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HINTS & TIPS HE 110

 

TOP QUALITY, PLEASE
Q
I have a Sky+ digibox, which, as you are aware, stores programmes in the MPEG format as received from the satellite. Is there any way that these can be written directly to a DVD without the need to decompress and then re-compress? I don't want to lose any quality. The Sky+ box does have a serial interface and a slot for extra modules, so I assume there must be some way of getting at the MPEG files directly?
Ian Cropper

A

There may well be but it wouldn’t be through the serial socket and it would involve some very serious tinkering to the unit’s innards. The reason the Sky+ box doesn’t have a digital AV output is simple, it’s an anti-piracy measure, designed to stop users creating high quality DVD copies of copyright material. Fitting a digital output and allowing users to make recordings directly would also create a legal minefield for Sky and the content providers, especially when it came to pay-to-view events and subscription movies. You can of course record or archive programmes on tape, there is a noticeable loss of quality but it can be minimised by using the S-Video output and an S-VHS VCR.

 

By the way, in case you’re of a technical or curious disposition, and to save you the effort of finding out the hard way, the Sky+ box uses the Windows CE operating system and hard discs are formatted with the PC standard FAT32 system. Basically this means that if you removed the drive from the Sky+ box and connected it to your PC it would recognise the presence of files on the discs, but the actual video data is encrypted, so the PC won’t be able to read or decode them.

 

QUICK TIP

The hard disc drive fitted to the Sky+ box gives around 20 hours of recording time, which should be enough for most people but a number of teccies have managed to get drives as large as 120Gb to work, increasing recording capacity to over 50 hours. The disc only stores programme data, all of the operating system software is kept on a microchip (to ensure a fast boot-up). However, disc swapping is not something you should try at home and you could easily end up with a very expensive doorstop…

 

 

NO GO AREA
Q
I have just read your review of the Hitachi DV-P305 DVD player, however, it makes no mention of the fact that this player will not play home-recorded CDs, audio or video. I am unfortunate enough to own one, and I've tried 12 different media types (that's the 'please go away' solution of Dixons the retailer), and have used four different types of burner with two types of software, so I think it really doesn't work. Or do you know differently?
Ken Waring

A

Surprisingly the facility to replay audio CDs is not part of the DVD specification yet virtually all players can do it because manufacturers rightly regard it as a selling point. However in the early days at least there was no compulsion for players to be able to handle CD-R/RW discs, which in any case is an entirely different format to CD-Audio, (CD-R/RW is known in the trade as ‘Orange Book, see Getting Started). Now it just so happens that a lot of DVD players made in the last year or so can read CD-R discs but this is a spin-off from the increasingly popular MP3 replay feature. As you know MP3 is a compressed audio format and files stored on a PC – downloaded from the Internet or ‘ripped’ from a CD – are burned onto a blank CD-R. Unfortunately for you the Hitachi DV-P305 is a pre MP3 vintage model, built before the feature took off. It is therefore unable to read CD-Rs because of their slightly different optical characteristics (the data ‘pits’ embedded in the disc are less reflective), nor does it have the more powerful error correction system needed; you are going to have to put it down to being one of the drawbacks of being an early adopter.

 

QUICK TIP

It’s easy to forget that DVD is still a work in progress and new developments and enhancements are coming (and sometimes going) all of the time; here’s a few highlights from the first seven years:

 

MPEG Audio – failed Euro rival to Dolby Digital and dts digital surround, still current but a distinct lack of software.

 

dts -- first generation players usually couldn’t handle dts soundtracks

 

DivX – a clever ‘view once’ format for rental use that came and went in 1999

 

Nuon – interactive graphics, only a handful of discs ever produced, finally died this year

 

DVD-Audio – one of two rival high quality surround audio formats, the jury is still out

 

 

PICTURE PROBLEMS
Q
Can you tell me whether a lower contrast value is better than a higher value on a plasma TV (i.e. the values range from 250:1 to 3,000:1)? I also need to know the same for brightness - is a lower CD value better than a higher one?
Do contrast and brightness determine how good the picture quality will be? Essentially, I just want to be able to work out what's the best picture I can get.
Farhan Zafar

A

It’s easy to get tied up with the specs and forget that the best and most sensitive measuring instruments – for assessing video displays at least  -- are our own eyes and brains. Even so contrast and brightness are fairly important factors to bear in mind when shopping for a plasma screen, so perhaps a few words of explanation wouldn’t go amiss. Contrast ratio is a measure of the difference between the blackest black and whitest white the screen can display. The higher the contrast ratio the sharper we judge the picture to be, even if a screen with a lower contrast ratio is capable of displaying more fine detail. In short the higher the number the better and you should certainly shortlist panels with a ratio of 1000:1 or more.

