QAM record problem with logs -- HELP please (4 Viewers)

[mm1352000]

In sum, it doesn't look like amplifying the input signal would help the situation. Do you agree?

I'm not completely certain which pictures correspond with each testing scenario. In any case I feel like I'm getting out of my depth - I'm an electronics and computer systems engineer but I leaned towards software half way through my degree. In other words, I know enough about this stuff to get me out of trouble in a pinch (or into a worse mess in some cases... ) but not enough to deal with issues like this over the internet...

At this point what can we say? I think you have a clear and consistent way to reproduce the problem - don't underestimate the importance of that. The problem seems to be frequency-specific and probably relates to the way the tuner demodulator locks on to the signal. Something about the electrical environment when one tuner is already operating causes the second tuner not to be able to lock properly in some cases. It is possibly not constructive to try to diagnose the problem any further than what you've done as at this point as I'm reasonably certain that this is an issue "caused" by characteristics defined in the tuner driver... and we can't fix the tuner driver.

So what *can* we do? Well, I think you have a few options.

Firstly you can try older and/or newer drivers. The newest drivers are usually recommended, however in cases like this sometimes an older driver is worth trying. You never know - older drivers might not give the same problem... but they might have other issues that aren't present in newer drivers. Worth a shot either way.

Secondly, you could get a professional in to look at the problem. Your ability to alter the signal power is ultimately limited, and testing is time consuming. You can only connect/disconnect so many connections, and 3dB either way may not be enough to make a difference (remember that my amplifier is 15dB). A professional should be able to do real time changes with a variable amplifier/attenuator. That would enable you to quickly find out if signal level adjustments are able to solve the problem or not. A more complex solution with band attenuating filters may be possible, however you'd only really know if you got someone with the right equipment and knowledge to have a look. That may be somewhat costly - it would be completely up to you as to whether you think it is worth the investment.

Another option would simply be to buy another splitter and tuner. One would hope that you wouldn't experience the same issues across cards, and if you were concerned about that you could always get a different brand/model. Of course there are no guarantees whatsoever...

Finally, if different drivers don't resolve the problem and you can't justify the cost of getting a professional in or buying a second card then maybe you have to live with it. You know about the issue and what causes it so theoretically you can consciously avoid it when you plan your recording schedules. Annoying? Perhaps, but one has to be realistic...

Any thoughts?

 

[cewillis]

I'm not completely certain which pictures correspond with each testing scenario

The left picture is for a problem channel (KOLD - 103.25) recording started first, and a good channel (KVOA - 139.25) started next. Both recordings are good in that case, as established before.

The right picture is for starting a recording, and then trying to record a problem channel. The second recording is poor in that case, and the monitor shows the second channel getting unrecoverable errors.

I agree with your assessment of the situation as of now. It's inconvenient but 'manageable' to a large degree.
Not sure what approach to take next, if any.

I notice something else: 103.25 Mhz is actually in the broadcast FM frequency band of 88 to 108 MHz. Don't know if that means anything, but there's nothing to be done about it anyway -- I can't make the cable company change the frequency.

Maybe Hauppauge could provide some useful info -- like 'we don't guarantee operation at that frequency'. I may have to install their WinTV software to get any help from them. If that software has the same problem, it would be more proof that the 2nd tuner can't tune at 103.25 while the first tuner is active. (I think we've established that!) But what if WinTV does not have the problem??

There's no chance that changing the hybrid tuner order in TVsetup would make a difference -- is there?

I think you've gone way beyond anything one could expect. Thank you very much.
I'll let you know if I stumble upon a 'solution'.

 

[Owlsroost]

Just a thought - a while ago I had a strange reception problem with one of my UHF DVB-T tuners - I could not get good reception on one RF channel (out of 6), but other tuners fed from the same antenna (via a splitter) worked OK.

I eventually found that if I put a bandpass filter (or an attenuator) immediately before the tuner everything was fine....

My theory (wearing my hardware engineer's hat) was that I was having electrical reflection problems in the cable feeding the tuner input, which was causing a dip in the frequency response at the problem frequency, and putting in the filter/attenuator had the effect of isolating (to some degree) the tuner input from the cable.

I'm not suggesting that this might be your problem, but since simple bandpass filters or attenuators aren't very expensive it might just be worth a try.

Tony

 

[mm1352000]

There's no chance that changing the hybrid tuner order in TVsetup would make a difference -- is there?

No, I'm afraid not...

I think you've gone way beyond anything one could expect. Thank you very much.
I'll let you know if I stumble upon a 'solution'.

You're most welcome, and please do give us an update if you find a solution. Although this doesn't appear to be an MP problem, I am still interested.

 

[cewillis]

I eventually found that if I put a bandpass filter (or an attenuator) immediately before the tuner everything was fine....

