[mythtvnz] Plummeting WAF with DVB-T artifacts

[Curtis Walker]

On 29 November 2013 10:52, Greg Brackley
<lists-mythtv-nz at lucidsolutions.co.nz> wrote:
> After running MythTV with DVB-S for many years I have upgraded to MythTV
> 0.27 and cut over to a DVB-T tuner. We are seeing a lot of video corruption
> in TV scenes with movement (on channels 1, 2 & 3). Typically a head or
> moving object will pixelate or get fuzzy edges.  This will happen every few
> minutes. The sound sometimes glitches as well.
>
> I'm getting signal from Sugarloaf in Christchurch. Are other people getting
> a good picture?  I have spoken to a couple of people with different tuner
> hardware and a different version of MythTV and they are reporting similar
> issues.  Is it a MythTV thing?  I don't have a reliable non-mythtv tuner to
> compare against. In theory the MythTV backend is just copying the transport
> stream to disk, so I am trying to figure out where things are going wrong.
>
> I've tried to re-mediate and check off possible problems:
>
> I've changed the antenna to a UHF only antenna (02MM-MDU36) - this is higher
> gain that required
> The cabling is all properly crimped and sealed
> I do have some trees that aren't feasible to trim in the line of sight
> I am using a HDHomerun
>
> with the latest firmware (20130328)
> reasonable signal strength, 100% SNR and symbol error quality
>
> my backend recordings are on a NFS drive that can write at greater than 40M
> bytes/sec
> the network switch isn't reporting any error frames
>
> GbE switch
> Intel NICs
>
> on the frond end, rewinding over the glitch doesn't overcome the issue
> copying the files to a windows machine and watching with VLC doesn't fix the
> issue
>
> VLC seems to pause through the errors rather than showing pixellation
>
> I've tried leaving a ping running against the hdhomerun
> the backend is:
>
> a CentOS v6.4 virtual
> MythTV 0.27
> NFS for the video store
>
> I don't have a backout plan as the old machine has ECC memory errors, very
> old disks and the DVB-S tuner is a 5volt only PCI card
>
> Any ideas please?
>
> Greg.
>
> --
>
> # hdhomerun_config ffffffff get /sys/version
> 20130328
>
> # hdhomerun_config ffffffff get /tuner0/debug
> tun: ch=t8qam64:594000000 lock=t8qam64:594000000 ss=93 snq=100 seq=100
> dbg=-417/-12288
> dev: bps=26344064 resync=0 overflow=0
> ts:  bps=26344064 ut=95 te=0 miss=0 crc=0
> flt: bps=2210880
> net: pps=210 err=0 stop=0
>
>
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>

 Do you have another way of checking the signal i.e. a
freeview-capable TV? If it's glitchy on a TV, the signal is probably
not good enough for a PC-based solution.

Can you check your setup under another OS e.g. Windows Media Centre?
If it's not pixellating there, then at least you know the hardware /
signal side *should* be usable in MythTV.

I had similar dilemmas (although the pixellation and sound glitches
were every 10-15 minutes) previously and tried everything - checked
antenna, wires etc. Tried an attenuator. Reformmated hard drives to
XFS. Pulled hair out. In the end the problem turned out to be that I
didn't have the correct firmware installed for my DVB-T card. This
*shouldn't* be a problem for the HD Homerun, but you never know.

Lastly, do the logs tell you anything?