 

There are various ways of expressing the brightness of a video image. For example, projectors are rated by light output or ‘luminance’ in lumens, whilst a display screen, such as a plasma panel is said to have ‘luminous intensity’ and this is measured in ‘candlepower’ or candelas (CD) per square metre (cd/m2). Once again the more the merrier and recent plasma screens are typically in the range 400 to 700 cd/m2. Incidentally, this obsession with contrast ratios and brightness levels is a fairly recent phenomenon and you’d be hard pressed to find similar figures in CRT-based TV specifications. That’s because until very recently plasma panels had very poor contrast and brightness and they’re only just starting to match the performance of CRTs.

 

QUICK TIP

Whilst the raw data in the specs can give you a fair idea of a plasma screen’s capabilities you can easily get bogged down and in the end the best way to judge picture quality is to see a panel in action, preferably alongside several other screens for comparison. You should also have a good idea of what you want to use it for, to avoid paying for too many unnecessary features, and go armed with a list of the connection details of all the video equipment you want to use it with.

 


Q
I have just purchased an apartment in Spain and would like to take my old Hitachi TV to install there. Can you tell me if our televisions are compatible with the Spanish system and how to tune into the Spanish/European channels?
R. L. Machin

A

The short answer is no, your TV won’t work in Spain but we couldn’t possibly leave it at that so stand by for the somewhat longer answer, with a couple of possible solutions. Here in the UK we use the PAL I colour television transmission system, which basically means a 625-line/50Hz picture and the video and sound signals are transmitted on the UHF band, with a frequency separation of 6.0MHz. Most of the rest of Europe, including Spain, but with the notable exceptions of France Russia and former eastern bloc countries, use PAL B/G. (France and the rest use the SECAM system). The only significant differences between the three flavours of PAL – i.e. I, B & G -- are the separation of the video and audio signals (5.5MHz for both B and G) and the use of the VHF broadcast band (specifically PAL B). What that means in practice is a PAL I television should get a picture in a PAL B/G territory, but you won’t get sound (or the other way around, i.e. sound but no picture), and you won’t be able to receive any local channels broadcast on the VHF band or via some continental cable TV systems. It may be possible to find a local firm to modify the TV for you – it’s a relatively simple business for an engineer with access to the right parts -- but it’s not something you could tackle yourself. The alternative, and this might even work out cheaper, would be to buy a Spanish video recorder. If you connect this to your TV by SCART cable it can act as a tuner, it would also allow you to playback videos (bought locally or from the UK) and to timeshift Spanish TV programmes or satellite channels.

 

QUICK TIP

The PAL colour system is very widely used throughout the world with most countries using the B/G variants for broadcasting but for some reason PAL I – the version we in the UK are blessed with -- is comparatively rare. If you’re thinking of emigrating or buying property overseas we have prepared an exhaustive list of countries you can safely take your TV and VCR to (they also have the same 220/230 volt 50Hz AC mains supplies). In alphabetical order they are: Gambia, Hong Kong, Northern Ireland, the Seychelles and South Africa.

 

 

THE RIGHT IMAGE

Q
I have a Vidikron Projector TV, which has a mass of inputs for use as a monitor; at present it is used in CVBS mode. I understand I would get a better picture if I were to use RGB. The Vidikron has two types of input for RGB - a nine-pin female plug marked "TTL - RGB" and there are also four RCA plugs marked ‘Red Blue Green and Blk’ respectively. I have a Sony VTX S760U digibox, which, according to the meagre instruction book, has RGB output. It reads as though this RGB output is through the SCART plug but does not say which pins are used. There is also a nine-pin female plug the same as the Vidikron but marked RS 232. Does this carry RGB the same as the Vidikron? Basically - how do I hook all this up?
Richard Stoakes

