Looking for ideas to investigate random, infrequent pixelation during recording

[ukmark62]

Hi,

I'm using the latest version of NPVR (4.2.2) - I have also tried some older versions also with same results. This has been occurring ever since I started with NPVR about a year ago, and has also happened with other recording software such as media center, sichbopvr etc. I stick with NPVR because I like it the most.

The issue I'm trying to track down is an infrequent, random pixelation during recording. It might be that I get several perfect recordings, but then occasionally, I'll get maybe 1 or 2 glitches (each lasting less than 1 second) during a recording. These are all Freeview HD recordings and can happen on any channel at any time. For example, I recorded one programme yesterday and there were 2 glitches - yet today I recorded 6 concurrent programmes from the same mux with no issues at all.

I emphasize that these occur infrequently and as such makes it difficult for me to track down the cause and if anything can be done about it. I have checked through all the logs from NPVR and see nothing logged at the time the glitches occur. I only see start and end times logged.

PC is Windows 10 with 16GB RAM, 256GB internal SSD (this is where Windows and all programs are installed), a 2TB internal HDD (this is where the recordings are stored). PC is HP Intel Core i5-7200u with Intel HD 620 graphics card. All drivers are up to date. Windows version is 1803. If I use 'Ctrl + I' when viewing live TV the signal quality is always 85 to 90 range and signal strength is always 50 to 55 range - this is using Hauppauge WinTV-dualHD tuner - model # 01590. (I have 3 different tuners and each tuner exhibits this random recording problem. The other tuners are single tuner MyGica T230C and a generic Ebay single tuner that uses Astrometa drivers and these both appear to have 'hard coded' signal strength and quality readings).

The aerial coax cable comes directly from the roof aerial into the USB tuner and then into the USB port on the PC - this is in the upstairs bedroom. TV reception downstairs from the same aerial (different coax cable) has always been 100% reliable. I have no splitters etc.

The reason I'm posting is that I'm looking for any suggestions to identify and if possible fix the problem.

We have always had a good signal where we live and as I said, TV reception is always perfect (unless we have some very extreme weather). I'm going to give an aerial variable db booster a go (for the PC USB tuner only) and try increasing the db to see if this helps. Are there any other suggestions?

Thanks for reading!

[sub]

It is almost certainly reception issues.

If you've normally got pretty good reception, you may find it atmospheric - something like strong winds or rain causing your antenna (or trees your signal goes through) to wobble in the wind. Particularly good weather can also cause problems, with distant radio signals travelling further in high pressure situations potentially interfering with otherwise good local signals.

Whether you can do anything about this, I don't know.

[Bobins]

If the glitch is appearing in the actual recording and you say it happens when using different tuners, my suspicion would be signal related. Signal strength is one thing, signal quality is in some respects more important.
If you have a single aerial split to two tuners (TV & PC) without some sort of amplification, there's a much higher chance of signal problems. It's always better to split the signal through a small distribution amplifier as close to the aerial as possible.
TV's are also more tolerant of signal "blips" than PC based recorders so you may not notice a signal problem on a TV till it becomes really bad.
These transient things are always difficult to track down though except through a process of progressive elimination.

[ukmark62]

It is almost certainly reception issues.

If you've normally got pretty good reception, you may find it atmospheric - something like strong winds or rain causing your antenna (or trees your signal goes through) to wobble in the wind. Particularly good weather can also cause problems, with distant radio signals travelling further in high pressure situations potentially interfering with otherwise good local signals.

Whether you can do anything about this, I don't know.

Thanks sub and Bobins, my gut feeling is the same - I'm aware that TVs are better at handling small blips than PC USB tuners - but was hoping I'd missed something obvious. I'll still go ahead and test the aerial booster - I have read on the net that it has helped some people. Do you know what are the recommended quality/strength readings for freeview hd in the uk?

Cheers.

[Bobins]

Regrettably there is no consistency between different tuner softwares on how they report signal strength/quality. The simple answer is if it's a percentage, quality as close to 100% as you can get is best. As Sub said, atmospherics/environment will often cause dips below what a tuner reports at any point in time so you want as big a margin as possible above the problem threshold.

