Whenever i watch moving sport especially football I experience much poorer pictu
Brian Butterworth published on UK Free TV What you are seeing is one of the two problems that are well know about the "MPEG-2" system that is used to encode digital TV.
Because of the way the system works, horizontal movement across a crowd requires a disproportionate large amount of data to encode.
Because the bandwidth on Freeview is so limited, and as most broadcasters have decided to have more channels rather than better quality pictures, on most channels the bandwidth is so limited that the effect you see, a blurry mass of blocks is visible.
The sceptical will say that this is simply an excuse to sell you HDTV equipment and channel packages.
The other problem you will see is when strobe effects are used - this will often look like very large black and white boxes.
If these effects trouble you, do not go out and buy yourself a massive TV as they will be simply much clearer to you.
Tuesday, 11 October 2016
nicholas: I think you might be getting things a little muddled.
Sky boxes do still use the transmission lines in the "blanking area" to fool VHS recorders' auto-levelling into making the picture dark and light. This happens only on the RF outputs.
The issue you describe "ghost outline follows the players" is actually an artefact of the MPEG-2 encoding system. A well known and fixed in MPEG-4 problem. Which is why you see it is SD that is always MPEG-2 in the UK and you don't see it on HD, which is always MPEG-4.
The MPEG-2 problem is that "motion blur" from left to right can't be compressed and causes a vast amount of extra data to be produced in the encoder. Because this will either break the bandwidth limit or buffer size, the encoder has to ditch some of the detail. Most of the time this is imperceptible live, but the moment you give people the ability to pause and live-rewind, it is more obvious.
The effect is even worse on lower horizontal-resolution channels (on Freeview) such as ITV4.
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Richard Cooper8:45 PM
MikeB: Hi, MikeB. It is incorrect to state'nobody uses VHS anymore'. My father does, at the age of 90, although he is finding it increasingly difficult to source blank VHS tape cassettes! Richard in Norwich.
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Richard's: mapR's Freeview map terrainR's terrain plot wavesR's frequency data R's Freeview Detailed Coverage
Wednesday, 12 October 2016
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MikeB2:00 PM
Richard Cooper: The tapes can still be found in Poundland. However, recording them is another matter - the bulk of VCR's were not built with digital tuners, and frankly, DVD's look much better, take up less space and are dirt cheap. The last VCR player was made back in June, and nobody has sold one instore for a good 4 years.
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nicholas10:25 PM
I'm sorry,brian ,but i'm right,if you look at the circuit diagram you will see a diode connected to the power
rail.through an inductance and capacitor and what ever else is required.On a lot of boxes,this arrangement
is muted on the radio section,also it could be built in the v-amplifier chips,but believe me its nothing to do
with the encoding arrangements.In vhs in order to comply with copyright issues,the quality of the picture
was restricted and this noise-called expander noise,makes a complete mess of rerecording the content
in order to stop further copying.Its possible to block the noise to make further recordings but i'm keeping
how its done secret .I have also found tv's have this circuit,why,it baffles me,including the wrap around sets,
the sd is degraded,i have a 18year tube set,cause i got sick of this nonsence.Hope youre better,sorry but this
is the truth,the reason is twofold,to spoil rerecording and make u buy HD versions.
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nicholas10:31 PM
Sorry,i didn't read the bit about motion blur,but this is noise,look at closely,it is ragged,blur is fixed,just believe
me,i do the electronic side,tks.
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MikeB11:30 PM
nicholas: 'the reason is twofold,to spoil rerecording and make u buy HD versions.'
Why would you rerecord from a VHS tape, when you can often buy a DVD version in Poundland? VHS is an obsolescent technology, at best. The only VHS tape I've saved is 'Meet the Applegates', because it was never released on DVD. Yes, Macrovision was put on commercial tapes, but thats no secret.
As for HD, that would be Blu Ray, although it still amazes me that the bulk of discs sold in HMV, etc are still DVD's, not HD, even though nobody has sold an non HD screen for a decade.
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Friday, 14 October 2016
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nicholas7:49 PM
Hi,i've tried to give everybody the reason for ghosts around football players,if you can't accept the truth then do what
big business wants you to, just buy the HD equipment,then you wouldnt' have nasty ghosts following the
football players across your screen,tks
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MikeB10:33 PM
nicholas: Isn't the nasty ghosts possibly just artifacts from low rate picture processing? Or is that just part of the conspiracy?
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Saturday, 15 October 2016
MikeP
11:29 AM
11:29 AM
Nicolas:
It is not 'ghosting' as that only affects analogue transmissions. What people are seeing is the effect of a low bit rate transmission, as MikeB suggests. If the bit rate is low then what they transmit is only a full rendition every several fields followed only by difference information. The effect is for there to be a 'stuttering' of the moving image as it traverses across the screen, particularly noticeable on fast moving elements, such as Formula 1 cars, football and rugby players, horses, etc.
It is not a fault but a well known, to electronics engineers at least, artefact resulting from the bit rate being transmitted having been set too low for the programme. The reason they do that is so that more channels can be incorporated within the available data set for a particular multiplex (that can only carry a finite amount of data).
The DVB-T2 transmissions used mainly for HD services is better at displaying moving pictures with less noticeable artefacts such as these. In the future, all Freeview transmissions are likely to use DVB-T2 encoding, which means less of these picture disturbances but viewers will all need equipment capable of receiving HD services, so a full HD set is required and not just an 'HD ready' set that does not have the DVB-T2 capability.
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