PAL and NTSC on DVDs

[Keith Henderson]

J.C. wrote...

> >> anyway, the PAL thing only applies to videos, not
> dvd's doesn't it?
> 
> No, it applies to DVDs as well.
> 
> This is a subject with a lot of piece-parts, and I'm
> sure I do not understand
> it fully, but here's a summary. Corrections and/or
> pointers to a better article welcome.

I'm just a layperson on this subject as well, but my understanding is that the difference in all "video" (ie, scanned images displayed on rows of pixels on a screen) between No.Amer./Japan (NTSC) and Europe/rest of world (PAL) reflects very basic differences that cannot be changed with any new format.  Conversion is the only way.  And that basic difference is in part due to the difference in electrical power, *not* the voltage difference but rather the frequency, 50 Hz vs. 60 Hz.  Because the scan rate is set to match the frequency of the alternating current in order to avoid weird interference patterns on your screen.

Actually, it is effectively half the frequency (25 vs. 30 scans per second) because the rows of pixels are offset between one (odd-numbered) row and the next (even-numbered) row below it.  I mean, the pixel dots are not in vertical rows, but are 'close-packed' to increase the density.  (Therefore, if your eyes were really good, the top and bottom edge of a screen should look 'sharp' and the left and right side of the image a bit fuzzy.)  And so the image has to be built in two 'halves' (odd and even rows separately, one after the other) in fact.  And so converters (called CODECs? or something) have to 'interpolate' the extra 5 images per second if going one way, and remove some going the other way (NTSC-PAL).

There is also a difference in the pixel density, PAL has (IIRC) higher resolution and therefore more pixel lines per scan (ie., the physical screen is different).  But while that could theoretically be standardized worldwide, the electrical power difference would still remain, and there would still be a need for multiple video systems.  Right?

> Nearly all TVs will only "do" one format. The
> capabilities of DVD players seem to
> vary greatly around the world.

As should be clear, ALL TVs can ONLY do one format (the pixel rows are physical entities), for sure...if they show an image from another format, it is because it has been converted somewhere.  DVD players don't actually show the image, they just read the data off the disc and feed it to the video display device, so that's a fundamental difference there.  And yes, they can have converters (or not) too.  Of course, DVD players more commonly, because it is relatively common to buy a US DVD in a European store, whereas watching TV anywhere, you just project the video that you receive (over the air, or by cable, or from your DVD player), which is normally the right format for your screen (although satellite receivers must have converters in those boxes?, for foreign channels at least).  Less of a reason to have one in your TV then.

> It turns out that
> up-converting NTSC to PAL is
> so easy that most DVD players in the UK include this
> feature. Going the other way is
> harder (I don't know why) or perhaps just rarer.

Maybe it is because NTSC has extra images (5 more) per second that can just be thrown out (or rather, a half-image of the odd-row of Image No. 3-NTSC mixed with a half-image of the even-row of Image No. 4-NTSC to make Image No. 3-PAL, whereas 1,2,5 and 6 NTSC are all taken straight across as images 1,2,4, and 5 PAL.  Repeat until 25 images are made from the original 30.)  ...is the way I think it actually goes.  This happens five times a second, so your eye wouldn't actually see this overlapping of half-images, unless Jerry Bruckheimer was director and the images only routinely last 0.2 seconds between cuts.

> Some players come with their region code set to zero, and
> others can be 'hacked'
> to set this. See e.g. http://www.videohelp.com/dvdhacks

Yes, but some 'hacks' *only* do the region-encoding part (Which is useless if your TV is the wrong type), as some DVD players actually do not have the format CODEC in there.  But many actually *do,* because lots of basic computer-chip parts of DVD players are so mass-produced, that the same basic part is used for 100 different DVD players (of different sophistication and cost).  And the manufacturers just have the extra features either turned 'on' or 'off' via these 'hack codes' to fit the particular model.  I know, that sounds like companies are ripping you off, by selling you a cheap model that can theoretically do exactly what the more expensive one can do, even though all the same electronics are in there.  But I gather it is not so simple as that...and I have heard that using a hack code to turn on a feature is sometimes dangerous to your player, because it is enabling a feature that the *rest* of the electronics in the device is actually not
 designed to cooperate with.
 
> There is no PAL/SECAM/NTSC stuff with Blu-Ray disks, but
> there are region codes still.
> So far most disks seem to be region-free. Also note that
> the regions are different
> from DVD region codes (there are only three of them, for
> example).

I don't know anything about BluRay, but this must be true only if BluRay is a completely new video system.  Which I guess might be true, because it is SuperHighDef (right?), with presumably many more pixel lines per image.  So if you project it on any standard TV of today, the image at that point would then be downgraded/converted to either PAL or NTSC.  But if it were on a super duper plasma high-def TV, then it wouldn't.  So the (TV) display and the (disc) output are not necessarily one and the same, no matter the situation.  And if BluRay is a totally new video format of its own, wouldn't its scanrate(s) still have to be set to fit the electrical power grid?  Or is there something so fundamentally different about HD that that isn't an issue anymore?

Grakkl, who took a course in digital video editing a few years ago, but has unfortunately no practical experience in the field