A

Firstly do not connect the 9-pin plugs on the Sony digibox and projector, in fact never connect things together that you are not one hundred percent sure about, very bad things can and often do happen! The ‘TTL’ RGB input mentioned on the projector (it stands for transistor-transistor logic) is a digital computer video display standard, also known as CGA/EGA (colour graphics adaptor/extended graphics adaptor). The other RGB labelled sockets is almost certainly for an analogue computer display system (it would have been helpful to know the model number, so we can check for sure), if so this is used for the monitor connection on older Apple Mac computers. Although the RGB video format used by PCs and Macs is broadly similar to that found on domestic video equipment, like DVD players, TVs, projectors and digiboxes etc., but they are not necessarily compatible. There are adaptors but the conversion process would almost certainly cancel out any improvements in picture quality.

 

Unfortunately, in the absence of a compatible RGB connection or an S-Video socket you are limited to the composite video connection that you are already using. By the way, the 9-pin socket on the Sony box is for a serial data connection (RS-232 is a communications language or ‘protocol’), and is meant for engineers for diagnostic purposes or to update the device’s software.

 

 

SONY SURROUND

Q
I recently purchased a Sony DAV-S800 system, which I rigged up to my television (a Panasonic model), and I am very happy with the results. DVD playback vision and surround sound is perfect. I have an S-Video to SCART connection to AV2 of my TV to achieve this. My query is as follows: how can I get surround sound from the DAV-S800 for normal television programs?
I have cable TV, which is connected to AV1 via the satellite box. Can you advise as to what cables go where, to channel the sound via the DAV-S800?
Hugh Valentine.

A

Many TV programmes and movies broadcast via satellite carry analogue 4-channel Dolby Surround information embedded within the stereo soundtracks and the same applies to a lot of terrestrial TV channels. With the surround sound information encoded into the NICAM audio channels. However the makeup of the sound channels on cable TV can be a bit variable and you will have to contact your local supplier, to find what sort of audio signals they’re squirting down the line.

 

In the case of analogue surround sound information on satellite channel soundtracks all you have to do is connect the stereo audio outputs (a pair of phono sockets) on the back of the satellite receiver, to an auxiliary input on the back of the DAV-S800 (another pair of phono sockets) and set the mode selector to Dolby Pro Logic. If you get no joy from the cable company – and it’s surprising how difficult it can be to get even apparently simply technical information out of some of them – and your cable box also has a pair of stereo output socket on the back (most recent ones do) then it’s worth connecting them to the Sony box in the same way as the satellite receiver and seeing what you get. 

 

 

MAGNETIC PERSONALITY

Q
I hope you can help me. I have a pair of Tannoy floor speakers, which I use for my home entertainment. Unfortunately they are not shielded and cause colour distortion on my TV. I have to put them far apart but my lounge is not spacious. How do I magnetically shield the speakers?
Philip Lau

A

Theoretically it can be done but it would probably be cheaper, and a whole lot simper to buy some new speakers. There are basically two methods of magnetically shielding speakers. The first one involves encasing the speaker magnet in a magnetically conductive shroud or case. It works a bit like the ‘keeper’ bar on a horseshoe magnet and confines the magnetic field to the speaker assembly. The other method uses a second magnet, known as a ‘bucking’ magnet, mounted behind the main magnet, which bends the magnetic field back in on itself. Some AV speakers use a combination of both methods. It’s not something you can easily do yourself, at least not without affecting the performance of your speakers. Shielding the TV is also a non-starter as this would involve encasing it in a magnetically impervious material (the most efficient is an exotic alloy known generically as ‘Mu Metal’). Of course you could replace the TV, plasma screens are untroubled by magnetic fields but on balance new speakers are probably your best bet.

