> From: [email protected]
> To: [email protected]
> Date: Sat, 13 Feb 2010 15:54:23 -0500
> Subject: Re: [ivtv-users] hvr-1600, frame CRC mismatch - incomplete frame
>
> On Sat, 2010-02-13 at 14:32 -0500, Devin Heitmueller wrote:
> > On Sat, Feb 13, 2010 at 1:35 PM, Kyle Lil <[email protected]> wrote:
> > > 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 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.
> >
> > Kyle,
> >
> > Just to be clear, the BER/UNC counters count the number of errors
> > *only* between the tuner and demodulator. These are errors where the
> > Reed-Solomon error correction built into the signal could not
> > compensate (essentially errors in the analog signal transmission).
> > I'm pointing this out to make clear that those counters do not track
> > any *other* possible class of problem,
>
> Devin,
>
> Right. My statement about EMI was that signals inside the computer are
> affecting the IF signal on the card.
>
> (Sometime back on a list that I monitor, I recall someone with a disk
> controller right next to their TV capture card causing problems. Moving
> the TV card away from the disk controller card fixed the issue.)
>
> Since SNR wasn't really changing for Kyle, my guess was the errors come
> from strong "narrowband" and/or "burst" noise superimposed onto the IF
> from within his computer. Since the operation of the computer internals
> could easily behave differently between Windows and Linux, this seemed
> plausible to explain different results between Linux to Windows.
>
>
> The SNR reported for QAM is just a conversion from an averaged quantity
> being reported by the chip. I suppose the averaging interval could be
> hiding actual error bursts coming down the cable, so we never see SNR
> dip. However that would not explain why he didn't notice any video
> defects under Windows (assuming the Windows rendering app and linux
> rendering app handle errors in the same way).
>
>
>
> > such as packets being lost in
> > the cx18 driver, the application's failure to read the packets from
> > the driver fast enough (resulting in the packets being dropped by the
> > driver), or problems writing the MPEG frames to the hard disk, etc.
>
> My suggestion was more about disk activity causing EMI internal to the
> PC case. I had in mind perhaps a disk controller card next to the
> HVR-1600.
>
> Regards,
> Andy
>
> > Devin
>
>
>
> _______________________________________________
> ivtv-users mailing list
> [email protected]
> http://ivtvdriver.org/mailman/listinfo/ivtv-users
Thanks Devin and Andy. This is very informative. I tried moving the tuner card
to the PCI slot on the far end of the motherboard and leaving the video card (a
GeForce 210, I think I forgot to mention) as the only other card plugged in.
This however did not noticeably reduce the rate of errors.
Devin, you seem to be suggesting that the "glitches" I'm seeing watching TV
through mythtv are not necessarily the same as the unc/ber that azap is
reporting. That could also explain the difference between Linux and Windows
viewing. I should mention that I can play HD television in mythtv from a
firewire connection to my cable box without the glitches. But just to
double-check if the application is a problem, could you guys suggest another
application to view the video stream? I tried "mplayer -cache 8192
/dev/dvb/frontend0", but it does not play the video. I get the following
message:MPlayer UNKNOWN-4.4.1 (C) 2000-2009 MPlayer TeamPlaying
/dev/dvb/adapter0/frontend0.Cache fill: 0.00% (0 bytes) Exiting... (End of
file)
Also, is there a way to determine if the cx18 driver is dropping packets?
Best, Kyle
_________________________________________________________________
Hotmail: Trusted email with Microsoft’s powerful SPAM protection.
http://clk.atdmt.com/GBL/go/201469226/direct/01/_______________________________________________
ivtv-users mailing list
[email protected]
http://ivtvdriver.org/mailman/listinfo/ivtv-users