[Stanno]

I don't have any suggestions but I can sympathise. I record everything twice (She Who Must Be Obeyed would kill me if one of her series failed to record) and as well as an Intel NUC recording with NPVR (our main machine with a USB tuner) I also record on a Humax HDR2000. Both machines are fed direct from a powered splitter. I often get pixellation on the NUC but if I look at the same recording on the Humax it's always perfect so I put this down to the USB tuner. There is no way I would switch to using the Humax for my main system as NPVR gives me so much flexibility to "tweak" things so I just live with the occasional imperfections.
Stanno

[ukmark62]

Would it be fair to say that USB tuners often need a boost to signal strength/quality in comparison to TVs?

In my bedroom, I have a TV and changed the aerial from the roof coax cable (so that I could dedicate that cable to the USB tuner), to one of the new cheap chinese ebay small flat rectangular shape plastic aerials - cost around £4. I bought one on a whim and had very low expectations. However, I can get ALL channels on the TV with it in perfect quality - no dropouts. Using the built-in Panasonic TV signal condition tester, it shows quality between 80-100% (more often at 100%) and strength between 60-70% for this ebay aerial.

However, if I plug the ebay aerial into the Hauppauge WinTV dualHD tuner, I get a scrambled mess. That's why I'm hoping the aerial booster (SLX model 27828HSR) will boost the signal strength/quality fed directly from the roof aerial into the USB tuner to make it as good as the TV. The SLX model has a reported noise gain of less than 3dB, with variable boost of up to 20dB.

It's frustrating as the picture on the USB tuner is fantastic - just get these occasional, rare, very short recording glitches.

I'll update this thread with my findings.

[Lao Pan]

Would it be fair to say that USB tuners often need a boost to signal strength/quality in comparison to TVs?

However, if I plug the ebay aerial into the Hauppauge WinTV dualHD tuner, I get a scrambled mess. That's why I'm hoping the aerial booster (SLX model 27828HSR) will boost the signal strength/quality fed directly from the roof aerial into the USB tuner to make it as good as the TV. The SLX model has a reported noise gain of less than 3dB, with variable boost of up to 20dB.

It's frustrating as the picture on the USB tuner is fantastic - just get these occasional, rare, very short recording glitches.

I'll update this thread with my findings.

Just a few observations

Several USB Tuners actually need more power than some Motherboards can supply - resulting in picture breakup - I fitted new aerial had it aligned etc, when all it needed was a powered hub.

Sometimes my HTPC starts to glitch, gradually getting worse - only thing that will fix it is a cold reboot (anyone got a batch file that pulls out the plug? ) Also the monthly .net rollup update will often cause the same problem.

In the UK there is a huge amount of Infrastructure Upgrade going on so that they can steal the 700Mhz band and sell it for 4G use. A lot of Transmitters have been on low power for weeks at a time while the work is carried out, there is also more chance of Co-channel interference while the frequencies are moved about.

[Tacoma]

Hauppauge includes a signal meter with the WinTV software. I live in a fringe area. I use the signal meter to tune my antenna to get the best signal. It works well with NextPVR. Load NextPVR windowed then the signal meter. As you change channels the meter will show the signal strength. This should help determine which stations are weak and in danger of breaking up.

[ukmark62]

Hauppauge includes a signal meter with the WinTV software. I live in a fringe area. I use the signal meter to tune my antenna to get the best signal. It works well with NextPVR. Load NextPVR windowed then the signal meter. As you change channels the meter will show the signal strength. This should help determine which stations are weak and in danger of breaking up.

The Hauppauge tuner I have has 2 built-in LEDs that are either red, yellow or green (it uses Hauppauge's own SNR program but is loaded directly on the device). The tuner always shows green. The glitches I have are very short in duration and happen rarely - I would estimate that in terms of reliability, I would be getting over 99.9% rock solid data. Normally, it would not bother me too much, it's just that I only record TV that I'm going to keep for the long-term - so that's why I want it to be glitch-free. Probably asking too much for a USB tuner - but I'm waiting for the booster to try that.

I do have a Humax PVR that works flawlessly - but I find the convenience of NextPVR on the PC hard to beat. I also re-encode the .ts recording to x265 (reduces file size dramatically without any noticeable drop in quality). I may have to revert back to the Humax and copy the recordings over to my PC to re-encode them but I want to avoid that if possible.

Cheers.