> > This looks like EMI of some sort to me. (Either that or some > tracking > > loop in the digital tuner or demod losing lock - but then SNR would > > likely dip). > > > > EMI might be coming from inside the PC. Does your computer under > linux > > happen to write to disk every 30 seconds or so?
> The hard drive is being accessed pretty frequently (~1/second) when > watching tv with mythtv, much more often than the errors are > appearing. So, the hard drive cannot reliably produce the errors. > Interestingly, I think the errors seem to occur slightly more often > when watching tv with myth than when just monitoring the signal with > azap. Would azap catch all errors or does it just sparsely sample the > signal? The unc errors are accumulated in hardware counters in the CX24227 digital demodulator and then (unfortunately) cleared by the CX24227 hardware after an application like azap asks for the statistics to be read out. But if you know you only have one app reading the stats, and I'm pretty sure MythTV doesn't read them regularly, then you should be getting realistic reporting. BTW: the s5h1409 driver for the CX24227 really only reports uncorrectable block count and SNR. You can ignore the Signal and BER values as they are just duplicates of the other values. > The optical drive is not spinning up and the graphics card is fanless. > The only other significant EMI sources inside the computer that I can > think of are the case fan, cpu fan, and maybe the power supply. I can > play around with different ground configurations to see if that > helps. I would try moving the card to the slot farthest from where it is now or simply just away from other cards. The MXL5005s digital tuner is inside a little metal shield, but, IIRC the board traces over to the CX24227 and the CX24227 are not shielded. BTW I'm looking at the output of femon (since mythbackend has the adapter open) for my HVR-1600. With ATSC 8-VSB, I get an occasional error on a weak station, but not on the strong ones (except one or two lines after mythbackend changes the RF channel). That doesn't tell us too much about QAM demodulation though. Regards, Andy _______________________________________________ ivtv-users mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-users
