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QUERY OF THE MONTH

 

SETTING THE STANDARD

Name                          Alistair Meads, Newark-On-Trent              

Kit                               Ageing 21-inch Hitachi TV, Thorn NICAM VCR, Pioneer D515 LaserDisc player

Problem                      Having decided to replace his Hitachi TV with a 28/29-inch NICAM set, Alistair wants one with SECAM capability; he says he has access to a French VCR.  He has noticed that few TVs seem to be able to work with SECAM signals, apart from a couple of Mitsubishi and Grundig sets. He wants to know why more TVs don’t have it?

 

Expert Reply             There’s really not a lot of call for televisions that operate on the SECAM standard in this country. There’s probably a few in homes dotted along the South coast, where they can pick up French TV signals, but generally speaking it’s not a sought after feature. It’s doubtful whether Alistair actually needs a SECAM TV at all, since he lives well out of range of any French TV broadcasts, and even though he has a French VCR. The differences between PAL and SECAM are mainly concerned with the way colour information is encoded and broadcast. Both systems use the same 625-line/50Hz display scheme so to save cost, and keep life simple, PAL and SECAM VCRs use exactly the same method of recording video and audio signals on tape. In other words a VHS recording of French television programmes, made on a French VCR, will replay on a British machine without any problems.

 

TV/VCR AND SATELLITE QUERIES

 

PHONES AT HOME?

Name                          Kevin Slack, via Email              

Kit                               Vivanco FMH 6800 wireless headphones, Philips 29-inch DPL TV, Sony NICAM TV

Problem                      After reading about the FMH 6800’s in Home Entertainment Kevin immediately dashed out and brought a pair. He complains of a high-pitched whistle when they’re connected to the TV, but it disappears when watching a video. The whistle comes back when it’s used with the tuner on his hi-fi, but it’s fine on CDs. Kevin also says there’s a lot of background noise and is generally a bit peeved.

 

Expert Reply             Kevin clearly doesn’t hang around. We’ve only just received the first production review samples of the FMH 6800 -- see this month’s First Runs. I have to agree that some background hiss is present, but we found that by jiggling the input and volume levels, it wasn’t too intrusive. As far as the whistle is concerned, this sounds like some kind of external RF interference -- probably a harmonic or parasitic signal creeping in somewhere. Our test samples were affected by a nearby TV transmitter on at least one of the three switchable channels. The question is, is Kevin’s whistle being received by the headphones, or is it being picked up and re-broadcast from the transmitter module? The latter seems to be the most likely route since the whistle comes and goes according to the source component. He should try moving the transmitter and connecting leads well away from the TV, VCR, hi-fi, and any other electrical device, and use a different mains socket. If all else fails contact the Vivanco technical helpline, on (01162) 531638.

 

TITANIC CHOICE

Name                          Bruce Evans, Portsmouth                

Kit                               Interested in large back projection TV

Problem                      Bruce is torn between the Pioneer SD-T50 and Sony KL-40W back projection TVs. He’s looking for a screen that will compliment the Dolby Digital sound system he’s hoping to buy.

 

Expert Reply             If only life were that simple. We think Bruce’s shortlist is a little too short and should include the wonderful Toshiba 48PJ6DB, which has a 48 inch screen, and gives one of the best pictures we’ve seen on a back projector. If pressed on the other two then the Pioneer would get out vote. Good though it is, digital processing on the Sony set generates some vision artefacts, and the LCD display elements haven’t as wide a contrast range as the CRT projection tubes used on the Pioneer TV.  

 

NASTY NTSC

Name              Mark Enright, via Email                          

Kit                   Ferguson D78N TV, Pioneer LaserDisc      

Problem            Mark chose the Ferguson TV to compliment his front-room home cinema, which he says is decorated in ‘1960’s Art deco style’.... Work that one out. Anyhoo, the problem is poor NTSC replay, with dark vertical lines. The supplier says Ferguson reckon the TV is within spec but Mark is not happy and says he could argue that it’s not ‘fit for purpose’.

 

Expert Reply             We reckon Mark is on shaky ground with this one. The ability to display an NTSC signal has nothing whatsoever to do with receiving PAL television broadcasts, which is the primary purpose of a television set sold in this country. Manufacturers tend to be quite careful and list any NTSC functionality as a secondary feature, unless the TV in question is specifically billed as a ‘Multi-Standard’ model. They rarely make claims about the quality either, other than to say it won’t be as good as a normal PAL picture. That’s because it’s a spin-off,  video decoder chips are made for an international market -- to simplify the design and save costs -- and can be persuaded to process NTSC signals. Some TVs do it better than others and where possible we make this clear in our reviews. When we looked at the D78N back in September 1994 our reviewer was fairly lukewarm and commented that the picture was ‘soft’.

 

WIDE WORRY?

