TC=telecine, which is where a film is converted using a machine which scans each frame and its assembled into a movie, decent quality usually
TS=telesynch, video camera used to film a movie screen, sound sourced from a headphone jack, at best the quality is about like VHS
CAM=video camera with mic used for recording the sound, even worse than TS
dvdrip or dvd screener, direct rip off of a dvd or screener version of a dvd, if done properly it can be very very good using xvid codec and come in at 700mb per 2hrs of film
vhs rip, vhs screener converted to digital using a TV card or mpeg encoder, about the same qulaity as a TS usually, maybe a little better due to no problems with alignment issues
vcd format=352x240 mpeg1 with mpeg1 audio, not even as good as a decent vhs, but watchable
svcd= 480x480 @ up to 2mb/sec bitrate, not bad but not nearly as good as a dvd
dvd= 720x480 @ up to 6mb/sec bitrate
hddvd or hdtv 1920x1080 or 1280x720, best quality and is usually mpeg2,wmv, or mpeg4 formats........you wont find much available at this resolution yet, nobody offers it at full resolution commercially yet, even hdtv is still castrated these days
best qulaity codecs are mpeg4 and xvid as far as bitrate vs picture quality, but they have to be done properly
why does the quality vary so much?Cause most people are clueless when it comes to ripping video, it has lots of options and variables, its an art form as much as a science.........someone who really knows how to do it, can make a 4gig dvd video look great even shrunk down to 700-900mb using xvid or mpeg4 codecs
windows software is also notoriously bad at replaying video, doesnt do a very good job at color reproduction or decoding, it has gotten better but if you want the best possible, use linux or OS X, although winXP is leaps and bounds ahead of win98 in this area
one of the best players you will find is media player classic or mplayer if your gonna use windows, mplayer is open source and written for linux but there are versions compiled using cygwin so it will run on windows giving you most of the functions and quality it offers under linux.........make windows media player 9 and 10 look stupid in comparison