Electronics Australia copyright

I was delighted to hear that Silicon Chip Publications has purchased "Electronics Australia" magazine. Like you, I was saddened to see it cease publication in 2001.

Please accept my best wishes on behalf of all of us at Jaycar Electronics. I look forward to resuming my monthly EA read!

Gary Johnston,

Jaycar Electronics,

Silverwater, NSW.

More on DVD picture quality

I have read with interest some of the recent correspondence in Mailbag with regard to the perceived lack of quality provided by the DVD format and hope that this note will help to clear up matters for the correspondents. I would first direct them to the DVD FAQ at: www.dvddemystified.com/dvdfaq.html

Simon Kareh in the September 2001 edition of Silicon Chip raises two issues:

(1) The fact that Titanic when shown in full screen was not missing any of the picture compared to widescreen and in fact had more picture information.

The reason that Titanic (and some other films) have more picture when shown in full screen 4:3 mode is because of the way it was originally shot on film. Not all films are like this. Directors generally (although not all of them) shoot the film for a rectangular cinema screen (you may have seen footage of a film being shot with the director looking at a video monitor displaying a 4:3 image but with a white rectangular "cinema screen" shaped marking across the middle of the screen).

Typically crew members, boom microphones, etc, that appear outside the rectangle are ignored, because the director knows that the film will be matted for the rectangular shape of a cinema screen. Some directors shoot with release-to-video in mind as well, so while the shot is composed for the rectangular screen, the director makes sure that there is nothing untoward in the frame outside the rectangle.

Widescreen does not automatically mean you are getting more picture (although you are getting the picture the way it was intended) just as full screen does not automatically mean you are getting more picture.

(2) The issue of lines of resolution and NTSC/PAL differences is the other topic. The 500-line video resolution referred to in regard to DVD players is an old analog measurement of vertical black and white lines resolvable, not the horizontal scan lines. The DVD FAQ gives a full explanation but basically vertical lines are not the same as horizontal (scan) lines.

The 480 (visible) and 576 (visible) scan line NTSC/PAL difference still applies. Think of vertical lines as similar to a computer monitor's horizontal resolution (the 800 in 800 x 600). A DVD does approximately 500, while VHS does approximately 230. A DVDs actual on disc resolution is 720 pixels wide by the PAL or NTSC number of scan lines.

With regard as to which is better, the NTSC disc with its higher frame rate or the PAL disc with its more scan lines, that is a whole separate debate that comes down to personal preference.

Brad Sheargold in the October 2001 issue of Silicon Chip questions the quality of DVD after seeing a demonstration on a friend's plasma display. While it is true that there are quite a number of poorly encoded DVD's around, I would suggest that the problem Mr Sheargold was observing might have been to do with the nature of plasma display devices, or that particular devices calibration, than with any inherent flaw in the DVD format as a whole.

From my understanding, plasma devices currently are not very good at producing dark colours. They also tend to have a black that is not true black, rather a grey or brown (although both these characteristics are improving all the time). These characteristics are artefacts introduced by the display device itself and will serve to highlight any MPEG artefacts that may have been present on the disk, although generally artefacts seen are caused by display devices that have not been calibrated properly, have their "sharpness" control turned up, etc.

Another possibility is that the artefacts Mr Sheargold saw were introduced by some kind of low quality scalar or line doubler/quadrupler or, the need for such a device. (Incidentally, the highest resolution Fujitsu plasma device I saw after a brief look at the Fujitsu website was capable of displaying 1024 x 1024, not 1 million x 1 million as his understandably enthusiastic friend told him).

The bottom line is that a bad DVD picture is not always the DVD's fault. I would suggest Mr Sheargold see if he can view those discs on a different display device and see if he notices the same problems.

I watch DVD's on my own modest CRT, and regularly see them on a friend's projector system, an I can honestly say that the DVD on the projector is the best picture quality I have seen outside of a cinema (and even inside many of them!).

In response to John Richardson form his letter in the October 2001 Silicon Chip, I understand that the ABC has been having some teething problems with their new equipment (I have also noticed incorrect aspect ratios that suddenly change, etc).

Mr Richardson's points about the lack of some potential features being utilised have some validity, apart from the quick access - I can jump to chapter stops in DVDs very quickly (granted you do have to sit through the copyright screens on first loading some discs, but then you have to fast forward through them and promos on VHS tapes, so I doubt VHS is any quicker). I suppose it depends on what you define as "quick access".

In regards to the sound quality of DVD, unless you have a Dolby Digital and/or DTS capable sound system then you are only hearing the lowest quality sound that DVD can provide. I expect the DVD consortium will take it as a compliment that the lowest of the DVD is equal to the best of the VHS.

Sam Yates,

via email.

AVR ISP programmer software I have some further information on the AVR ISP Programming Adapter featured in the October 2001 issue. The software mentioned in the article ("AVR ISP", from Atmel) only works with Windows 95, 98 and Me (not NT4 or 2000). It also doesn't support some of the latest AVR microcontrollers. I have discovered another software package that addresses the above issues and should be compatible with the hardware as presented. It is called PonyProg (of all things) and is available for free download from http://www.lancos.com To configure PonyProg to work with the programming adapter, set it up for the "AVR ISP (STK200/300) parallel port interface" as described in the included documentation. As a bonus, PonyProg should also work with the PIC Programmer and Testbed described in January 2001 (use the "JDM" programmer settings). Peter Smith, Narraweena, NSW.

