Pixelation when watching UK Freeview channels

[kitehigh]

Hello, I have been searching the web but so far haven't solved a problem which has plagued our HTPC experience!

Basically we get varying amounts of pixelation occuring when watching UK freeview channels (DVB-t). This gets worse as more tuners are in use.

With one tuner we may get a pixelation / glitch over a small section of the screen every 30 - 40 seconds.. not so bad but annoying.
With e.g. 3 tuners recording, 1 live TV we get severe glitches every 5-10 seconds, i.e. half the screen is pixelated. This is not useable.
Pixelation is present in recordings at the same places as in the live stream.

We have tried Next PVR, Argus TV and Mediaportal - picture quality in these is fine, so this is WMC specific, however these don't do what we want so really need to get to the bottom of the WMC problem.

Set-up:
- P8H61m-pro mobo with G620i processor, HD2000 integrated graphics
- OS on a 64GB SSD
- TBS-6284 quad dvb-t/t2 tuner
- Recorded TV to 300GB WD Blue 2.5"
- 2 * 2TB WD greens for media storage - not used for WMC.
- 2GB RAM
- All on standalone PC, not networking involved.

Things I have tried:
- Turn off CPU power saving (EPU, intel speedstep)
- Move tuner to other slots
- Fresh install(s)
- Monitor disk and CPU activity during pixelation events - no spikes etc
- Signal quality ok - normal TV fine, other programs fine.
- Make sure there is nothing else running in the background other than what is necessary for WMC.
- Change recorded TV to SSD - same pixelation.

Can anyone suggest any other things I can try?

[milli260876]

New cpu with more graphics oomph....
Up the shared graphics memory in bios.
Check for new graphics drivers.

[milli260876]

Is the pixilation better or worse on HD channels?

[kitehigh]

New cpu with more graphics oomph....
Up the shared graphics memory in bios.
Check for new graphics drivers.

Is the graphics card involved in recording when I am not watching anything? I have the same problems on recordings e.g. overnight when the pc is otherwise not being used.

Is the pixilation better or worse on HD channels?

Same for HD and SD..

[mark1234]

New cpu with more graphics oomph....
Up the shared graphics memory in bios.
Check for new graphics drivers.

Is the graphics card involved in recording when I am not watching anything? I have the same problems on recordings e.g. overnight when the PC is otherwise not being used.

The graphics card is only used for playback, it plays no part in the recording. I think where milli was going is that, providing you do have good signal, the recording should be fine as the tuner will simply dump the digital stream that it receives, it's not really interpreted at all until playback. So, the kind of issues you're seeing would most likely be GPU related.

But... if you're getting the same on SD and HD then I'm going to say that the GPU shouldn't be the issue as the workload with SD is tiny compared with HD.

I know you originally said that you have good signal, but can you check the signal strengths? I've seen first hand my TV happily show every channel, yet connect the same wire to 7MC and it all falls apart. You might also be receiving signals from multiple transmitters, and I've seen 7MC decide to use a lower power one over the one you want it to use.

Do you have another PC that you can copy the .wtv file to and see if the issue is in the recording or in the playback?

[kitehigh]

Ok, that gives me a couple more things to try..

I'll copy a recording over to another PC and see if the pixelation is the same.

Also I have a GT610 spare - hadn't tried this as I didn't think gpu had anything to do with the recordings but will put it in and see if there's any difference.

[holidayboy]

Definitely worth checking in tasks\settings\tv\guide\edit channels to make sure the correct frequencies are being used for each channel.



As Mark says, MC is fussy when it comes to signal strength. It is possible to have a signal that is too strong for reliable reception, obviously a weak signal will also cause issues.

[kitehigh]

Yes I have been through the process of splitting out the 3 sets of frequencies it picks up and making sure the correct one is selected so that shouldn't be a problem.

I wish there was a way to restrict the frequencies scanned to ones I know are correct..

[kitehigh]

New cpu with more graphics oomph....
I know you originally said that you have good signal, but can you check the signal strengths? I've seen first hand my TV happily show every channel, yet connect the same wire to 7MC and it all falls apart. You might also be receiving signals from multiple transmitters, and I've seen 7MC decide to use a lower power one over the one you want it to use.

What's the best way to check signal strengths as I do not believe what is reported in WMC - is there a standalone program I could use?

[Pixelz]

From inside Media Centre, have you tried pressing 4 1 1 followed by 'i' on your remote?

Not sure if this gives signal strength, but I seem to remember a page showing error rates.
I need to check when I get home.

[milli260876]

There is a dedicated signal strength program cant for life of me remember tho..
I moved onto freesat some time ago.
I'll have a think!!!