Name              Simon Pilsworth, via Email                                      

Kit                   Philips 32PW9763 widescreen TV, Ferguson FV105 VCR   

Problem            When Simon plays widescreen editions of movies on his Philips TV he can’t get the picture to fill the screen. He has tried all the zoom modes, to no avail and want’s to know if this is normal. He wonders if it is anything to do with the VCR. He has seen machines listed with ‘16:9 replay’ and would like to know if his machine is one of them?  

 

Expert Reply             This query pops up on a fairly regular basis, and it’s not difficult to understand why as VCR manufacturers continue to promote this wholly useless feature in their literature. 16:9 replay on a VCR sold in this country is completely meaningless. The idea is that when fed with specially recorded anamorphic tapes, the VCR will switch  widescreen TV to which it is connected, to the relevant display mode. Anamorphic processing -- as applied to video -- is where a widescreen picture is electronically ‘squashed’ to squeeze it into the space occupied by a regular 4:3 picture. When viewed on a normal VCR and TV, everything looks tall and thin; suitably equipped widescreen TVs stretch the picture back, to its normal proportions. Since there are no anamorphic tapes available in this country the whole business is academic.

 

When it comes to showing widescreen versions of movies on a 16:9 TV, the picture is electronically inflated to fill the screen, but most movies are actually recorded in a format that’s wider than 16:9 --  it was chosen as a compromise for all the many different widescreen formats -- so the picture often has thin black bands at the top and bottom of the screen.           

 

BACK TO SPOOL

Name                          Ben Tyler, Portsmouth                

Kit                               ancient Amstrad VCR

Problem                      Being a remarkably patient man Ben, has put up with his old Amstrad VCRs funny ways and mediocre picture quality, but it has recently taken to chewing tapes and is now retired. Unfortunately it devoured his treasured wedding video; the transparent leader tape has been torn from the take-up spool. He want to know if it can be repaired, and if so is it a job he can tackle himself?

 

Expert Reply             If the actual tape had been damaged I’d suggest you pay to have it properly fixed but since it’s a detached leader, you can try and do it yourself, provided you’ve got a small Philips screwdriver, a pair of sturdy tweezers and steady hands.  The first step is to remove any labels on the back, or lightly score through the centre of the label with a sharp craft knife, along the line where the top and bottom halves of the shell meet. Turn the cassette over with the drive sprockets uppermost. Remove the five screws and without separating the shell, turn it back over, with the hinged flap facing away from you. Gently lift off the top half of the shell, giving it a little wiggle as you do so, to stop the rollers and guides coming away from their mounting pillars. In the middle of the take-up spool you should see a little curved wedge piece, that’s accessible through a slot in the wheel. Lift it out with the tweezers. Next re-thread the leader, being careful not to touch or crease the magnetic tape. As it comes off the feed reel it goes between a metal pin and a springy wiper tab, then around the outside of a metal guide post, across the front of the cassette and between a second metal guide post and roller. Lay the end of the leader across the gap, where the wedge piece goes, then place the wedge piece over it. Using the tip of a screwdriver, it should snap back into position. Take up the slack by turning the take up spool and replace the top shell. It will seat easier if you slightly open the tape cover. Hold the shells together, turn the cassette over and replace the screws. Don’t over-tighten, you might strip the threads, or distort the shell.

 

BOX COPY 1

GETTING STARTED -- KEEP IT CLEAN

Every time you load a tape in your VCR thousands of dust particles go in with it. Tapes moult too, bits of the coating drop off when it’s passing around the rollers and the spinning tape drum; after a while a fine coating of debris builds up along the tape path and eventually clogs the microscopic gaps in the recording/replay heads. It happens quite slowly, so slowly in fact that you probably won’t notice the gradual reduction in picture quality until it is quite serious. How long this takes depends on the quality of the tape you’re using, and if you rent a lot of movies, which can be badly contaminated. You can stop this happening by regularly using a tape head cleaner cassette. Abrasive ‘dry’ cleaners are fine for routine maintenance, a quick run through every two or three months, should be enough. However, if you experience a sudden drop in quality it’s worth trying a ‘wet’ cleaner, which are better at removing stubborn deposits. Always read the instructions, and only use good quality tape head cleaners, purchased from reputable companies.

 

BOX COPY 2

ENTHUSIASTS GUIDE -- INDEXING, THE FORGOTTEN FEATURE

Pretty well all VCRs have a tape indexing facility, that automatically tags the start of each new recording. If you read the book and find out how to use it you might find it quite useful, especially if you have a number unlabelled tapes, and no idea of what’s on them. VCRs with tape indexing normally have an intro scan function, that works in fast wind mode. When the stationery head comes across the index mark the deck drops into fast picture search for a few seconds, so you can see what you’ve recorded, then returns to fast wind. It’s a feature that’s well worth getting to know. 

 

Index markers are specially configured control track signals. They’re a series of pulses recorded along the top edge of the tape, 25 times a second. The duration of the pulse can be varied to represent a binary ‘1’ or ‘0’. There are two kinds of control track signal or CTL Code: VISS (VHS Index Search System) is the most common and consists of a sequence of 63 pulses, that identify the start of a new recording. The second type is VASS or VHS Address Search System, and this can be used to record small chunks of data, relating to the time and date of the recording, for example. Only a handful of machines have ever used VASS to anything like its full potential, the most recent coming from Sanyo, who call it the Tape Library system.