My theory (wearing my hardware engineer's hat) was that I was having electrical reflection problems in the cable

Thanks for the suggestion.
I'm with you on the bandpass filter, and the potential for noise of some sort. As mentioned above, my problem definately seemed to get worse when I removed a splitter that also claims to be a bandpass (with rolloff frequencies a very long way from the signal frequency).
But I don't get the attenuator. Wouldn't an attenuator reduce both the signal and the noise -- well, maybe that could work in the case of a strong signal. (but I'm not going to say how long it's been since electronics classes in college)

Can you tell me the bandpass parameters that you used?

 

[mm1352000]

But I don't get the attenuator. Wouldn't an attenuator reduce both the signal and the noise -- well, maybe that could work in the case of a strong signal.

Yes exactly - signals that are too strong (to the point of distortion) can be just as bad as signals that are too weak...

 

[cewillis]

Finally heard from Hauppauge. As expected, they want me to install WinTV to see if the exists with that software.
Will installing WinTV cause any problems with MP?

 

[mm1352000]

Hi cewillis

I'm not sure. Some people have had problems with it preventing TV Server from using tuners; other people don't have problems at all. Hauppauge asked me to install WinTV 7 to help troubleshooting a problem with one of my satellite tuners and it doesn't seem to cause any problems. Personally I'd just go ahead and do it...

mm

 

[cewillis]

Update

For easy reference, here's the problem:

I get 4 useful QAM channels, plus 2 others that are intermittent (and NOT tuned by any of my TVs), plus 2 or 3 others that I never look at.
The 4 are named KVOAHD, KGUNHD, KMSBHD, and KOLDHD. The latter two changed frequency recently)

Here is the test sequence that goes with the logs.
1. stop MP and TV
2. delete all logs
3. start MP (and TV)
4. use Scheduled -> New to start a recording on analog channel 3
5. use Scheduled -> New to start a recording on KVOAHD
6. verify recording playback and normal MP operation -- both good
7. stop recordings.
8. repeat 4 - 7 except use KGUNHD -- all good
9. repeat 4 - 7 except use KMSBHD -- recording is heavily pixelated, torn, distorted; audio intermittent and out of sync; MP operating v-e-r-y s-l-o-w
10. stopped MP, TV missing per Task Manager, do not delete logs, restart MP
11. repeat 4-7 except use KOLDHD -- recording is heavily pixelated, torn, distorted; audio intermittent and out of sync; MP operating v-e-r-y s-l-o-w, eventually 'Connection to TVserver lost'
12. stopped MP, TV missing per Task Manager, do not delete logs, restart MP
13. start recording on KMSBHD only -- all good
14. stop recording
15. start recording on KOLDHD only -- all good
16. stop recording
17. compress and send logs

I've tried several things to try to solve this problem, with no completely successful result.

1) an inline cable amplifier. Absolutely the wrong direction -- destroyed all reception on the HTPC.
2) a high pass filter that blocks frequencies below 54 MHz. No noticeable help, but probably can't hurt.
3) a few attenuators, 3bd, 6db, 8db. The 3db seems to help some, at least sometimes. I have successfully made some recordings that used to routinely fail; eq, start an analog (or KVOAHD) recording , followed by a KOLDHD recoding. Sometimes, I don't see anything at all wrong with the KOLDHD recording, sometimes just a few distortions. No complete failures yet with these channels.
However, the same sequence but with KMSBHD still has significant distortion, and an occasional failure (TVserver crash).
A 6db attenuator did not improve anything, and 8bd made it worse - although individual recordings (and viewings) still work.

As mentioned before, the recently changed frequencies of KOLDHD and KMSBHD (103.25Mhz) are in the FM broadcast range of 88-108Mhz. I don't know what the really means, but resumably, there's no FM on the cable(?), and I can't put a Faraday cage around the HTPC.
So it looks to me like this Hauppauge 'dual' 2250 tuner just does not work very well at this cable frequency; ie, one tuner operating at any frequency causes a problem with the other tuner at 103.25.
And it appears the only way 'around it' is the avoid the situation.

 

[Da_JoJo]

i have experienced this to and it only happens on HD channels. whipe all channels and scan again. this is probably also codec/cam-prog related. the hauppauge can tune just about anything, so that cant be the problem. i am playing wii games on the analog input of my hauppauge hvr-1300 in mediaportal with about 0.2 secs lag lol.
the thing is related to the decoding of the ts-stream. it is either the ts-writer/reader cannot cope with the speed of the multiple stream channels or it is the decoding part . since mediaportal worked fine before it must be cam related or mdplugin related or driver related. i keep it at qam decoding related issue. might be virtual tuner that is buggin.
what happens is it looses tuning and therefor decoding goes wild. i measured my signal and quality of it with prof gear and it is working fine.The minimum 50% signal / 50% quality should give one a crisp clear HD television image.