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HINTS & TIPS

 

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STAIN REMOVAL

Name              Stephen Thomas Brown, Chester-Le-Street, Co-Durham

Kit                   Toshiba 32 MW7DB

Problem            Stephen is having a spot of bother with a Toshiba 32MW7DB TV. The first one had a lot of greenish colour staining on the screen. An engineer from the shop said it was due to 'magnetic interference' and it would go away in a week or two. It didn't and after six weeks another engineer called and he said the TV had been dropped and arranged to have it replaced. A new TV was delivered and this one had blue colour staining in the left-hand corner of the screen. Another engineer called and he said it was magnetic interference again, this one reckoned he could get rid of it, or move it to another part of the screen with a degausser. Not wanting two colour patches on the screen Stephen declined the kind offer and now wants to know what to do next?

 

Expert Reply             Colour staining occurs when the thin perforated metal sheet inside the tube behind the faceplate, known as the shadowmask (or aperture grille in the case of Trinitron and Diamondtron tubes), becomes magnetised. It can happen naturally or by accident (the TV is shipped with a consignment of loudspeakers, for example); it can even be caused by the earth's magnetic field.  Normally it does go away as every time the TV is switched on the tube is automatically 'degaussed', by a coil attached to the outside of the tube. This induces a collapsing magnetic field in the tube which effectively 'erases' residual magnetism on the shadowmask. Occasionally the magnetic field is too strong for the TV's auto degauss system and it has to be manually cleared, using an industrial strength degauss coil. Stephen should have taken the engineer up on his offer. The engineer was also right about physical shock causing colour problems; a heavy knock can result in the shadowmask becoming misaligned. However, the fact that he has had two TVs on the trot with this problem is very unusual. Stephen says there are no nearby speakers or metal objects that he is aware of but he should check that there are no hidden magnetic fields. A good quality compass might reveal the presence of a field from underground cables, pipes or structural metalwork.

 

TV/VCR AND SATELLITE QUERIES

 

OUR NORWEIGIAN PAL 

Name              Truls Heilo, via email                          

Kit                   Panasonic NV-F77 VCR   

Problem            Norwegian student Truls Heilo moved recently to the UK to continue his studies, bringing with him his trusty Panasonic NV-F77 video recorder. He has now discovered that the PAL system used in Britain is not the same as that used back home because he can get a picture, but no sound. He says the weird thing is that videos brought in this country play back okay on his machine, when it is connected to an amplifier. He wants to know if there's a solution?        

 

Expert Reply             Possibly. Here in the UK we use the PAL I system, Norway uses PAL B/G. The difference is very small and concerns the separation of the picture and sound subcarrier frequencies in the broadcast TV signal. (PAL I is 6MHz, PAL B/G is 5.5MHz, see Getting Started this month). The only component in a VCR affected by this frequency difference is the RF modulator that plugs into the aerial lead. It converts the incoming TV signal from the aerial into separate video and sound signals for recording, and back again during replay through the aerial lead. The reason Truls can play a British bought tape on his Norwegian VCR is because the difference in the various PAL systems are irrelevant when using a direct AV connections to the TV and amplifier, since the signals bypass the RF modulator. It should be possible for Truls to have a UK spec PAL I modulator installed in his machine at a reasonable cost by an engineer with access to scrap Panny machines but a new part installed by a Panasonic service agent could work out quite expensive.

 

BUCKS AND BANGS

Name              Marc Osborne, via email                          

Kit                   interested in a Panasonic TV

Problem            With a budget of £3500 Marc wants to know what is the biggest bestest TV he can get? He has been tempted by the Panasonic TX47PT1 47-inch rear projection model and he likes the look of the 36-inch TX36PF10, but he wants to know if a rear projection TV gives as good a picture as a CRT set. The rear projectors he has seen at various stores have always been poorly demonstrated with a weak signal so that he remains to be convinced, one way or the other.       

