Audio CD and DVD formats
Audio CD formats
There are two kinds of CD formats, audio CDs, and data CDs.
There are three kinds of CD media, "pressed" (manufactured
commercially), CD-R (recordable once), and CD-RW (recordable and
erasable many times).
Audio format CDs are used for storage and playback of digitized
audio data, and can be played back by any audio CD player.
The recordable audio CDs you can buy in stores are no
different than the recordable data CDs you can buy in the same
stores for a lower price-- audio format data can be written on
either. The audio CDs include in their price a royalty
payment for musicians, so if you plan to copy commercial music you
should buy them. For non-commercial music, recordable data
CDs are fine.
Most CD players will not only play the "pressed" CDs, but also
music recorded in audio format on CD-Rs, but few will play music
recorded in audio format on CD-RWs. It is possible, but generally
pointless, to create a CD-RW in audio format. Fortunately, you
can erase the CD-RW and make something else with it.
Computers can also play audio CDs, but they are generally capable
of playing audio CDs from any audio format media: "pressed", CD-R,
For computers, a variety of types of audio files have been created
to save space. The standard audio format used on audio CDs is
generally stored on a computer as a .wav file. The .mp3
format is a compressed format that can save lots of space compared
to standard audio .wav files. The compression factor can be
adjusted, but many have found that using a bit-rate setting of
128Kbps (Kilobits per second) is the sweet spot between saving
space and yet still having excellant audio quality. ;Using
that bit-rate setting, .mp3 files are about an order of magnitude
(factor of 10) smaller than the same music in a .wav file, allowing
for 10 times the music per unit of storage or bandwidth.
Microsoft invented a competing format, .wma, which compresses
even better, allowing smaller files than .mp3 for the same quality,
but I prefer open standards supported by many vendors, without the
need to pay royalties to Microsoft, so I stick with .mp3 formats.
There is also the Ogg-Vorbis format, which is an open
standard, but it hasn't yet caught on enough to be a particularly
As a result of the exploding popularity of .mp3 files, some CD
players now support playback of audio data from data format CDs
containing .mp3 files. While this allows a CD to contain ten
hours of music instead of one, some of the standalone and auto
players have stated and unstated restrictions on the number of
files, folders, and depth of folders that can be supported.
Both MP3 CD players that I have state their limits of
folders, and folder depths, and they are generous, yet one of the
players will not play all the songs on one MP3 CD I have, which
meets those limits, and the other will. I can only speculate
that there is an unstated limit on some other measure, perhaps
total number of files, because I do have many files on that CD.
Most computer software used to play MP3 CDs have no such
limits, so when building MP3 CDs one must understand all the limits
of the device. Having only some of the limits specified makes
this a trial-and-error process... rather than displaying a
meaningful error, my player simply plays a subset of the songs on
It also seems that there are variations in the ability of some MP3 players
to accurately play music that has been compressed with some of the standard
compression techniques. What one player will play fine, another will play
but with playback artifacts, that sound like skips in the music, or other
Some auto manufacturers are including MP3 CD players in newer
models; older models can be replaced. Some auto sound systems
(especially newer ones) have line-in jacks so that portable devices
can be connected. There are adapters to connect a variety of
devices to auto cassette decks, or to connect to little FM
transmitters so that the auto radio tuner can tune in to the
Audio DVD formats
There are apparently 3 competing formats for Audio DVDs. Wikipedia has a reasonable description of them all, and points out that:
From a purely technical standpoint, the sound resolution of a DVD-Audio recording (sampled at 24-bit/96 kHz) is substantially better than a standard CD recording (which is sampled at 16-bit/44.1 kHz). However, some people report that they cannot hear a difference between DVD-Audio and CD-Audio. Furthermore, some doubt that the quality difference is large enough to justify purchasing new playback equipment and repurchasing records in DVD-Audio format.
While this was said about DVD-Audio, it appears to apply to all three formats. None of the 3 competing formats really have much of a user base at this point.
The first is called "DVD-Audio". It supports either more music, higher quality music, or more sophisticated multi-channel music. And copy protection.
The second format is called "Dual Disc," and it claims to be playable in "most" CD players, but doesn't conform to the specs of the CD, so may not play correctly in some. The media is thicker than normal CDs, so slot loading players may not work. I'd ignore this format.
The third DVD format, is called "Super Audio CD", and is really based on DVD technology, but is another "Betamax"-like format from Sony, so should be ignored.
Of course, there are also DVD data formats, on which MP3 files may be placed. There are apparently a few DVD players that will play DVD data disks containing MP3 files. You can cram lots of music on a DVD in MP3 format.
Another difficulty is that DVD data formats come in multiple varieties. DVD-R, DVD-RW, DVD+R, and DVD+RW. The latter two, from Sony, should be ignored. There is a new "dual-layer" DVD format also, for even higher capacities.