Hi all.

I've looked through all the other posts but not found a mention of this issue with the DHD 4000. So please accept my appologies if this has been done to death.

On a number of freeview channels when playing back a recording we get a large number of 'drop outs' I presume these are to do with the reception of the channel.

The annoying thing about these is that the DHD 4000 appears to drop both the sound and picture rather than just pausing the picture and continuing with the sound. It makes it almost impossible to watch the recording.

Is there a setting or a hack or a software update that resolves this issue? I'm on 2.3.9 version.

Any help would be greatly appreciated.

The trouble is that if there is sufficient loss of data to cause a dropout (so that error correction can no longer cope), the chances are that it will affect sound and vision fairly equally. No amount of software updates can put back data which is totally lost.

The problem is never apparant when watching the programs on these channels live though. We occasionally get glitches and pixelation in the picture but the sound is always fine. It's not that the 4000 box never has the sound it's just that it doesn;t seem to store it when recording - preferring to cut that (fraction of a second) section of the program out rather than pixelating the picture and continuing correctly with the sound.

The issue is this
- watching the channel say for example E4 on the DHD 4000 live it's fine no sound drop outs at all. Occasional pixelation - which is no particluar issue.
- watching a recording from the same channel gives significant drop outs of sound so that you're missing in parts of the playback about 50% of a conversation. Some recordings from the channel this will be the case for the whole of the recording - some recordings it will only be the case for a 5 minute period.

Disruption to the picture I can handle but when sound gets disrupted it really screws it up.

Thanks for the reply by the way.

Its sounds like you have some reception problems in general.

Have you thought about [a] an ariel upgrade, [b] get a booster or [c] change you coax routing.

You can try [c] first as it costs you nothing other than look at the DVD, VHS or other machines you have and maybe try routing the coax from the aerial into one of them 1st before routing it to the DHD4000, you may find it cleans or boosts the signal enough to keep the DHD4000 happy. [b] is cheap (£10-£20) and [a] will costs you a little (£60-£100) if you do not do DIY.

pzboyz

Thanks for the suggestion. I'll certainly give C a try. I thought going through another piece of kit first wouldn't particularly help.

We did get a new 'digital' ariel and a signal booster when we bought the DHD 4000 it looks like a beefy thing and the signal strength showing int the technical section is never below 10 for one mux and 8 for the other. I'm assuming that the affected channels (five and E4) are on the lower strength mux and don't get a great deal of bandwidth on that mux.

Can I take it from the replies that and drop in signal strength will cause this effect with the 4000 box and there's not a lot you can do about the sound issue?

I would have thought it would be easier for the box to record the signal it receives rather than purposely dropping the sound part to keep the video in synch??

Is it both the Signal Strength and Quality that are high, have low strength is not good, but low quality is a big problem.

Why did you get the booster with you digital aerial? Is this a fixed external aerial or an internal portable one?

There is such a thing as 'too much boost' too ... can you turn off the booster?

Is you home in the shadow of large buildings or large trees?

pzboyz

When we decided to buy a freeview receiver we got an ariel company round to look at the signal strength. They suggested that a booster was necessary (plus a new ariel) all told about £250.

I've looked at the strength using the DHD 4000 techinal area and it's significantly weaker without the booster on. We actually live quite high up with no large buildings around in a city (Nottingham) so I'm quite suprised that we have an issue with signal strength but this issue does only occur on certain channels. BBC are always fine. I'll see what the quality rating is tonight when I get home.

Thanks again

As pzboyz said, the quality is more important that the strength. Mine has strength 6 and a quality of 8, occasionally 9 for the BBC and I’ve (touch wood) never had this problem in the three and a half years I’ve had it. Perhaps you could post your quality levels this evening.

I’m somewhat puzzled as to why it appears to be worse on playback, since in theory what you see live is what gets recorded.

As a matter of interest how is your video error handling configured? Whilst in the technical section, press 1004 to enter the engineers menu which gives you engineering information. Then select startup, the third entry is Video error. You can toggle between freeze frame and macroblocking mine is set to freeze frame. I’m not sure of the exact difference between the two, other than there must be two ways of handling video errors.

Sorry I cannot be more of a help.

--John

A continuous signal strength of 10 is worrying. This could be overloading the tuner occasionally, creating the dropouts you experience.

Do you get any breakup when monitoring the tuner showing 10 in the technical page? (Use up/down arrows to select between tuners).