 

 

QUICK TIP

Virtually all CRT-based colour TVs and monitors have a built-in ‘degaussing’ system, designed to neutralise the build up of low-level magnetic fields on metal components inside the picture tube. On most sets this works automatically at switch on, before the picture appears, with a ‘collapsing’ magnetic field. This is generated by a applying a rapidly decaying AC voltage to a coil of wire attached to the rear of the tube. It’s a shame you can’t see it, the degauss field creates a brilliant display of colours, more entertaining than a lot of TV programmes…



Q
We are in the process of trying to identify any standard VHS or S-VHS video recorders that can record Page 888 Teletext subtitles. We would be most grateful for any help that you can give regarding this matter.
Kevin Taylor, RNID Technology

A

From a technical standpoint recording analogue Teletext subtitles or ‘888’ data carried by analogue terrestrial TV channels is not that difficult and many current VCRs have a fair chunk of the circuitry needed to do it but it’s obviously not considered to be a selling point and in the past only three manufacturers, Hitachi, Philips and Panasonic, bothered to develop it as a feature. Some video recorders, notably ‘high-band’ analogue VCRs using the S-VHS recording system and DVD recorders have the capability to record the whole Teletext datastream, which includes subtitle data but again it’s not something manufacturers appear keen to exploit so unfortunately, the official line is that at the moment no VCRs are able to do it. Unofficially a couple of S-VHS VCRs and some DVD recorders might be able to, but it’s certainly not an advertised facility.

 

The situation is somewhat different with digital satellite broadcasts and here you don’t need any special equipment to record subtitles, any analogue VCR or DVD recorder can do it. However, unlike Teletext 888 subtitles, which are decoded and displayed by a Teletext TV, digital satellite subtitles are decoded by the set top box and inserted into the picture so they’re part of the recorded image – see Getting Started.

 

 

GETTING STARTED 1

BY THE BOOK

Although it sometimes seems that the companies behind CD and DVD make it all up as they go along both formats are governed by a rigid set of specifications known as the ‘Books’. The books are colour coded and the original CD-Audio spec is known as the Red Book. CD-ROM and a sub format known as CD-ROM XA is covered by the Yellow Book. The now virtually obsolete Video CD format is defined by the White Book, which also includes Karaoke CD and Super Video CD. The Blue Book describe another little used format called Enhanced CD or CD Extra and the Orange Book is devoted to the CD-R and CD-RW recordable formats plus other specialised ‘Multisession’ discs such as Photo CD. The specs for the short-lived CD-i (the ‘i’ is for interactive) system are contained in the Green Book.

 

Having run out of colours the books defining DVD were assigned letters, thus far A to E have been used up, doubtless with more to follow. Book A is for the original read-only DVD-ROM format used to store computer data. Our particular area of interest, DVD-Video, comes under the auspices of Book B and the DVD-Audio is dealt with in Book C. DVD-R, the write once recordable format is defined in Book D and the recipe for the re-writable formats DVD-RAM and DVD-RW can be found in Book E.  

 

 

GETTING STARTED 2

TV SUBTITLES

At the moment three subtitling systems are in use on British TV channels.

 

Analogue terrestrial TV channels (BBC 1/2, ITV1, C4 and C5) use Teletext, which uses digital data inserted onto unused picture lines in the video signal. The data is decoded by the TV and overlaid on the picture. Because page 888 subtitles are part of the picture signal they are also present when the channels are rebroadcast by satellite. The few VCRs in the past, which could record Teletext subtitles either recorded the whole video signal, including the Teletext data for the TV to decode, or had additional circuitry that recorded just the subtitle info.

 

Subtitle data on digital satellite channels is carried separately in the datastream (the situation with digital terrestrial broadcasting has yet to be resolved). Digital satellite subtitle data is decoded by the set-top box receiver and overlaid onto the video output. Video recording devices that record the digital datastream, such as the Sky+ box also record subtitle data by default, so subtitles can be displayed by the unit’s internal decoder during playback. Other video recording devices, such as VCRs, DVD recorders and hard disc drive recorders like TiVo simply record the sat box’s video output so if the subtitle facility is switched on they will be recorded as well and permanently ‘burnt’ into the picture.

 

Closed Captioning is an American system but subtitle data is embedded in many US TV programmes and some movies shown on analogue and digital TV channels. CC data is similar to Teletext in that it is carried in an unseen part of the video signal, specifically in line 21 of the vertical blanking interval. A separate decoder is required to display the subtitles and one was incorporated into a VCR manufactured by Hitachi a few years ago but this is no longer in production.

 

---end---

 

Ó R. Maybury 2002, 1609

 

 

 

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