HD live picture break up now HD mux is on offset channel

[MarkAL]

I have a Humax HDR Fox T2 (Cust FW 3.13) which has been suffering from HD picture break up for 18 months at least. The problem occurs when watching live HD TV which effectively rules out a problem with the drive. It might happen once or twice during a 1 hour program, and the next day I might never see the fault all evening. Of course, once the problem has been witnessed live, hitting rewind will show that the live picture break up has been recorded too.
I had already replaced the drive before I realised that the random break up occurs on live TV.
I never see a problem with SD recordings.
I’ve checked the state of 12V, 5.8V and 5V rails and all are good. Nevertheless I replaced all power supply electrolytics, but the problem persists.
I am receiving HD TV on PSB3 mux C35- (585.8MHz) from Winter Hill but the HDR Fox T2 is set to C35 (586.0MHz). Prior to June 2022 HD TV muxes from Winter Hill were com7 on C55 (746.0MHz) and com8 on C56 (754.0MHz) – no offset channels.
Current C35 signal strength is 71% and quality is 100% - I’m assuming that the quality dives when the picture breaks up but there’s no way of monitoring signal information for hours on end.
I’ve tried replacing the loft distribution amplifier, downlead, patch lead and using different gain outputs (8dB, 12dB and 16dB) on the stepped gain distribution amplifier but nothing makes any difference.
I’ve got to think that the momentary break up is due to the fact that the tuner is programmed to receive on 586.0MHz and it momentarily loses lock on the 585.8MHz transmitted frequency.
Prior to June 2022 there was no offset between transmitted and programmed receive frequencies for HD muxes from Winter Hill.
Can anyone tell me if the 200KHz discrepancy between frequency of transmission and programmed frequency of receiver might cause the tuner to momentarily lose lock?
If so, can anyone suggest a tweak to improve tuner lock?

 

[Black Hole]

It's a shame you didn't talk to us first – you've wasted a lot of time, effort, money, and probably sanity, barking up wrong trees.

The problem occurs when watching live HD TV which effectively rules out a problem with the drive.

Does it? There are ways it can, but probably not in this case.

I’ve checked the state of 12V, 5.8V and 5V rails and all are good. Nevertheless I replaced all power supply electrolytics, but the problem persists.

It's not wise to fix what ain't broke – you risk breaking something else in the process. The only reasons we have ever found to replace capacitors is the HDD reboot loop, and dead PSU.

The engineering principle is to consider what else would also be affected if some particular subsystem were faulty, and clearly faults with voltage rails, or faults in aerial distribution, would not affect only one mux, especially when that mux has a very decent (but not excessive) signal strength.

I’ve got to think that the momentary break up is due to the fact that the tuner is programmed to receive on 586.0MHz and it momentarily loses lock on the 585.8MHz transmitted frequency.

This seems like a plausible hypothesis, but not a dead cert. It could just be a coincidence, and wouldn't "losing lock" be a more frequent occurrence? The first step should be to check whether anyone else echoes this experience from Winter Hill.

I am receiving HD TV on PSB3 mux C35- (585.8MHz) from Winter Hill but the HDR Fox T2 is set to C35 (586.0MHz). Prior to June 2022 HD TV muxes from Winter Hill were com7 on C55 (746.0MHz) and com8 on C56 (754.0MHz) – no offset channels.

DVB-T2 rather than HD TV (HD requires T2, but T2 is not restricted to HD). I presume you are not saying that prior to June 2022 you didn't have BBC B!

 

[MarkAL]

Thanks for picking this up so quickly.
You’re right – I’ve invested a lot of time and effort in this – money less so – but I like a challenge.

Given that the problem is so intermittent I’ve tried to do a lot of diagnostics and rule out as much as I possibly could. I didn’t want to post here to receive a helpful suggestion within hours only to have to take a couple of weeks before I can post a reply to say whether or not that suggestion made a difference.

I’ve used Maintenance Mode to check the Toshiba P300 3TB SATA III drive which was fitted back in May 2020 and all checked out ok, but in February this year I swapped it for a Toshiba S300 4TB drive, so I’m pretty sure there’s no problem with the drive.

Prior to June 2022 the only offset channel from Winter Hill was C54- (PSB3 mux on 737.8MHz) still a T2 signal, predominately mainstream HD channels.

I have always received ALL channels broadcast from Winter Hill, on all muxes, before and after June 2022. It’s just that I’ve noticed the picture break up, on HD only, in the past 18 months. At first I only noticed break up on recordings, which was very tempting to attribute to a disk problem, but I’ve seen the picture break up problem with 2 different drives fitted (both drives pass Diagnostics ok) and now that I’ve been looking harder at live TV, I see that live HD TV picture breaks up.