 

Expert Reply             We're not about to tell Marc how to spend his money, the bottom line is that if he wants a TV screen size larger than 36-inches then he has two choices: a projection TV of some kind, or a Plasma screen. At the moment the latter is well outside of his budget. Large screen TVs always involves some compromises. Rear projectors, even ones as a good as the TX47PT1, have a narrower viewing angle than a CRT and they work best in subdued light. It's also worth bearing in mind that projection TVs have shorter working lives and/or higher running costs than conventional sets.

 

BORDER DISPUTE

Name              Steven Hunter, via email                          

Kit                   Panasonic W28D2P widescreen TV      

Problem            After some cajoling the dealer that supplied Steven with his Panasonic W28D2DP widescreen TV agreed to replace it after he complained about the screen changing display ratios of its own accord. However, now the new TV is doing the same thing. Steven says Panasonic TVs are in short supply in his neck of the woods so has he been unlucky and got caught with two from the same duff batch or do all widescreen TVs suffer from this problem?        

 

Expert Reply             This type of behaviour is not unusual on widescreen TVs with automatic aspect ratio adjustment systems. It has to do with the way these TVs decide display format, in the absence of any switching or ident signals from broadcasters. The TV looks for other signs, such as black bars at the top of bottom of the picture. If the picture or scene has dark borders then this can confuse the TV into thinking the picture has been letterboxed and will change picture shape accordingly. There doesn't seem to be an easy answer except to switch screen shape manually or go digital, where – eventually – aspect ratio switching will be fully automatic.      

 

SUPER SUSPECT

Name              Chris Burmajster, via e-mail

Kit                   JVC HR-S7500      

Problem            According to Chris there has been a lot of talk in Home Entertainment about the JVC HR-S7500 Super VHS video reorder. He was impressed and brought one. He has notice that on several occasions we have said that the quality of off-air recordings is no better than ordinary VHS, but why? Surely, he says, if a TV broadcast has 600 odd lines then an S-VHS VCR should capture 400 of them, as the format's resolution is 400 lines? This is the same as laserdisc, so the picture should be the same as laserdisc, but it isn't.

 

Expert Reply             It's not quite as easy as that and it can be a bit misleading to talk about lines of resolution in connection with off air TV pictures. Resolution is a measurement of a recording, replay and display system's ability to record and reproduce fine detail. As far as TV broadcasts are concerned the amount of information or detail in an image is determined by the system's 'bandwidth' (for analogue transmissions) or 'bit rate' and 'compression' when talking about the digital TV. 

 

The short and rather simplistic answer about the performance of video recorders is that when we make judgements about the quality, or otherwise, of a TV picture the first thing our eyes and brains are aware of is the amount of noise. Surprisingly our ability to perceive picture detail is not that well developed, we may say a moving picture looks sharp and crisp, but what we're really observing is the lack of noise and grain in the image. When we measure detail we have to use specialised static test signals and charts, that show up fine detail.  The VHS and S-VHS recording systems are both analogue and both are inherently noisy. Noise is introduced at almost every stage of the recording and replay process and by the tape, but one of the biggest sources of noise in a VCR is the UHF tuner. The extra detail that an S-VHS VCR can capture is effectively masked by noise. To illustrate that point, consider a recording made on an S-VHS-C camcorder. They look so much cleaner than off-air recordings, even if they're copies, simply because the signals do not have to pass through the many conversion stages and processes in a tuner. Further proof of this effect can be seen on digital video recorders, which can get very close to 'off-air' quality. The tuners and input stages on these machines are more or less identical to the ones on analogue VCRs, and just as noisy, but since the video signal is made up of numbers noise is ignored, so more detail and less noise ends up on the tape. 

