Rs errors

[ross94]

Hi all, its that time of the year when the tree comes out when i set the Christmas tree near the window where we usually always put it. I noticed the tv went a bit funny for a few minutes coincidentally just after i put up the tree in the corner near where the virgin media intake equipment is.
I checked the diagnostics and this is what i found
what does the rs corrected and uncorrected mean? This is the highest of all 5 channels.
This is the results about an hour later and all the errors for each channel are back to zero,
Could it have been noise ingress temporarily? The tv has been fine since then and all errors remain at zero.
Any clarification would be great on this, what do the rs errors mean, also what should the snr be? The virgin media box i have is a v6.
I have heard the virgin media network is very sensitive to noise ingress which can affect other people in the same neighbourhood as well as your own property, i have seen a few posts where people have been cut off because of it. I hope i haven't caused an issue? Any advice from the experts on here would be appreciated thanks.

 

[rikaka]

make sure all the connections are tight. finger tight then a wee turn with your pliers or spanner if you have a 11mm

 

[Lucid]

RS stands for Reed Solomon. It's an error correction algorithm that Virgin Media use. The corrected and uncorrected lines refer to whether or not the algorithm was able to fix the errors that were detected.

The SNR (Signal to Noise Ratio) should be above 34. Yours are, so that's fine.

You got some pixellation because of two things. First was possibly disturbing the cable. Second was the presence of the transformer for the Christmas lights.

I've never really needed to go in to it, but the way that the compression works for MPEG- type transmissions such as digital TV is that there's a key frame followed by a number of images that simply carry the difference between themselves and the key frame. To keep the maths simple, let's pretend for a moment that there are 24 frames of video per second in your VM signal. Every second we send a Group of Pictures (GOP) comprising one key frame and 7 difference frames, then another GOP, then another. Three GOPs per second. Each GOP accounts for 1/3rd of a second. If the signal is affected by noise that wrecks one of the key frames, then that also affects the following 7 difference frames because the base on to which they paint their differences is missing.

Moving the cables (if that happened) can result in the centre core connection sliding in or out a tiny fraction against its contact inside the socket. It isn't damaging anything or coming disconnected completely; it's just rubbing metal on metal at a microscopic level. There's bound to be a little oxidation on the centre core and pins which is getting rubbed off. This is enough to cause some disturbance temporarily. It's a bit like rubbing your hand or some clothing over a microphone. Tightening the outer plug connection if loose enough to turn by hand won't hurt, but neither will it prevent the centre core moving if the cable is bent slightly.

The tree lights power supply is electrically noisy. It's what we call a switch-mode power supply. That means its chopping the rectified power signal to produce the voltage reduction, and in the process it's spitting out some radio frequency and electromechanical interference while it comes to temperature. Your Virgin box is picking this up.

You might have seen electrical interference of a similar nature in the past. People would get lines on their TV screen when on if a vacuum cleaner was used that didn't have a suppressor fitted to the motor. It would be the same when cars and motorbike had points and either didn't have a suppressor or it was going faulty. None of this should cause you a problem with the tech guys at Virgin Media, so don't worry.


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[ross94]

Thanks, i may well have disturbed a cable i mean there is quite a lot of cabling in that corner as its where the router is and there is also a splitter that connects to a white box on the wall which i am pretty sure is the incoming feed from outside, the Christmas lights have a big chunky transformer also. Your description makes a lot of sense and sums up exactly what has happened ,i'm glad there is nothing to worry about.
Thanks and have a happy Christmas.