kaiyen's Trading Glossary
2) Analog is a direct, physical representation of a wave form. Because of this, it is possible to go slightly over 0db while recording in analog - it'll sound more dynamic, in fact, if you go a little over. the downside is that the accuracy of this representation is dependent on the medium upon which it is recorded. That is why something like a Maxell XL2 is better than some cheap tape - the Maxell tape formulation works better at capturing the wave form accurately.
B&P or B+P
Blanks and Postage. Basically, you send blanks to a trader, along with return
postage, and they spin a show for you. The trader gets nothing, technically,
in return. Except, hopefully, your gratitude.
Balanced Connections
Balanced Connections utilize a postive, negative, and ground arrangement.
The presence of the ground signal allows the output to be compared against the
ground in order for any noise that was picked up during the cable run to be
removed. Balanced connections are almost always on XLR connectors.
CDR or CD-R
Stands for "CD-Recordable." A compact disc that you can record once to.
Can store up to 650 mb of data or 74 minutes of audio. In order to play in an
audio player, the session must be closed.
CDR's have a lower reflectivity than commercial CD's - about 70%. While most newer audio players, even cheap discman units, can read them fine, there are some older transports that can't handle the lower reflectivity.
CDRW or CD-RW
Stands for "CD-ReWritable." A compact disc that you can write to, erase,
then rewrite to. Stores up to 650 mb or 74 minutes of audio. Only about
20% the reflectivity of a commercial CD, so very few audio players can
read them. You need a multi-session CD-ROM drive to read them on your
computer.
Coaxial
Sometimes abbreviated "coax." It means there are two electrical signals
on one cable - one on the inside, one on the outside. This is one format
through which digital audio is transmitted.
Consumer CDR
A $5 CDR. It's a slightly different formulation designed to be particularly
friendly to audio players (for instance - the TDK one is supposed to play in
every cd player, guaranteed). It's also supposed to be handle the digital copyrighting,
SCMS, better than a regular CDR, though I don't know how. It costs more. Used
in consumer standalone CDR's.
DAE
Digital Audio Extraction. When you want to pull audio data
off a CD, you want to keep it all digital, right? You need to "extract" it from
a CD-reader drive (CD-ROM or CDR). Not all readers can do DAE, and most cannot
to it with any sustained degree of accuracy. Plextor drives are an exception,
since they have built-in jitter correction for more accurate extraction.
DAO
Disc At Once. When you burn a CD Disc-At-Once, the
laser never turns off and it's written as one continuous stream of data.
It also closes the disc so you can't write to it anymore. The benefit of
this to trading CD's is that you eliminate the 2 second gap between tracks
that other methods, like Track-At-Once, produce. Never accept a CD not
burned DAO.
DAT
Digital Audio Tape. It's a digital, tape-based magnetic
medium. DAT tapes are smaller than analog cassettes and playable only in DAT
players. They are used on the taping scene in 60m (2 hour) or 90m (3 hour) lengths
commonly, and use sampling rates of 32, 44.1, or 48KHz.
Dither
Dither is a process through which exta bits in the digital audio stream
are removed. Usually, it happens when there is a 20 or 24 bit converter going
into a 16 bit device (like an SBM into a dat deck). Obviously, the extra bits
have to go away, and there are different ways of doing it. Many devices merely
throw away the least significant bits, while others, such as Sony's Super Bit-Mapping,
actually does sound analysis and shaping to produce the best possible dithering
result.
Jitter
Jitter occurs when digital audio loses sync. Along with the actual audio data,
digital audio signals (either S/PDIF or AES/EBU) carry a synchronization bit
that keeps all the devices attached to that audio signal on the same clock.
However, poor connections, either from just poor circumstances or too many machines
slaved off the main digital output (e.g. - patchers in a chain at a show), can
cause jitter to occur as the sync is lost. This causes errors in the datastream,
which is a big problem.
MD5 or MD5sum
MD5's or MD5sums are long alphanumeric strings used to verify some data
set. In terms of trading, MD5's are used to create unique numbers that verify
that a Shortened audio file is intact and accurate. It is very important to
utilize MD5's to make sure the downloaded files are complete.