 

BOX COPY 1

GETTING STARTED

By now you are probably aware of the fundamental differences between the NTSC television system used in the US (Japan and parts of the Far East) and the PAL system which we use in the UK and throughout much of Europe. However, as one of this month's letters illustrates, there is still plenty of scope for confusion since there are several flavours of PAL. In fact the analogue colour television systems used throughout the world are designated by letter – A through to N. The letter indicates a number of technical parameters including the number of picture lines and fields displayed per second. It details the frequency of the colour subcarrier Information used to decode a colour signal), the separation of the video/audio subcarriers, (the difference in frequency between the channels sending the picture and sound signals) plus the vision and sound modulation. These last two determine how the picture and sound signals are configured.

 

In case you were wondering the basic specs for PAL-I are as follows: 625-line/50-fields, 4.43MHz sub carrier, +5.5MHz video/audio separation, video modulation is negative going and sound modulation is FM. The US NTSC-M system is: 525/60, 3.38MHz, + 4.5MHz, negative, FM. The standards list contains some oddities, like the now defunct SECAM-E system (819/50, no colour subcarrier, +11.5MHz, positive, AM), then there's our old, and equally obsolete friend British System A:405/50, no colour subcarrier –3.5MHz, positive, AM sound.

 

You might think life is complicated enough in the UK with TVs, VCRs and DVDs able to play and display NTSC and PAL software but we've got it relatively easy. You can tell a lot about a country's colonial past and recent history from its TV systems. Cyprus for example uses both PAL and SECAM systems, reflecting British and French interests. Vietnam has NTSC and SECAM systems. Russia, the former Soviet Union and most former Eastern bloc countries use the French SECAM system. This one goes back to the cold war, the USSR decided not to develop a colour TV system of its own but opted for the French system in preference to American NTSC and PAL, which was developed in Germany.

 

DVD AND LD QUERIES

 

STAR LETTER

 

THAT SYNCHING FEELING

Name                          Daron Wild, via email **                     

Kit                               Pioneer DVD-515, Sony STR-DB925 AV receiver

Problem                      He's not sure if he has a connection problem, something wrong with the set-up on his Pioneer DVD-515 player, or there is a known problem with discs or decks, but Daron is upset with DVD. He says some discs play perfectly whilst on others the soundtrack is just slightly out of synch with the characters lip movements. Daron says the worst offender is 'Lock Stock and 2 Smoking Barrels' where the synch wanders in and out, so much so he says that the movie is unwatchable.  

 

Expert Reply             Join the club, we have had quite a few letters from disgruntled Pioneer DVD owners, and not just those with the DVD-515, there have been similar complaints from users of the 717 as well, and a pattern has started to emerge. Lock Stock… seems to be the worst offender by a long way though it appears there may also problems with Con Air and Region 1 imports of Lost in Space. And that's not all, we have heard of similar problems affecting other brands of player. Initially it was thought that it might have something to do with 'chipped' players or disc mastering but after speaking to a Pioneer spokesperson we can now report that it is a fundamental problem with its decks, and the outlook is not good. It concerns the way DVDs are mastered. There is a small time difference – no more than a few milliseconds -- between the picture and sound on all discs, normally it is so small as to be inconsequential. However for reasons that we have yet to get to the bottom of, Pioneer decks randomly exaggerate the time difference, and it can grow to as long as one and a half frames, which is more than enough to cause a loss of lip-synch. Some reports suggest that dabbing the fast forward button when it happens gives a temporary cure, but it will usually come back again. Pioneer tell us that as soon as the problem came to light its engineers looked for a cure by revising the deck's firmware (the built in software that controls how the machine operates) but quickly discovered it was not possible. Pioneer told that a 'fix' is not possible on current models. Pioneer say that it only affects a very small number of discs and the problem has been exaggerated by various reports in magazines and on the Internet, maybe so but we would like more information. If you have had synch trouble with Pioneer machines -- or any other brand for that matter -- and discs not mentioned please let us know. We'll keep you posted.  

