[mythtvnz] Plummeting WAF with DVB-T artifacts

[Greg Brackley]

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
      o with the latest firmware (20130328)
      o 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
      o GbE switch
      o 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
      o VLC seems to pause through the errors rather than showing
        pixellation
  * I've tried leaving a ping running against the hdhomerun
  * the backend is:
      o a CentOS v6.4 virtual
      o MythTV 0.27
      o 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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