Fullscreen HTML5Med Res (??MB)HTML4

Perhaps you are blissfully unaware of it – but the Australian Government plans to progressively switch off all analog TV transmitters, starting in less than two years time. And High Definition digital TV programs are now being shown on “free to air” commercial, ABC and SBS TV. Those programs are not available via Standard Definition digital tuners or settop boxes. So what do you need to do? Y ou might have seen adverts on the Seven & Ten network stating that their new High Definition (HD) TV programs are now available. New Zealand is also converting, with HD Digital on air in all major population centres, ready for the start of the Beijing Olympics on 8th August 2008. Perhaps you have been thinking that you will be able to get the new HD programs with your existing standard definition (SD) set-top box (STB) or SD digital tuner. Well, think again. It doesn’t work that way. If you want to see HD programs, you will need an HD tuner, even if your present display cannot show them in the needle-sharp focus of HD. siliconchip.com.au In Australia there are HD and SD receivers. SD programming will eventually die out with the advent of HD-only programming but an HD STB can produce an SD signal for analog receivers. So even if you decide to stay with your present analog TV set, it will still be possible to watch all the new high-definition free-to-air programs, provided that you have an HD STB. The clock is definitely ticking on analog TV broadcasts. Senator Conroy, the Minister for Broadband, Communications and the Digital Economy, has set the switch-off date for metropolitan analog TV as December 2009, with all analog transmissions to cease by 2013. So there is no escaping it, if you want free-to-air TV programs in the near future, you are going to have to “go digital” and realistically, that means “go HD”. But why wait? Why not enjoy all the advantages that HD TV has to offer, right now? The main advantages are more programs, much better picture and sound quality and no ghosting. If you want to watch HD programs, you must obtain: 1) A wide screen TV which incorporates an HD tuner or 2) An HD Set Top Box (STB) which will receive digital signals and convert them into a form a conventional receiver can display or a standard March 2008  9 You’ll need an HD set-top box if your TV doesn’t have one built in. But don’t despair: they won’t cost an arm and a leg! This Tevion brand HD STB was on sale earlier this year for less than $100 (see the review in this issue). And we’ve seen them for $50 or less on eBay! video recorder can record via its AV inputs or 3) An HD Personal Video Recorder (PVR). This device will receive digital signals and display on a conventional or wide-screen display (and/or record them if you wish). And while it might seem obvious, you need a suitable antenna to receive the digital signals. Your existing antenna may not be good enough. If you live in a home unit, your building’s Master Antenna Television (MATV) system will need upgrading to pass the channels used by digital TV. The cheapest and best way to do this is for all residents to obtain either a STB or PVR first. They may not receive all stations at this stage. Then get the body corporate/building owner to upgrade the MATV system to digital channels. The installation should be made according to Australian Standard AS1367: 2007. The cheapest option is to install STBs near the antenna instead of retuning the channel amplifiers. One STB will be required for each digital channel. The STBs will be used to convert the digital signals back to standard definition analog. However, this approach will prevent you seeing High Definition signals and multi-channel sound on your expensive new TV. And it will probably prevent you seeing the new HD and the supplementary channels already available. See www.dba.org. au/index.asp?sectionID=26 If you live in a free-standing home or dual-occupancy dwelling, you will need to check to see if you get reliable digital reception, particularly in the rain. Check that the picture does not break up into little squares, the sound not go off and on or that the “no signal” sign appears. If any of these things occur, then you require an antenna designed for digital reception (not “digital-ready”) in your viewing area. The antenna cabling may also need replacing. We hope to have more to say on digital antennas next month. HD set-top boxes are getting cheaper all the time. Over the Christmas period, Aldi stores had an HD STB available on special at just $99 (down from $119) while Coles supermarkets have had them even cheaper at $79. You could also pick one up on eBay for less than $50 (but watch those postage charges!). At the same time, we have seen standard definition (SD) STBs on sale for as little as $35. However, in view of the above remarks about HD programming, we see little point in buying an SD STB. In fact, we forecast that once the general public understands their limitations, SD STBs will shortly disappear from the market. PVRs are also becoming cheaper by the day and they are a very good option if you want to record a HD program at a particular time while you watch another HD (or SD) program. This is easy with most PVRs since they usually have two inbuilt tuners. PVRs are similar to a VCR but with some distinct advantages. The first of these is the Electronic Program Guide (EPG). This is where the broadcaster sends out via their transmissions the names of all programs to be shown for the coming week. You can then select the programs you wish to record by name. No more worrying about start and stop times, channel number etc. Another advantage is Time Slip recording, which enables you to pause the program you are watching, while the recording process continues. You can then start playing where you left off while the recording is being completed. Since the recordings are made on a very large hard disk (typically 160GB or 250GB), there is no waiting for a tape to wind to the right place; it is just like playing a DVD. Here’s the rear view of the STB above. At left is the standard coax antenna input and loop output sockets. Alongside is the coaxial (digital audio) and S-video socket, followed by the Y, Pb and Pr component video sockets (labelled HD OUT). The next three sockets are component video (yellow) and L/R audio (white and red). Immediately alongside this is a D-socket for use with a VGA computer monitor. The next four sockets are the interesting ones: DVI out (for projectors, etc), the HDMI output we’ve discussed in the text; a USB socket for USB devices and finally, the optical, or TOSlink audio socket. 