DVDs are not the only "CD" type discs that will play in many current DVD players

the other disks are:
MiniDVD (MPEG2 encoded, a standard CD format of about 15 minutes, equal to DVD quality), simply puts files mastered for DVD on to a standard CD, with obvious restrictions on the length of the material.. they may or may not play on a standalone DVD player...they usually work fine in computers though, being recognised by software DVD players as DVDs - they require PCs or MACs to the spec of the software DVD player. They can be copied by any CD writer too!
Known compatable standalone players:
Afreey LD2060
Cyberhome 528 ( provided bitrate <5Mbps)
most stand alone DVD players will not handle a video bitrate higher than approximately 2.5Mbps ... going higher than that causes stuttering playback because a CD does not spin as fast as a DVD and 2500kbps video with 224kbps audio is about the bitrate limit of the CD format
_________________________________________________
Audio CD 44.1KHz sampled stereo audio uncompressed
_________________________________________________
VCD (VideoCD): MPEG1 encoded, a standard CD format of about 70 minutes of "similar to VHS quality" video and CD quality sound.
"VideoCD" is the most compatible and widespread format, even Sony Playstations can play them (via an adapter).

Most DVD players can play pre-recorded VideoCDs, but some have problems with VideoCDs recorded with a CD Writer onto CD-R or CD-RW (e.g. on a computer). This is due to the different reflectivity of CD-R disks. Newer models with "dual-laser pickup" do not have a problem. Some older models are happier with CD-RWs which are closer optically to DVDs.
VCDs can be played on PCs via appropriate DVD software (see list at bottom of the page). Some software will accept CD players as a substitute "DVD", and treat VCDs as though they were in a DVD player. Alternatively the mpg1 files themselves are in a directory MPEGAV on the CD with names like AVSEQ01.DAT. These can be copied to your hard disk, then rename the extension to mpg (e.g. AVSEQ01.MPG) and the file will play in windows media player, (or any other mpg video player). You can try "right clicking" on AVSEQ01.DAT and select "open with" Windows media player, but it usually objects to the "dat" file extension.
Best players: Zoom divx/dvd player... no problem playing VCDs straight from a CD drive. Zoom is a very versatile, compact and FREE program see download or http://pisho.net or http://www.inmatrix.com version 2.4 at time of writing (feb 2002).
_________________________________________________
SVCD: MPEG2 encoded, a standard CD format of about 40 minutes of "similar to SVHS quality" video, though depending on the original material and encoder it can get very close to DVD.
Fewer standalone DVD players are able to play SVCDs than there are models that play VCDs. However most models made after 2001 should play them.
SVCDs it seems cannot easily be played on PC CD players, despite starting out as an easily playable MPG2 file. During the "make it an SVCD" process the file is enclosed in a "wrapper", which makes it unreadable by Microsoft's Direct Show (part of the software required to play video). As SVCD is not a product used much commercially it's unlikely Microsoft will fix Direct Show in the near future (version 8 doesn't play SVCDs). However if you wish to try, the mpg2 files themselves are in a directory MPEG2 on the CD with names like AVSEQ01.MPG. You can try "right clicking" on AVSEQ01.MPG and select "open with" Windows media player. Later versions of media player will access the Internet to try to download the appropriate plugin. As with VCDs you might try copying to the hard disk and renaming the extension this time to MP2.
_________________________________________________
XVCD (variable length) non-standard format which may or may not play in a standalone DVD player.
_________________________________________________
DivX (90min MPG4) has been made popular by its ability to fit a full feature film on a single CD. standalone DVD players don't play them.

_________________________________________________
MENUs on VCD/SVCD

Putting menus on VCDs usually doesn't affect their playability. If the DVD player doesn't support VCD/SVCD menus, they will still play the video. Exception seems to be software players, Intellivision WinDVD version 2 has been found to hang on a VCD with a menu (and not even play the video).
Menus are fine on PowerDVD (PC version v3), but requires a DVD player rather than a CD player to be installed.

_________________________________________________
Software DVD Players reviews at http://www.inmatrix.com:
ATI DVD Player v4.10 (updated May 15th, 2001).
Software CineMaster 2000 v2.0.37.6379 (updated June 21st, 2000).
CoolDVD v2.1 (updated April 20th, 2001).
DVDExpress v5.0x (updated September 29th, 1999).
Odyssey Player (updated September 16th, 1999).
PowerDVD v3.0.1021 (updated December 4th, 2000).
SoftDVD MAX v6 (updated April 11th, 2001).
VaroDVD 2000 v2.03 (updated August 1st, 2000).
Xing DVD Player v2.03 (updated June 5th, 1999).
Windows 98 DVD Player v1.0.0.1 (updated June 5th, 1999).
WinDVD v3.0
Zoom v2.4 -plays DVD, Divix, VCD, avi, mp1, mp2

Technical & Links:
VCD standard: MPG1 compression 352x288 25 fps (PAL). 44.1KHz stereo audio
SVCD standard: MPG2 compression 480x576 25 fps (PAL). 44.1KHz stereo audio

DVD player compatibility list
a test SVCD (NTSC) file SVCDSample.cif (17Mb) that can be put on a CDR to test your DVD compatibility. You will need a CD writer and Adaptec Easy-CD to cut the disk.
(Full info on www.vcdhelper.com). There doesn't seem to be a test PAL version on the net, so we will put one up soon...