Minidisc
Minidisc is a relatively new digital media, out for about 8 years now. It is
a 2.5" square rewritable disc in a cartridge, so it's smaller than a CD, allows
you to write to it many times over, and is better protected from scratches and
whatnot. It holds 74 minutes of audio, the same as a CDR, by way of a dynamic,
psycho-acoustic compression algorithm called ATRAC. ATRAC attempts to determine,
in real-time, what frequencies the human ear should not be able to hear and
eliminates them, making the file small enough to fit on the disc. MD's use a
magneto-optical phase-shift technique to make them re-writable - similar to
CDRW.
MKW
MKW is a lossless compression format created by Michael K. Weiss, the developer
of the MKW Audio Compression Tool. It was developed almost concurrently with
Shorten but is slightly less efficient, and therefore not recommended nor intended
as a replacement to SHN.
MP3
MP3, or MPEG 1 Layer 3, is a compressed audio format that has become very popular
because of a pretty decent balance of sound quality and file size. Considering
the files can be small enough to be downloaded even by modem-speed connections,
they sound pretty decent. There are people who trade mp3's with others. However,
while mp3 compression is psycho-acoustic, like Minidisc, it does not have a
fixed rate of compression, and you can have wildly varying degrees of accuracy
and sound quality with mp3's. Because of that, and the ease with which mp3's
can be decompressed and burned onto cd's, I am personally not a big fan of mp3
trading. It's fine for what it does - serving as a file format for transfers
(I use them often to "sample" something) - but I avoid them as much as possible.
Rippers
19th century English serial killer...
An Audio Ripper is software that does audio extraction. I strongly recommend that you use a dedicated piece of software for extraction - something like Adaptec's EZ CD Creator does really inaccurate DAE. Though Goldenhawk's CDRWin is pretty good, so I've heard. I use winDAC. These can be found at http://www.mp3.com under the software/rippers link.
Sampling Rate
Sample rate is the rate at which a digital audio device samples the full
analog sound wave. Digital audio is a representation of the full wave - it's
takes a series of "snapshots" of the wave, and the more snapshots
it takes, the more accurate it sounds. The higher the sampling rate, theoretically
the more accurate it sounds. CD Audio and Minidisc are standardized at 44.1KHz,
or 44,100 samples per second, while DAT can do 32, 44.1, and 48KHz. Super Audio
CD, DVD-Audio, and High Resolution DAT can go up to 96KHz.
SCMS
Serial Copyright Management System. It's a copyright
protection system for digital audio. SCMS data is found on CD's, DAT's, MD's,
DCC's - any digital audio format. SCMS can be three settings: 00 (unlimited
copy), 11 (one copy allowed), or 10 (copy prohibited). This applies only to
digital copies, and is usually only heeded with consumer and some semi-pro machines.
Shorten or SHN
Shorten, sometimes abbreviated SHN (the 3 part dos extension), is a loss-less
audio compression program. It is used on distribution systems such as PCP and
DDS.
Soft-Limit
A feature on the Apogee AD-1000 analog-digital converter that is, essentially,
a limited with a relatively slow attack time. This allows the freedom of knowing
that the likelihood of severe clipping is very slim from sudden peaks in levels
while avoiding the brickwall style of limiting found in other units.
S/PDIF
Sony/Phillips Digital Interface Format. It's the most common standard for passing
digital audio. Connections are either electrical or optical, with either coaxial
or toslink connectors, usually.
Super Bit-Mapping
Sony's dithering process used in their SBM-1 unit and many of their dat
decks.
TOSlink
A type of connector used for optical digital connections. Kind of squarish,
with a bit of a tube in the middle for the light to go through. TOSlink connections
use fiber-optics and a rapidly pulsing light to transmit digital data.
Unbalanced Connections
Unbalanced connections are audio connections that only have a postive and
negative side. These connections do not have a "ground" that is used
to remove any noise that may have been picked up during the cable run. Common
unbalanced connections include RCA and 1/8" miniplug.
Word Length
Word length refers to the number of bits utilized in a sample of digital audio.
Keep in mind that digital audio is merely a representation of the original sound
wave - just like the inherenty inability for a computer to draw a curved line,
digital audio takes pieces of the full sound wave - samples, of a specific size
and at a specific rate, to get the best possible representation. Clearly, the
bigger that size and the more often those samples are taken, the more accurate.
The Word Length is the size of each sample - CD Audio, Minidisc and DAT standards
utilize 16-bits, while Super Audio CD, DVD-Audio, and High Resolution DAT can
go up to 24 bit. Many converters will use 20 bit to increase their resolution,
but still dither back down to 16 at the input and output.