10  Silicon Chip siliconchip.com.au PRIME There are many ways to “skin a cat” – some better than others. If you have the option, the best is to use an HDMI cable to connect a personal video recorder to the TV – especially if it is an HD type. ELECTRONICS Est. 1987 â 115 Compact DMM 3 YEAR WARRANTY CAT III 600V True RMS AC/DC Volts 600V AC/DC Amps 10A Resistance Continuity Frequency Capacitance List Price $245.00 Diode Test Analog Bar Graph Backlight Min/Max/Avg Display Hold Auto/Manual Range Holster Our Price $199.00 179/EDA2 Combo Kit LIMITED LIFETIME WARRANTY CAT III 1000V CAT IV 600V Subtitling for the hard of hearing’s data is also recorded along with the program so you can choose whether you display subtitles on playback or not. HDMI or component video? HD STBs and PVRs should be connected to your TV set or projector by HDMI or component video cables. HDMI stands for “high definition multimedia interface”. But which one should you use? HDMI or “component video”? HDMI has the following advantages: • It can carry the three colour signals and up to eight channels of sound siliconchip.com.au on a single cable. • It can tell the display what type of signals is being sent so that the display can automatically adjust. • It can convey control commands for other devices. So for example, a single remote control can be used to control the PVR, etc. • It can carry the High Definition Copy Protection (HDCP) signals. There is talk of only outputting Full Definition (1920 x 1080p) signals to the HDMI output only. This will particularly affect High Definition DVDs such as BlueRay and may actually be a drawback in the future, as far as most users are concerned, since HDCP is a copy prevention method. Kit Contains ● ● ● ● ● ● ● Fluke 179 True RMS DMM TL224 SureGripTM Silcone Test Lead Set TL910 Electronic Test Probe Set AC280 SureGripTM Hook Clip Set TPAK Magnetic Hanger 80BK Intergrated DMM Temp Probe C35 Soft Meter Case List Price $585.00 Our Price $499.00 Prices exclude GST Call for a 2008 Fluke Catalogue www.prime-electronics.com.au Brisbane (07) 3252 7466 Sydney (02) 9704 9000 March 2008  11 For the complete “home theatre” experience, you’ll need a 5.1 channel amplifier along with the DVD and PVR. While the subwoofer is shown centre rear in this diagram, it can in fact go just about anywhere as low frequency sound is, for all intents and purposes, nondirectional. Y, Pb and Pr signals. The sharpness of the image will be controlled by the resolution of the display but the accuracy of the colour should be a little better using HDMI compared to component video. In essence, your ultimate picture quality will depend more on the resolution and video conversion processes inside your video monitor or projector than on whether you have selected a component video or HDMI cable connection. HDMI uses only one cable • The signals are not converted into analog. This is an advantage because the display will have to digitise component signals, so that the image can be stored for display. Thus digital to analog and an analog to digital conversions are eliminated. • Finally, it allows the transfer of the xvYCC colour signals to the display. This gives a greater range of strong colours, if they are present on the disc. But in spite of the above, there is presently no clear-cut advantage for HDMI over “component video”. While HDMI is a digital format, it does not have error correction and therefore long cable runs can be more problematical, with possible signal dropouts, than the analog “component video” connection. To explain, both HDMI and analog component video deliver signals as three discrete colour components, together with sync information which allows the TV or projector to produce the video display. HDMI delivers these via three data channels in a format called TMDS (Transition Minimised Differential Signalling). The TMDS format basically involves a blue channel to which horizontal and vertical sync are added and separate green and red channels. TMDS involves two schemes to minimise noise and interference. “Transition Minimised” refers to the conversion of the signal to Grey code, 12  Silicon Chip which only has one bit change at a time in the channel. So if interference is picked up, all channels receive it and it is ignored. At the same time, it employs “Differential Signalling” whereby when a “1” is being sent one wire of the pair goes to +250mV while the other goes -250mV with respect to earth. They reverse when a “0” is being sent. This gives noise immunity. Error correction is also applied to the sound and control signals (but not to the colour signals). The signals are sent as identifiable packets, so the same wires are used for picture and sound. An HD colour signal consists of a luminance (Y) signal. It shows as a black, grey and white signal in sharp detail. The picture is then “coloured in”, by using a Pr signal which colours it either red or aqua, or a Pb signal which colours it blue or yellow. The green and purple colours can be derived from the above three