[CyberSimian]

There is a dedicated signal strength program cant for life of me remember tho..

Are you thinking of "ScanChannelsBDA_UK.exe"?

This program was eventually open-sourced, and others made "enhancements" to it, so there are now numerous different versions on the internet, with inconsistent version numbers. The original did not handle DVB-T2, but one of the later versions might. I have three versions in my program store (2.6.3, 2.7.0, and 2.8.1, although I am not sure that those version numbers are meaningful).

-- from CyberSimian in the UK

[CyberSimian]

We have tried Next PVR, Argus TV and Mediaportal - picture quality in these is fine, so this is WMC specific

This is an intriguing detail. I do not know anything about Next PVR or Argus TV, but what I do know about MediaPortal is that it uses only one tuner to record multiple channels from the same MUX. In contrast, WMC uses multiple tuners to record multiple channels, i.e.:

MediaPortal: one tuner per MUX
Media Center: one tuner per channel

So if your test of recording multiple channels involved channels from the same MUX, MediaPortal would use only one tuner, but WMC would use multiple tuners. Could this explain the difference? I don't know.

-- from CyberSimian in the UK

[milli260876]

There is a dedicated signal strength program cant for life of me remember tho..

Are you thinking of "ScanChannelsBDA_UK.exe"?
-- from CyberSimian in the UK

Yes!

[milli260876]

If you rewind a program does pixellation occur in the same place??

[kitehigh]

Yes the pixeallation is in the same place if I rewind or watch a recording back. So I would be surprised if ti was a gpu issue.

[tony_park]

Not sure if this helps, but I use 2xTBS DVBS2 dual tuners, and if I have the power settings set so that the minimum processor state is at 5%, using balanced settings, I get pixellation. However if I change the minimum up to about 10%, the pixellation doesn't happen any more, on newly created recordings. It has no impact on previously recorded programs.

I've never had this problem before, when I was using hauppauge tuners.

[kitehigh]

I know you originally said that you have good signal, but can you check the signal strengths? I've seen first hand my TV happily show every channel, yet connect the same wire to 7MC and it all falls apart. You might also be receiving signals from multiple transmitters, and I've seen 7MC decide to use a lower power one over the one you want it to use.

There is a dedicated signal strength program cant for life of me remember tho..

Are you thinking of "ScanChannelsBDA_UK.exe"?
-- from CyberSimian in the UK

Checked signals - all tuners around 90 % strength and 89% quality. I recently had a new aerial fitted with a single cable running directly to the TBS-6284 - no splits, joins or other devices in between. I have an unobstructed line of sight to the transmitter according to the information on ukfree.tv.

[kitehigh]

Not sure if this helps, but I use 2xTBS DVBS2 dual tuners, and if I have the power settings set so that the minimum processor state is at 5%, using balanced settings, I get pixellation. However if I change the minimum up to about 10%, the pixellation doesn't happen any more, on newly created recordings. It has no impact on previously recorded programs.

I've never had this problem before, when I was using hauppauge tuners.

I believe this setting relates to Intel Speedstep which I have disabled in the BIOS. I'll give it a go anyway though!

[kitehigh]

We have tried Next PVR, Argus TV and Mediaportal - picture quality in these is fine, so this is WMC specific

This is an intriguing detail. I do not know anything about Next PVR or Argus TV, but what I do know about MediaPortal is that it uses only one tuner to record multiple channels from the same MUX. In contrast, WMC uses multiple tuners to record multiple channels, i.e.:

MediaPortal: one tuner per MUX
Media Center: one tuner per channel

So if your test of recording multiple channels involved channels from the same MUX, MediaPortal would use only one tuner, but WMC would use multiple tuners. Could this explain the difference? I don't know.

-- from CyberSimian in the UK

Ok, so I tried recording 4 shows in NextPVR - making sure each was on a different MUX - and guess what: same pixelation problem as in WMC...

So, it IS something upstream of WMC. To confirm I tried playing back a current recording and starting / stopping recordings on other muxes - the more simultaneous recordings the worse the pixelation becomes. This occurs on SD and HD but HD was worse on my testing this morning.

I have played back the files via VLC and the pixelation occurs at the same place (i.e. its the same frame-by-frame) so I don't think this is gpu/playback related - the recordings are pixelated before playback.

Before doing the above I also:
- Updated the BIOS
- Checked ASUS EPU power saving and Intel speedstep were disabled
- Checked Processor minimum power setting was 100%

During the recordings I watched CPU and HDD activity - again no spikes. Also tried changing recording folder to another HDD and an SSD - no difference.