BOOT CAMP 522 (29/04/08)

Internet TV and the BBC iPlayer part 4


Viewing TV programs streamed or downloaded from the Internet on a PC is all very clever but with the best will in the world a computer monitor in the office or spare bedroom is not the same as watching telly on a big bright TV screen in the comfort of your own living room. Since the launch of BBC iPlayer earlier this year a growing number of readers have been asking how to connect their PCs and laptops to their televisions, so over the next two weeks we’ll show how it is done.


It should be simple, and for some it is, but in most cases there are two fundamental problems, namely location and compatibility.


Laptop owners are off to a good start since they can have their computers close to the TV but most desktop PCs are usually some distance away, often in a different room or floor. The obvious difficulties are linking the PC to the TV, and controlling the computer, so you don’t have to get up out of your comfy chair every time you want to start, stop or pause playback. However, before you can even begin to worry about such things the biggest challenge is the difference between the video signals coming out of the average PC and the video input connections on a television receiver.


If fact there is around a dozen different types of video connection in use on computers and consumer video equipment – see this week’s Top Tip for a small selection -- and they’re all incompatible with one another. Only two of them can be relied upon to be present in all cases, though not always in the right place at the same time....


The standard video interface on pretty well all Windows, Mac and Linux computers is the VGA output socket. The signals it carries are analogue in nature and comprise red, green and blue picture information, plus synchronisation (sync) pulses. It’s a reasonably simple arrangement but it was originally designed for delivering text and static graphics displays to CRT monitors. Over the years there have been many improvements and it is perfectly capable of carrying decent quality video but it is far from ideal. There are a number of limitations the most important of which – for desktop PC owners – is a restriction on the length of connecting cables, to around 10-15 metres. It is possible to extend cable length beyond that but it starts to get a bit complicated, and expensive.


The only video connection that you can be sure of finding on all TVs (and VCRs, satellite receivers and digiboxes) is Composite Video. It’s also an analogue type signal but this time the picture information and sync pulses are mixed together and carried by a single conductor in a shielded cable. Composite video connections are very simple and the signals travel quite well over cable lengths of 50 metres or more. However, the amount of information a composite signal can carry is limited and it’s not the first choice where picture quality is important, on high-end and high definition TVs, DVD and HD players, recorders and digiboxes, though, in the application we are considering here it’s not a critical issue.  


It goes far beyond differences in plugs, sockets and picture signals, though, and the images you see on your PC screen and television are produced in entirely different ways and the bottom line is that unless your TV and PC both have the same types of connections, some form of signal conversion is going to have to take place – more about that next week.


It’s not all doom and gloom, though, and we’ll round off this week with the best case scenario, which would be if you have a laptop and a flat screen LCD or Plasma screen TV. If so you’re probably wondering what all the fuss is about. To begin with there’s no need to worry about controlling a distant computer since it is sitting next to you and cable length clearly isn’t be a problem.


Many laptops have a composite video output so the only other thing you’ll need is a suitable AV cable. Typically this will have a phono (video) and minijack plug (audio) at one end, and a SCART (input type) plug at the other. These are widely available from TV and PC suppliers in lengths up to 10 metres from around £10.


The laptop’s display has to be switched to ‘TV out’, usually by pressing a Function key on the keyboard, and you may need to select the appropriate AV input on your TV. You might have to experiment with the PC’s resolution settings and the TV’s aspect ratio controls, to make sure the picture isn’t stretched or squashed and fills the screen properly.


If your laptop hasn’t got a composite output you should still be able to hook it up to your LCD or Plasma screen since most models made within the past five years have a VGA input socket. All you need is a VGA extension cable, and an audio lead of similar length. After connecting both cables set the TV to PC input mode and start playback. The majority of TVs automatically configure screen shape but again, you may have to fiddle with the PC’s display settings. VGA picture quality on flat screen TVs can be a bit variable and this is down to the TV’s processing circuitry and screen design, rather than your PC so there’s not much you can do about it, other than upgrade your TV.


Next Week – Internet TV and the BBC iPlayer part 5





Syndicat des Constructeurs d'Appareils Radio Recepteurs et Televiseurs – Euro standard audio and video connection system



Timing signals that ensure the stability of TV pictures and PC displays



Video Graphics Array - standard PC display format




In addition to composite video, consumer video devices may also be fitted with S-Video (aka Y/C Video), Component Video (YPbPr), RGB, HDMI (High Definition Multimedia Interface) and DVI (Digital Video Interface). DVI actually began as a PC to LCD screen connection system and you’ll find it on some high-end models. Digital video data can also be transported between devices using FireWire and USB connections.


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