signals. Component video is not much different, with the analog colour information also split three ways: luminance (the “Y” or green channel, representing the total brightness of the image); Red minus Luminance (the “Pr” or red channel); and Blue minus Luminance (the “Pb” or blue channel). The horizontal and vertical sync pulses are delivered on the Y channel. The video display calculates the values of red, green and blue from the HDMI does have the convenience of only using one cable connection instead of three in the case of component video (plus an extra two for the left and right audio channels) but when you consider that component video cables are always moulded together to give one flat “cable”, albeit with three RCA connectors at each end, the advantage is small. Nor is there much advantage if you are using a video projector since you don’t have to worry about connecting audio cables (although you do have to connect separate audio cables to the amplifier). HDMI cables are not normally included when you purchase HD equipment and have to be purchased separately – and they are also more expensive than equivalent high quality component video cables. In fact, they are very expensive for lengths between 10-25m. Cheap HDMI cables can be a problem at lengths above 5m, with the most frequent symptom being “sparkles” in the picture followed by complete dropout. For HDMI cables longer than 1015m, you may need an HDMI repeater such as the one sold by Jaycar Electronics (Cat AC-1698 at $79.95). This is powered by a plugpack. HDMI cables also present problems for installers. This is because you presently cannot buy HDMI cable and then fit it with connectors – you must buy the complete cable with connectors fitted at each end. This can make it very difficult to pull such a cable through wall cavities without damage. Long component video leads can also be a problem, especially if they use cheap cable. The result is picture blurring. For projectors, component connections are an alternative to the high cost of HDMI. However, blurring of siliconchip.com.au A selection of some of the cables you’re likely to come across. At left is an S-Video cable, while to its right is an HDMI cable. A composite video cable is next, with its three RCA plugs (yellow is video, red is right audio and white is left audio). Finally, the cable at far right is a combination component video/audio cable – the green plug is Y, blue is Pb and red is Pr. This cable can also handle composite video (yellow) and stereo audio (red and white). the vertical edges in the picture will occur if they are too long. If you have insufficient HDMI inputs then you can use component inputs, but also feed the sound into the display as well. The other option is to use a home theatre amplifier to do all switching, provided it can delay the sound for the delay in the display. In practice, we think that the decision whether to use a component video or HDMI connection will depend on how many HDMI inputs your TV or projector has. At present, video projectors come with only one HDMI input and many HD TVs are the same. So if you have several HD video sources (eg, HD STB, PVR and DVD), you will probably end up using a mixture of component video and HDMI cables. The most recent “upmarket” HDMI plasma and LCD HD sets may have two or three HDMI inputs so there is less of a problem with these models. If you have one of these, it is best to feed all sources to the display, then take the sound from the display. This also has the advantage of avoiding problems with “lip sync” whereby the video is delayed with respect to the sound. By the way, using S-video or composite video cables for HD connections is really a waste of time and money, unless you are using an analog TV set. What about Surround Sound? If you want to get the complete experience, then you also need a home theatre amplifier and all the necessary loudspeakers. If you purchase an HD STB or PVR, it will have a coax or optical output which can be fed to the Dolby decoder in your home theatre receiver. However, consider that unless you frequently watch “action” movies, there is no real need for surround sound; your TV’s inbuilt speakers will be quite adequate for the purpose. Even if you do watch the occasional “action” movie, a good quality stereo pair of speakers and your existing system amplifier can still give a very satisfactory aural result. In fact, if you have a limited budget, as most people do, then our advice is to buy the biggest HD set (or choose a HD video projector) and leave the decision about a surround system to a later date – if ever! If you do decide to go for the full home theatre experience with multiple speakers, go for the best home theatre receiver you can afford. It will also solve any problems with switching of HD signal sources. Most plasma and LCD TVs have stereo sound systems but many have relatively poor sound due to restricted speaker sizes. HD programs are broadcast with the option of two sound systems. The first of these is MPEG2 which is stereo only. The second is AC-3 or Dolby Digital 5.1 which carries six channels: left, centre and right front, as well as left and right rear. The 0.1 is the low frequency channel which is normally fed to an active subwoofer. Typically, when broadcast AC-3 has a greater dynamic range than SC MPEG2. NEXT MONTH: In part 2 of this feature, we’ll look at some of the traps for young players in HDTV reception – for example, is your old analog TV antenna suitable for digital? The answer is . . . probably not! SUPPLIERS OF Contact PH: 1800 331 301 Email: info<at>alvin.com.au Web: www.alvin.com.au siliconchip.com.au Digital STBs’ MATV Systems Audio Distribution Telephone and Data Accessories Digital and Analogue TV Antennas Digital and Analogue Interconnect Cables DA-5000 Digital Antenna March 2008  13