I have another HDR Fox T2 in the house, also running Cust FW 3.13 and that’s operating without glitching – the only difference I can see is that it’s showing signal strength approximately 4% higher than the problem box in the living room.

 

[Black Hole]

I have another HDR Fox T2 in the house, also running Cust FW 3.13 and that’s operating without glitching – the only difference I can see is that it’s showing signal strength approximately 4% higher than the problem box in the living room.

...which is something you could have mentioned before. Are you running simultaneous recordings so you can check that when one glitches the other does not?

There should be no problem with a signal reading 70%. There should be no problem with the frequency shift, because the actual frequency will be dialled in during the tuning scan (I imagine – perhaps there is a way to interrogate the tuning database @prpr?). If one glitches and another does not, that is a smoking gun unless there is a very localised source of interference.

I see that live HD TV picture breaks up.

As I said, file system faults are perfectly capable of disturbing the HDR-FOX sufficiently to interrupt live reception, but I think there is enough circumstantial evidence that is not the case here.

 

[Rodders53]

Tuner offset will be well inside any Automatic Frequency Correction (AFC) circuitry within the bought-in tuner blocks that the -T2 uses. The number displayed will just be a limitation due to some lookup table within the software Humax wrote for the display of it.

NB Offsets are +/- 167 MHz (possibly 166,666.6 recurring Hz in reality) so you're rounding the number to what you might expect/want the box to display.

My transmitter Sandy Heath uses 21+ (or 474.0 MHz in Humax display terms) for BBC B with no such effects observed. S = 81% when last retuned.

There must be some localised interference or connection issue to the problem box. It will be a royal pita to find.

To start, I'd probably swap the two boxes over to see if the problem stays with the box or the location.

 

[MarkAL]

Yes, I tried simultaneous recording for the first time with "Sherwood" on BBC ONE NWstHD at 9:00pm on 25th August. I was watching live TV through the HDR Fox T2 in the living room (problem recorder) and saw the live signal break up. Of course that picture break up was captured on the recording, but the equivalent recording on my back up HDR Fox T2 was glitch free.
As far as local interference sources are concerned, mobile phones are kept away from both Humax boxes but my Router is only 2m away from the living room box. It's a Linksys gigabit router which was installed in June 2021. I'm a big believer in wired networking so I could try disabling 2.4GHz and/or 5GHz wifi if you think that might make a difference?

 

[MarkAL]

It really helps to be able to bounce ideas around!

Absolutely right – I should (and will now) swap the 2 recorders around and see what happens. The only reason I’ve resisted is because the 4TB box has all the historic recordings which we’re working our way through far too slowly.

It might be a day or two before I can report back...

 

[prpr]

HD requires T2

It doesn't actually. That's just a policy that has been applied in the UK. It's perfectly possible to transmit HD over DVB-T. It's just a data channel.

perhaps there is a way to interrogate the tuning database @prpr?

Of course, you can just look at it with WebIf or the command line sqlite3 tool.
Deleting and re-scanning the mux. with a manual tune will soon tell what the Humax software actually does. I've never been in an offset region to try it.

NB Offsets are +/- 167 MHz

I think you mean kHz old bean!

 

[MymsMan]

Personally I rarely watch/record HD programmes because we live opposite woodland and the HD channels seem the most affected by any interference.
It has been better since the aerial was moved to a pole that is just above the tree line.

The source of your problems could be outside the Humax!
Are all of your TVs/recorder fed from the same source?

 

[MarkAL]

All TVs and recorders are fed from a Labgear SDA263 (or Labgear SDA2061K - I've tried both) loft distribution amplifier, which is fed by a short cable run from an external Antiference 20 element RX20TM aerial covering T band (Ch21-60).
No trees in the way and Winter Hill is "almost" line of sight - hiding just below the roof line of nearby houses.

 

[bottletop]

I find the HD channels I receive are more susceptable to local interference than SD channels. Eg is the problem box near an old fridge/freezer, a boiler or even a horrible light switch? But the suggestion of swapping boxes should give you a great clue.

 

[Black Hole]

The only reason I’ve resisted is because the 4TB box has all the historic recordings which we’re working our way through far too slowly.

That's really not an issue with the content sharing abilities of the native firmware or the improved abilities of the CF.

 

[Black Hole]

Tuner offset will be well inside any Automatic Frequency Correction (AFC) circuitry within the bought-in tuner blocks that the -T2 uses. The number displayed will just be a limitation due to some lookup table within the software Humax wrote for the display of it.

I'm not sure what you mean here. The tuning data won't be coming out of the tuner live, it will be what got sent to the tuner in the process of channel scanning. If frequency offsets are accommodated simply through AFC, the back-end system won't even know there is an offset.

Of course, you can just look at it with WebIf or the command line sqlite3 tool... I've never been in an offset region to try it.

