All posts by Michael Perry
Below are all of Michael Perry's postings, with the most recent are at the bottom of the page.
Briantist
The dreaded errors are back!
This page displays as:
[redacted]
But the main section is accessible, hence this message.
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Use the Knoweldgebase to find answers to your technical problem
Saturday 11 October 2014 9:56PM
Trowbridge
Saturday 11 October 2014 9:56PM
Trowbridge
Further to what Briantist and Brian Gregory have said, there is a major problem with synchronisation of content delivered via different media. In all distribution systems there are delays due to the physics of the communication methods used. Even the old fashioned postal service has delays, as does delivery via courier but a letter normally arrives quicker if sent via RM than via Courier. So with TV distribution, delivery via an RF transmitter standing on the ground has natural delays due to atmospheric propogation, distribution via a control centre, microwave links, etc. Those delays are generall slightly shorter when compared to a satellite system. That has an inherent delay as the signal has further to travel (up to the satellite, through its electronic systems and retransmitted for reception on the ground again). Those delays are typicall around 4 seconds, using the Atra satellites as an example, and almost all that delay is in the uplink and downlink path.
The internet has its own inherent delays due to propogation either along a copper wire or through a fibre optic connection. Then there are delays in the servers that control and distribute the data streams like On Demand TV. Those delays vary from quite short, maybe around 2 seconds on a good service to well over 20 seconds in some cases.
Try an experiment with your internet service and an AM or FM radio. Set both to deliver BBC Radio 4 at 6 PM and listen for the 'pips'. You will find that the FM and AM are almost together, but the internet has a noticeable delay. Ypou can add the satellite version of Radio 4 and see how much greater the delay can be over FM. DAB also has a longer delay than FM or AM. It's all due to physics of communication.
So now imaging trying to synchronise TV pictures delivered by two different methods. With differeing delays that are actually quite variable and somewhat unpredictable, there would be a mind blowingly difficult problem of how to 'dovetail' all the data together to make a single coherent picture without strange and disturbing visual artefacts!
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Use the Knoweldgebase to find answers to your technical problem
Sunday 12 October 2014 9:16PM
Trowbridge
Sunday 12 October 2014 9:16PM
Trowbridge
Briantist:
Before I wrote that I did the test myself. My AM and FM radios differ by so little it is hard to discern. The DAB radio I have, a not expensive one, had a delay of about .3 seconds, noticably more than the AM & FM services but less than the Internet. My Internet was about 0.6 seconds delayed but that varies by about 0.2 seconds over time. The Sky satellite signals have a delay of approximately 4 seconds almost entirely due to the propagation time needed to cover the 80,000 km for the up and down links. The internet signals are digitally encoded, as are the satellite signals, so I suspect there will be little difference in the delays introduced during encoding and decoding.
The real point was that trying to 'interleave' the signals delivered via different transmission media may well prove the stumbling block to the idea of having HD via DVB-T (or DVB-T2) or satellite and then adding in the extra data needed for 4k that is delivered via a totally different route with different, and non-static, delays. As an electronics engineer, I cannpot see a way of overcoming the variability of the delays that are inherently different. If we could, it's an idea worthy of investigation.
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Phreddy
the Conwy Valley transmitter is a Freeview Lite service and hence you only get the PSB services, the commercial services are not planned to be available from that site. Look at the P's DigitalUK trade link adjacent to your post. Only if you are able to receive decent signals from Llandonna would you be able to get the commercial services, but my memory of that area includes sizable hills to the west of you iun the direction of that main transmitter.
You are already getting all that you are paying for, the license is to permit you to operate a TV receiver and everyone pays the same irrespective of whether the commercial operators chose to provide their programming.
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Briantist
I know just how much work has been involved with all you have done recently - and am aware of some of the problems that needed to be sorted out.
As for the emails, I personally preferred the 'old' layout as I got quick access to discussions I have contributed to and to other realted that might have been of interest. Now I find I have to go searching for anything bar the very latest of my entries, though I would often like to consider offering help to others problems if only I can find them! Not a criticism but meant as a helpful comment.
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Briantist
I liked the style you used for the emails up until 10/10/2014, up to last week in other words.
That layour allowed us to quickly find most, if not all, the new questions so we could judge whether we could offer a constructive response to help the enquirer. It also included on the right some links to related questions. We could still navigate throughout the site if we wanted, as we can now, but the email links were a quick way to get in and try to help.
I'm sure you have some of the 'old' style emails, but if you don't I can supply via email.
BTW, not had an email tonight. It used to arrive soon after 7 PM, then that dropped back to 8 PM and then 9 PM. As I write it's almost 10 PM. Any reason?
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Use the Knoweldgebase to find answers to your technical problem
Tuesday 14 October 2014 10:09PM
Trowbridge
Tuesday 14 October 2014 10:09PM
Trowbridge
Charles Stuart
To do that would require every frame to be uniquely identifiable so that matching HD frames can be paired with their 4k counterparts. As the system currently used does not have that unique identifaction ability there is no way to combine them without serious visual artifacts that would be even more disturbing that the pixilation we already see.
The ability to store numerous frames is not so much of a problem these days, memory is relatively cheap for large amounts (that is for RAM memory and not hard disk type) and the electronics needed to control it all should not be an insurmountable problem, it's the lack of ID per frame that is the 'stumbling block' currently.
Some years ago, the firm I worked for wanted to make a 'video wall' before they became commercially available. The main problems we found were that digitisation was far too slow in those days (1980s) and data storage was not only slow by extremely expensive! We even discussed the ideas with both BBC and Central TV (I worked in the East Midlands) and they were interested in the ideas as they were trying to develop the same for theiur studios - but they were finding the same problems. Modern electronics has overcome the speed and cost so we now have video walls all around. But they have not solved the interleaving problem yet either.
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W Sass
Can you watch any of the other HD channels on COM7? Do you have an HD capable receiver that has a DVB-T2 tuner that is able to receive and show all the HD channels?
If you don't have a DVB-T2 equipped TV or set top box then you will not get any HD services.
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M Bevan
Does your TV have the DVB-T2 facility? Do you get BBC1 HD? If not then your equipment probably can't receive the HD multuiplex, COM7 and hence can't get MotorsTV.
If your equipment is FULL HD (and not just HD Ready) then you may need to check that it is set to use the DVB-T2 transmissions.
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Thursday 9 October 2014 11:12PM
Trowbridge
Mark
The Naish Hill transmitter is nowhere near Corsham! It is south south east of Chippenham but is not 'visible' from my new address in Trowbridge due to hills, particularly at Chaveywell and Holt.
As you can see from the response above to Briantist, the UKDigitalRadio: Coverage website is of no practical use in this case.
'Drilling down' into the website reveals a map showing transmitter locations - but not coverage.
At my 'old' address, on a hilltop 4 miles north of Calne, our reception from Naish hill was terrible to non existent! Even MW was very variable at best! FM is poor and DAB suspect in most rooms of the old house. I was hoping for better reception without resorting to a directional aerial on top of the UHF and FM aerials plus the satellite dish! It gets terribly unsightly and 'the lady of the house' doesn't like all the 'hardware' on the roof/chimney stack!