 

UNHAPPY TRAILS

Name              Scott Gamage                                                         

Kit                   Sony DVD-715, Philips 32PW9763, Denon SVR2700       

Problem            On 18 or the 35 DVDs in Scott's collection he has noticed that when things move in the picture it leaves a 'trail' and faces have a ghost-like appearance. The worst offender is Crimson Tide, Scott says it happens randomly, sometimes every 5 to 10 minutes, or it could happen four or five times in a minute but not start again for another 20 minutes. He returned the player to the dealer that sold it to him, they reported no fault found but replaced the player anyway. The new deck started doing it again a few weeks later but instead of taking it back to the shop again, this time he checked and changed his connections. He has tried every possible connection method but still no joy. He is wondering if it has anything to do with the fact that his Sony DVD player has been chipped?

           

Expert Reply             This could be caused by a number of things including multi-region modifications but in this case our guess is this could be the result of an interaction between the DVD and the TV. The fact that it doesn't happen on the dealer's bench seems to confirm that view. We have seen something quite similar on other widescreen models and the common factors have been automatic or dynamic noise reduction systems, digital video processing or 100Hz displays. Since we haven't tried this particular combination of components we can't say precisely what is happening and why, but it seems that for some reason the TV detects what it considers to be a picture aberration and winds up the digital processing, producing the characteristic trails. Scott should try switching off any automatic picture processing and noise reduction options on the TV and see what effect that has on the picture.

 

DTS DILEMMA

Name              Richard James, Wentloog, near Cardiff                           

Kit                   Denon AVC-3800 AV amp, Panasonic DVD-A350 DVD player   

Problem            After upgrading his Denon 3020 to the 3800 Dolby Digital AV amp Richard is now thinking of replacing his DVD player. He has two questions: one, is it worth going for DTS and two, if so, which player should he buy?  He likes the look of the Pioneer 717 but the new Sony model sounds quite promising and he is a big Denon fan.     

 

Expert Reply             A few months ago we would have said that if you were in the market for a DVD player and provided it didn't add significantly to the price DTS was an option worth having. Maybe not for now, but for the future when there might be a wider choice of DTS encoded discs. On a good day, with the right disc and the wind in the right direction DTS can sound noticeably better than Dolby Digital – the power and resolution of the effects and sub-woofer channels are very impressive. Things have begun to change, nowadays you would be hard pressed to find a new DVD player without a DTS enabled output, it's even starting to appear on budget models. Richard will also need a DTS processor to go with his amp, and there too there have been some developments with processors like the Denon AVD-100 coming in at under £300. Unfortunately the supply of DTS discs hasn't improved, there are between twenty and thirty Region 1 discs available from the US and a handful of Region 2 samplers but thus far the names and dates for any Region 2 releases is being kept under wraps. Richard should be keeping an eye on DTS developments but we don't think the market has developed sufficiently to justify ditching what we suspect is a perfectly good player just yet.

 

WRONG KONG

Name              Gerry Laff, via email                                   

Kit                   Panasonic DVD-L10 

Problem            Whilst on holiday in Hong Kong Gerry happened upon a Panasonic DVD-L10 portable DVD player. It was a Region 6 model but it has since been modified to play Region 2 discs. The only problem is, the video output is NTSC only. He wants to know if swapping a chip or two can change this, or will he just have to put up with it?

 

Expert Reply             As far as we're aware, and we're prepared to be told different, altering the video output on the L10 would involve major surgery. It probably entails changing the whole AV processor board, and that would cost almost as much as the player is worth, so the short answer is yes, he will have to live with it.            

 

FADED GLORY

Name              Dean Stevens                                  

Kit                   Sharp XV-320P video projector, Pioneer DV-414 DVD player, CLD-D515 LD player 

Problem            Dean is not a happy man. He purchased the DVD player (an NTSC model) along with a selection of discs (Armageddon, The Perfect Murder, The Truman Show) and is now regretting it. The problem is the picture, via the Sharp projector, fades from light to dark several times during each scene. The DVD player works fine through a PC card on his TV, and on a friend's Sony television; he has tried different connecting leads but all to no avail. He emailed Sharp but their response was to ask him if he was using 'proper software'. A friend with the same video projector has since told him that they are having the same problems, this time with a Panasonic DVD and PAL discs. Until the glitch is sorted out Dean says he will not be purchasing any more DVDs nor recommending the format to his friends due to it being such a rip-off!