Here's the tuning set from my HDR4:

(I don't know why the captured Q is so poor on some of those muxes)

Anyway, the point is that those Mynydd Machen muxes on 23 and 26 should read 23+ and 26+ (apparently since 2013, I'm sure I must have retuned since then!). I have scoured the Internet to find out what the actual broadcast frequencies are for Mynydd Machen, but I can't find anything which acknowledges UHF23+ is any different than UHF23 (ie 490MHz).



Meanwhile, channel.db says:



...ie no sign of frequency offsets, and offset frequencies must be relying on the AFC. (TBL_SVC refers out to TBL_TS, meanwhile freq.db contains the same info.)

Which implies some inadequacy in the components which implement the AFC could be responsible for poor performance when receiving offset transmissions, and if so the problem should follow the unit rather than the unit's location.

 

[prpr]

I don't know why the captured Q is so poor on some of those muxes

What does the netIdx value 3 report for usNetId in TBL_NET?
You appear to have Wales, West and something else.

Apart from that, it looks like it needs a re-tune.

 

[Black Hole]

What does the netIdx value 3 report for usNetId in TBL_NET?

You appear to have Wales, West and something else.

UHF33 is misreported, I'm pretty sure that's from Mendip (but the Freeview coverage checker is off-line at the moment). Certainly my other machines report it as "West".

Apart from that, it looks like it needs a re-tune.

It does what I need it to do.

 

[MarkAL]

Thanks for all the input. I’ll see if I can post Tuned Multiplex Information” for both recorders, later.

It’s been a week since I exchanged locations of my 2 HDR Fox T2 recorders.
The glitch prone (occasional HD picture break up) recorder has been moved from living room to spare room and the faultless recorder has been moved from spare room to living room.

Same recordings were scheduled on both recorders.
I have watched 6 x half hour recordings (all BBC2 HD) made on the problematic recorder, now in the spare room by using “Network” as the Media source on the recorder in the living room. Of those 6 recordings, 2 recording were faultless and then picture break up occurred once during playback of 3 recordings and twice in 1 recording, at points 11mins, 0.5min, 14mins and 16 & 22mins into recordings.

Rewinding and playing back showed that the picture break up was recorded break up – and this recorder suffered the same occasional break up when viewing live HD TV.

The same recordings were reviewed on the faultless recorder, paying particular attention to points were picture break up was seen on problem recorder but the picture was perfect on the good recorder.

The picture break up fault has stayed with the recorder so I guess that eliminates localised interference as the source of the problem.

I generally end up retuning both recorders every couple of months, as the Freeview channel line up changes. I use manual retune selecting only those channels broadcast from Winter Hill: C32, C34, C35-, C29, C31, C37, C27, C24

Given that picture break up problem was first seen on the one recorder more than 18 months ago,

I’m sure it isn’t a result of a retune that I’ve done.

Any ideas where to look next?...

 

[Black Hole]

The same recordings were reviewed on the faultless recorder, paying particular attention to points were picture break up was seen on problem recorder but the picture was perfect on the good recorder.

I presume you mean recordings made at the same time, not the same recordings. I'm pretty sure the same recordings exported to the "good" HDR would have the same defects on playback.

So far as I can see you have isolated the fault to one particular HDR, and the nature of the fault seems to confirm your original diagnosis... but I'm not sure there's anything you can do to fix it.

 

[MymsMan]

I know you have already tried switching drives without noticeable difference but it would still be worth running fixdisk in Maintenance mode to confirm that there are no problems on the disk, retrying from a write error could introduce a problem and a single bad sector can slow the system down.

How full is the disk? If approaching capacity it might be difficult to find contiguous disk space for recordings resulting in more disk head movement

Do you have the undelete package installed? It is known that deleting large recording files can cause glitches in new recordings and live viewing so is best avoided. If you have autodecrypt enabled ensure you enable the option to create backup files to avoid files being deleted during recording, or you could try suspending all auto processing during recording hours

 

[Luke]

Meanwhile, channel.db says:

View attachment 7166

...ie no sign of frequency offsets, and offset frequencies must be relying on the AFC.

With my offset multiplexes it appears to influence columns further to the right.
For your HDR4 what are the values of eOffset, ucLevel and ucQuality, from table TBL-TS where tsIDx is 1 or 2 (i.e. the rows for your offset multiplexes)?

 

[Black Hole]

For your HDR4 what are the values of eOffset, ucLevel and ucQuality, from table TBL-TS where tsIDx is 1 or 2 (i.e. the rows for your offset multiplexes)?

It will be a couple of days before I can tell you for HDR4 specifically, but if the tuning set for HD3 will do you can analyse it yourself: https://hummy.tv/forum/threads/database-browser-problem-on-hd-fox.11367/post-175442