Originally posted by: MeBeJediSome of the first-generation players didn't do a very good job of 'downconverting' the anamorphic image for standard TVs. A lot of shimmering was created. This happened because when a player downconverts an image, it (basically) removes one line of resolution for every four. Different players do this in different ways, but generally the older players didn't do near as nice a job as today's do. I don't disagree with that at all -- but I see the word "basically" in parentheses there, implying that a more complicated (and accurate) answer is beyond the scope of this document. "Basically" four lines are being converted to three -- that's incontrovertible -- but how that is done is unclear. I would submit that a picture with one of every four lines of information removed wholesale would be immediately recognizable as such, and virtually unwatchable.
On a 4:3 TV without doing the 'squeeze', the DVD player must be set to '4:3' within its setup menu. This forces the player to 'downconvert' the anamorphic image by removing some of the scan lines. This plays the image back at the correct proportion, but obviously loses some of the original resolution. It can also introduce unwanted artifacts, especially on scrolling credits etc.
Again, this citation is accurate in saying that scan lines are removed, and that some of the original resolution is lost. What it does not say (although having seen other similar references, it seems to imply) is that one of every four lines is actually plucked out whole. It is true that for every four DVD scan lines, three 4:3 TV lines are displayed. It's still not clear that that is done by tossing whole lines away.
When it comes to DVDs, anamorphic DVDs are specially encoded to include more visual information than standard DVDs. When an anamorphic DVD is played on a standard 4:3 TV, every fourth line of this extra resolution is ignored. (Keep in mind that your DVD player needs to be set for a 4:3 TV.) You still get a superb picture and you probably would not be able to tell the difference between anamorphic and non-anamorphic DVDs.
You've quoted too much! A fact I will now use against you: I simply reject any statement like this written by someone who asserts, "you probably would not be able to tell the difference between anamorphic and non-anamorphic DVDs". Fact is, I could write a widescreen DVD page and say anything I liked, but it wouldn't make it true. A half-truth, oft repeated, is still not fact.
If this "toss one of four lines" scenario is true, how come there's never been any explanation of exactly
which lines are discarded? Do you start at the top and go, "keep, keep, keep, toss; keep, keep, keep, toss...," or do you try to keep lines with different information than their nearest neighbours (and therefore preserve detail, but introduce local distortion), or do you do something else as yet unexplained? Doing something like this would be nearly analogous to IVTC, yet there's never been any technical discussion like there has been with IVTC. I submit that this is because it doesn't happen that way; it happens like a Photoshop linear (or bilinear, or bicubic, or Lanczos, or what-have-you) resize.
QED, you cannot "squeeze" a picture larger than 720x480 into a DVD frame. 