 

Expert Reply  Changes in picture brightness is a characteristic of the Macrovision anti copy process applied to a lot of DVDs (see Getting Started). It is designed to nobble VCR recording from DVD by generating out of tolerance signals that confuse the video recorders automatic gain control systems. TVs are designed to be a lot more tolerant of wonky signals and will usually ignore the anti-copy signals. Video projectors on the other hand do not have tuner 'front ends', and in the normal course of events do not have to deal with anything other than clean, unadulterated video signals. On somne DVD players it is possible to switch off the Macrovision encoding and there are various devices on the market --  variously known as 'enhancers' and 'processors' -- that may be able to neutralise some or all of the effects of Macrovision but it's by no means assured as the process works on several levels. If Dean has an Internet connection it shoudl be worth his while to check out the postings in DVD newsgroups and visit the sites of companies that specialise in modifying DVD players for multi-region playback.

 

DANCING SCREEN

Name              Paul J Coghlin, Sudbury, Suffolk                                   

Kit                   Pioneer 315-1 AC-3 LD player, Sony KV28W1TV, 

Problem            Has anyone else noticed an annoying problem during playback of PAL discs on the Pioneer 315-1, asks Paul J. Coghlin? He says he can see faint 'dancing lines' of varying width, clearly visible in the background. They usually occur in fairly dark scenes or indoor shots and seem to be part of the recording. Repeat playback shows the lines to be in the same place every time. Paul says they show up clearly in Start Trek First Contact, in Chapter 3 during the scene where Picard and Riker are in the Captain's ready room discussing why they're not chasing the Borg. The lines appear behind Riker and Paul says once you're aware of them you start noticing them. Other discs affected include Dante's Peak, Independence Day, Titanic and Jurassic Park. He has also spotted lines using a Pioneer 2950 LD and Toshiba TV, though not as many as on his Sony TV. 

 

Expert Reply  This is a new one on us and we're keeping an open mind. We would be interested to hear from any other HE readers who have also seen the mystery lines on the discs mentioned, on other titles, or have any idea about what they might be. Over to you.  

 

BOX COPY 1

GETTING STARTED

BOX COPY 2

MACROVISION COPY PROECTION

The Macrovision anti-piracy system works on the basis that televisions tolerate brief interruptions or interference to a broadcast TV signal whilst VCRs react much more quickly to changes. Macrovision protection on DVDs works in a slightly different way to tape. The picture signal on the disc is stored as 'clean' digital data, Macrovision spoiler signals are added by the player during the digital to analogue processing stage, an instruction code on the disc switches the Macrovision signals on and off.

 

Macrovision operates in a number of ways. The basic technique is to periodically reduce the amplitude of certain synch pulses by around 25% and add 'pseudo' synch pluses and extra pluses of varying amplitude, cycled every few seconds, that trick the VCRs automatic gain control. This is known as Level 1 processing and produces a characteristic pulsating brightness effect. Level 2 processing involves modifying a part of the colour video signal called the 'colour burst'. This only occurs on some picture lines and once again the disruption will usually be ignored by a TV receiver but a VCR will be upset by the errors and the recording may suffer from 'venetian blind' colouring, with bands of colour, or no colour at all, across the picture. Macrovision coding can be defeated and various types of 'processors' and 'stabilisers' appear from time to time, moreover it is possible to deactivate the coding chips in some players but Macrovision continually modify and extend the system and most Macrovision 'Busters' tend to have fairly short lives.

 

---end---

Σ R. Maybury 1999 1105

 

 

 

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