tzap it, the card tunes in first time, every
> time.
>
> Quite often LiveTV will also lock up mythfrontend. 

    I wonder how many 0.19 users with DVB cards are
    having tuning problems ? All my colleagues with 0.19
    and DVB-T cards are experiencing tuning issues.

    That being said everyone I know is based in Australia,
    so maybe its specific to Australian TV... I'm not sure.

    Is anyone outwith Australia having DVB-T tuning problems ?

    I'm not too concerned with the 6-10 seconds to change
    channels... it's the lack of actual tuning reliability and
    the frequency of frontend death/lockup thats causing me
    the most pain.

    Under 0.18.1 if I got LOCK I got a picture... now I get
    very variable Partial Lock... Full Lock... L... LA... LAM
    under 0.19. Tuning under 0.18.1 was rock solid on my
    setup... no antenna or card setup has changed at all. Frontend
    crashes were very rare.

    I'm hoping to go through the source this weekend to see
    if I can figure out what the problem is. I also posted on
    the LinuxTV DVB list and they said that the values
    returned from a DVB driver for signal should be ignored
    as the scale is not linear and varies from driver to driver.
    BER and UNC being a better measure. As per this from Patrick
    Boettcher:

> I have to admit, the way the signal strength is currently calculated 
> is wrong and stupid.
>
> Problem is, to have really correct RF power calculation we need more 
> information on the board and floating point operations in the kernel.
>
> OTOH, I repeat myself here, I don't see the reason, why MythTV is 
> taking the Signal strength into account and drops a receiver from the 
> list, when it is zero. In DVB we have much easier values to see if the 
> stream is maybe garbled or not and this is the UNC and BER.
>
> Maybe it is worth for mythtv to add an option to disable the 
> consideration of signal strength and SNR when using it with DVB.
>
> regards,
> Patrick. 

    Now, I don't know if MythTV uses UNC and BER and ignores SNR
    and Signal when tuning... but that's what I hope to figure out over the
    weekend. Also, if they are erroneous why display them ?

    Any help much appreciated... I love my MythTV!

    Cheers,

    Doug