2007 — 17 Mar: My eyes are still bleary

Remember last night's A/V experiment? The little Helios DVD player acquitted itself well. Mike's giant (but slightly venerable) projector TV is a fussy eater, digesting best an analogue progressive PAL signal, ideally presented via a VGA input. (Hen's teeth is a phrase that springs to mind at this point, of course, as in "that's about as rare as...") so we used Mike's tiny Xbox-intended component-to-VGA converter for that trick.

First test:1 The video montage section from Joe Kane's DVD Video Essentials which Mike also has, but in its NTSC variant. Black level, convergence, and colour all looked fine. Time for the second course. We tried it on the NTSC DVD of Star Trek: Insurrection which has a notably difficult opening scene with lots of straw and some pans across a canoe and some tiled roof buildings with nice tricky diagonal edges (all very revealing of imperfect 3:2 video pulldown). No problemo. But this wasn't progressive PAL (which the Helios can certainly output via its component sockets). Third test: its first PAL DVD. At this point (by leaving the Helios set on NTSC 480p output) we discovered what an effective NTSC-to-PAL and PAL-to-NTSC converter2 it is in its own right.

Finally we tried the variety of resolutions available via the "real" VGA socket rather than the component outputs. To see these properly would have involved more time setting up the projection system than would have been strictly polite for what was also supposed to be an evening dinner party so we took off our propellor hats and rejoined the human race.

Television pun department

These two little lads sit atop the loudspeaker that handles my left front channel. Do you like my name3 for the pair? They are, of course, the only type of TV "dogs" I can abide! (The digital ones run the risk of burning themselves onto my plasma screen.)

TV dogs

Right of Reply department

Mine host was kind enough to comment:

Via component, we watched the first two NTSC discs as you said. Then we started on the real VGA socket, and were surprised4 that the "640x480" actually seems to be 480p, as the projector locked onto the signal perfectly.

Then we watched a PAL disc. I can't remember whether we watched it via component or your VGA socket at first, but we tried them both. Via component we were able to get a true 576p signal (with Macrovision), but it was via your VGA socket that things got interesting, and we realised the machine was transcoding the 576i signal from the DVD into "640x480", or 480p as we prefer to call it! And without Macrovision too.

PS. Regarding Macrovision, I think I can explain what the SuperFi site is claiming, and it's true. The only time you get a Macrovision signal out of the Helios is when you don't perform any processing, in which case it outputs the 480i or 576i signal from the disc, along with its Macrovision bursts. This is what you tried to feed into your DVD recorder, and it saw the Macrovision crap and refused to record. However, if you transcode the signal to any other resolution (which is, after all the main purpose of the Helios), then there will be no Macrovision signal on the transcoded output...

Mike Prince

Day 134  


1  Understand this, young Jedi. Setting up an A/V system doesn't have anything to do with sitting down and watching stuff for pleasure. Do not be seduced by the dark side.
2  Back when I was but an innocent youth (round about 1993 or so) I borrowed the Hursley Lab's video studio TV systems converter over a Christmas holiday. This was a then-new piece of kit (a 19" rack-mounted device) that had cost something fairly staggering in the thousand pound plus area (back when a pound was jolly nearly a pound in almost anybody's money, remember). It did a reasonable, but not too exciting, job of conversion between an NTSC LaserDisc I had and a blank PAL tape I wished to copy it on to as an experiment.
3  Winston Churchill, in case you needed telling.
4  Aren't all VGA type signals progressive?