If all else fails on improving signal level, then try taking off the lid and re-seating the data and supply leads to the hard drive. The difference in quality between live and recorded programmes indicates that it might be other than signal level that's the problem.

> Then select startup, the third entry is Video error. You
> can toggle between freeze frame and macroblocking
> mine is set to freeze frame.

I changed mine from freeze frame to macroblocking some time back - I feel it's easier on the eye and I've got a feeling the sound carries on if it's unaffected by the video error. When you get an error, freeze frame will hold the last known good frame, probably until the next I frame comes along - possibly half a second of frozen picture. Macroblocking allows the corrupt picture through, which will further corrupt with each non I-frame until again the next I frame comes along and the picture will clear up.

As for amplifiers, you can't tell if you need one from the strength meters on the boxes, it needs a proper digital signal meter to tell. The amplifier can't put back signal that isn't there, it's only good to boost the signal prior to a cable run so there is no overall loss or to overcome interference along the route.

Thanks all for your responses - I was unable to get on the web yesterday.

I had a look in the service engineers menu.

The salient details appear to be:

oad override off
video error freeze frame
unit temperature approx 40
hdd temperature approx 37
fan speed approx 2100

The signal strength was always 10 and the quality between 8 and 9.

I will try formatting the hard drive to see if that makes a difference - once I've exported out current record history.

I'll also give macroblocking a go to see if that makes a difference

I also performed a hard disk test and that was OK.

Pushing the signal through our dvd player didn;t seem to make a difference - but looking at the replies it looks like our signal quality is OK (signal strength may be too high).

I agree with others that macroblocking is less annoying visually. However, I doubt that it will have any effect on the sound. I also doubt that reformatting the drive etc could possibly have any effect (to the point where I would say don't bother, unless it is in no way inconvenient!)

The problem with Freeview (until the analogue signal is switched off) is that the transmitted signal is rather weak, and prone to being drowned out by impulse interference from a variety of sources. Your amplifier is going to boost these too. Too much gain may even make the problem worse.

Your observations about dropouts on live versus recorded material are interesting. I've long suspected the same, but have tended to reject the possibility because it conflicts with what I think I know about how the machine works!

However, thinking about it again, there clearly is a difference in the live versus recorded bitstream. Consider this: you have to tell the machine if you want to record subtitles. Most of us will have reluctantly switched that function off, because the last version of firmware broke the buffer replay function if you had it set to on. So if you are viewing live, you can have subtitles. If you are playing from a recording, or from the buffer (e.g if you rewind) you cannot. It follows that the bitstreams in the 2 cases are not the same, and that your observation may well be correct (and independent of any other hardware factors).

@socrateesside

In a recent post you are considering a format of the HDD, in that case you could try the above first which you can do easily with just the top cover off (no need to remove any screws, or loosening of the front panel). Worth a go.

pzboyz

...and on the question as to whether the playback can be worse than live: we often have stuttering sound after rewinding a bit of recording on FVRT200, and last night the picture also stuttered and pixelated and, for a brief spell, the sequence was also disordered. As usual a short pause put things right, but clearly there were other factors at work than poor reception in the first instance because the recording was clean when first played back

The distortion we get is definitely happening at the recording point. Rewinding the program and replaying has the distortion and sound dropouts at exactly the same point each time you play.

I've had it on Macroblocking for a weekend now and there is a chance it has had some effect. The picture now goes through more pixelation and bizarre colour changes but and although we do still get an amount of corruption to the sound it hasn't gone on for as long as it was doing previously. So my guess is that the box is displaying as much of the signal as possible rather than dropping out chunks of the program.

One other thing I forgot to mention was that sometimes when the corruption occurs part of a line of dialogue in a program are repeated. i.e. the picture goeas a bit iffy and for example a 3 second period of sound is repeated.

I've not yet tried opening the lid to reseat cables. I was going to refoprmatt the disk through the engineers menu - but given that the disk check appears to be OK I'll open the box up later this week to check the wiring.

Thanks again everyone for taking the time to read this.

An update:

Although it's not perfect Macro Blocking does appear to have had a siginificant impact on the issue.

Although we now appear to get more frequent pixelation this is not in any way as distracting as the sound problem. We do still very occasionally get sound problems but I'm quite happy to live with the level of problem we are now seeing.

Thanks all for your help