In favour of backups

I always find your articles on computers and software interesting and quite useful but your frequent suggestion to 'wipe' your hard disk and start from scratch quite upsets me!

I can't imagine how you have avoided the serious trap in doing this. Reinstalling all your software is not a simple task, particularly if you have commercial software which you have paid good money for and upgraded frequently. Many programs require the previous version to be on the system before they will install the latest upgrade.

Just the thought of reinstalling all the versions is bad enough however I am using one program that started life on 5.25-inch floppy disks! I do have a 5.25-inch drive but it is years since I used it and the disks are unlikely to be readable even if I could find them. Even the 3.5-inch drive is used so rarely it generally needs kicking to make it behave and I have a couple of programs that started life on them.

Please, in future, place a warning when you give this advice. For many people it may be OK but for some of us - well, it would be disastrous. Instead, I do wish you would suggest people make backups regularly. These days when most (if not all) of your readers probably have CD burners, backing up all the important parts of a hard disk system is not difficult.

I use an old system for backups. The hard disk is split into three partitions (I used to use two disks). The 'C' drive has the system and all programs. I do a backup of this when it is needed, after installing new software. The 'D' drive has all the important data; backup of that is daily if not more frequently. The 'E' drive is for 'junk'!

For added safety, a copy of the 'D' drive exists on two other computers. If you think that maybe I don't trust computers, well I don't. After 35 years of experience I have good reason not to .

Geoff Syme,

via email.

VideoSCope magnification

I have built, with slight modification, the excellent VideoScope project published in the October 2001 issue. My approach differed in that I used a "syringe" type approach with the camera (Dick Smith Electronics L-5873) being on the end of the plunger which is 760mm long. I used a 50mm F1.2 lens from a Minolta SRT101 camera. I am able to reproduce magnification of an EPROM similar to that shown in your article and when viewing a ruler I can get the markings of 1mm to appear full screen width on my 34cm TV (28.5cm horizontal). I intend to try the concept in my microscope and telescope as well.

My question is how do I determine the magnification I have achieved? One would think that if 1mm is shown over the width of 28.5cm then I have magnified the image by 285 but I question this as moving to a different, larger TV the magnification would increase just as the screen size increases.

I am interested in how the authors determined their shot of a silk screen was enlarged by a factor about 3200.

I think that this an excellent project. It was cheap for me as I had all the components, yet extremely practical. I can now show my 3-year old granddaughter things she would have difficulty seeing with my microscope.

Ken Fox,

Vermont South, Vic.

Comment: the effective magnification does depend on screen size. If you have a bigger screen, you get a bigger image. As far as the figure of 3200 is concerned, perhaps the image was taken with a close-up lens.

In your December 2001 issue you published my offer to pass on the electronic parts & instruments which I had accumulated 'over life". The response was amazing, exceeding my wildest expectations. Unfortunately, because I was uncertain if there would be any interest, when an 'early bird' appeared on Tuesday morning, November 27th, and offered to take everything, I accepted, in case I got no more interest. As a result, I have had to refuse many writers, many of whom I would have liked to satisfy. So, I apologise to all those who, though quick off the mark, were too slow. I hope I have written to all who wrote to me. If I missed anyone, please accept my oversight. And, to anyone who has not written but sees the offer, it is too late! Pamela & Ewart Jones, Coromandel Valley, SA.

Macrovision solution

I have a Macrovision solution that is so simple I am surprised no one else has thought of it. What you need is a PC with a capture card and a TV-OUT video card. What I use is a Prolink Play TV Pro Video capture kit and a TNT2 Video card with TV-OUT. The capture card supports watching TV in full-screen mode on the computer.

What I do is Play video 1 onto the PC and have my capture program at full-screen and have the TV-OUT card going to video 2. This not only avoids the Macrovision but removes it totally from the copy.

There is also no generation loss because the video stream re-encoded in the computer so you have a copy of the same quality of the original. I have tried this on about 15 Macrovision-protected tapes without a problem.

Lindsay Harvey,

via email.

Clarification of DVD resolution

Some recent letters have suggested that DVD pictures are considerably better than VCR pictures because of the poor resolution of the latter. In particular, they have spoken of the little more than 200 lines of resolution provided by VCR, with one letter contrasting this with DVD's 576 lines.

This requires clarification. Both DVD and VCR produce the same vertical resolution. Nominally 625 lines, some of these lines are used during the vertical blanking intervals (during which the electron beam returns from the bottom of the screen to the top). For PAL, the number of displayed lines was traditionally 585. For DVD, 576 lines was settled upon. The difference is insignificant (most displays lose several lines through overscan at both the top and the bottom).

This 580-ish horizontal lines spread over the vertical dimension is the same whether the picture is from VCR, broadcast or DVD (assuming a full screen DVD picture).

The resolution sometimes specified for VCRs is often stated as '200 lines' or maybe a little more. Where does this come from? This is not the vertical resolution at all but the horizontal resolution. Rather than the pixels that have been talked about most commonly with the advent of computers, the resolution of TV pictures was traditionally specified in terms of the number of vertical lines that could be discerned across the width of the display. This is where the '200' comes from.

By contrast, DVD players are typically capable of between 500 and 540. Note that the picture on a PAL DVD is actually encoded as a 720 pixel wide by 576 pixel high image, so hardware DVD players lose around 17% of the horizontal resolution during the conversion from a digital picture to an analog PAL signal.

Stephen Dawson,

Gilmore, ACT.