 

LD AND DVD QUERIES

 

NTSC STUTTER

Name                          Chris Cherrington, via Email                                                          

Kit                               Pioneer CLD-D925 LaserDisc player, Pioneer DV-500 DVD player

Problem                      Chris has recently acquired a LaserDisc player, and an imported DVD deck. He says he’s very impressed with PAL LaserDiscs and has started buying some NTSC discs and thinks AC-3 sound is excellent. Since he has had the DVD player, he has noticed that the picture on both NTSC LaserDisc and DVDs ‘stutter’ when the scene is panned. This doesn’t happen with PAL LaserDiscs, he hasn’t seen any PAL DVDs yet. He thought this might have something to do with MPEG encoding, though this doesn’t apply to NTSC LaserDiscs. Then he suspected digital processing on the TV, but he’s tried it with other, non digital sets, and it’s still there. What’s going on? 

 

Expert Reply             It’s all to do with the way movies are recorded on video,  and the difficulty of transferring films to NTSC; it affects both LaserDisc and DVD. Movies are recorded at 24 frames per second but NTSC video has a frame rate of 30 frames per second. To get around this temporal incompatibility a technique known as ‘pull-down’ is used. It’s a bit involved but basically what happens is this: movie frames are processed two at a time, the first one is shown for two NTSC fields, lasting 2/60ths of a second. The second one is shown for three fields, or 3/60ths of a second. Together this adds up to 5/60ths of a second, or 1/12th of a second, which is the duration of two movie frames (i.e. 2 x 1/24th of a second). This is called a 3-2 pull down. The end result is the jerky slow panning Chris describes. It doesn’t happen when movies are transferred to PAL, picture frames last for 1/25th of a second -- close enough to 1/24th of a second -- so a 2-2 pull down can be used.

 

DIRTY HABITS

Name                          Michael Winters, Hastings                    

Kit                               Looking forward to getting his grubby hands on a DVD player

Problem                      Michael reckons he’s a careless bugger and something like half of the CDs in his collection are either unplayable, or skip, as he can never be bothered to put them back in the case, they get all mucky and scratched. He asks if that’s going to be a problem with DVD, especially as there’s much more information on the disc?

 

Expert Reply             Yes it is, though just because there’s more data packed on to the disc, it doesn’t necessarily follow that smaller scratches will cause any more damage. DVD actually uses far more efficient error correction techniques, that can tolerate bigger losses of data. MPEG compression is also geared up to mask errors, even so, they’re not indestructible and Michael should learn to put his discs away otherwise he will just be chucking his money away.

 

ONE STOP BOX?

Name                          Sandra Teller, Blackpool                  

Kit                               thinking about a high-end CD player, Sanyo TV

Problem                      Sandra was planning to buy a high-spec CD player but has recently been reading up on DVD. She understands decks will also play audio CDs. She wants to know if she should go ahead and get her prized CD deck, or will DVD machines have superior audio CD capabilities?

 

Expert Reply             Compatibility with audio CD isn’t actually in the DVD specification, though all manufacturers are making it a key selling point on their hardware. It’s possible audio will eventually be given a higher priority but thus far it seems that first generation DVD players have no special talents in that area. If top-end performance is a requirement Sandra should stick with her original plan.

 

BOX COPY 1

GETTING STARTED -- BACK PANEL BLUES

How will you hook up a DVD player to your existing AV hardware? European players will be a bit like Super VHS VCRs. There will be one, possibly two SCART AV connectors carrying composite video and S-Video or RGB video. Most models with also have a separate S-Video output, via a mini DIN socket, as well. Later models will be fitted with FireWire IEEE 1394 digital outputs, for direct connection to digital TVs and VCRs. We don’t expect to see any decks with RF or coaxial outputs, there’s no need for an aerial connection moreover it would reduce picture quality, and only mono sound would be available.  Audio outputs will include line-level stereo, that will contain any Dolby Surround information on the soundtrack. There will be a separate digital output, for the AC-3/MPEG audio digital datastream, either using a RF connection (usually a phono socket) and/or an optical digital jack.

 

BOX COPY 2

ENTHUSIASTS GUIDE -- REGIONAL CODING

If you’ve been following the DVD story you will have come across the term regional coding. Essentially it’s a way for the Hollywood studios to control the release and distribution of movies, by ensuring that coded discs will only play on machines in the country they’re intended  for. The world has been carved up into 6 regions: Region 1 is the US, Canada and US territories. Region 2 is Japan, Europe, the Middle East and South Africa. Region 3 comprises East and South East Asia. Region 4 is Central and South America, the Caribbean, Pacific Islands, Australia and New Zealand. India, the Former Soviet Union, Africa and North Korea make up Region 5 and Region 6 is China.

 

 

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