User Guide

AUDIO FUTURA
AUDIO FUTURAAUDIO FUTURA
AUDIO FUTURA S.P.A. April 2010 | revision 1.0
USBDAC Application Note 6 / 7
make itself compatible with iTunes. In fact now Windows Media Audio can convert its file audio from a WMA format to the AAC one
which is the most used in iTunes.
On the 28 April of 2003 Apple Inc. has published on web its iTunes Store which is a on line shop where buying music as a whole CD
or as single track and also many other audio/video files. iTunes Store has imposed itself as the most important on line music shop
with more than 70% of the whole on line music purchases performed on iTunes Store. For selling music on its music-web-shop,
Apple has reached agreements with the main record producers such as: BMG Music, EMI, Sony Music, Universal and Warner Bros.
Moreover agreements are every day reached with the smaller record producers. iTunes let you download a single track at a price
of less than a dollar and require the payment via a credit card on encrypt and absolutely safe web pages.
With iTunes you can create your playlist, which can be then transferred to the iPod. The protection system on the music
downloaded from the iTunes Store is the: Apple Fair Play, a Digital Right Management integrated based on iTunes Store, such
protection System let you burn a unlimited number of copies of the downloaded music while the music can be played by a 5
maximum number of computer .
Glossary
AAC: is a compressed audio format (Advanced Audio Coding) from MPEG and has been included into MPEG-4. At the same
compression is characterized by better performances than the older MP3. Is the most used audio format for iTunes. It is a “lossy”
compression algorithm.
AIFF: (Audio Interchange File Format) is an audio standard used to save audio recordings on a PC. Is not a compressed format. The
AIFF has been designed by Apple Computer developing the “Interchange File Format “ by Electronics Art. The AIFF is commonly
used in the Apple MACs, that’s why is known also as Apple Interchange File Format (AIF).
ALE: Apple Lossless Encoder (known also as Apple Lossless, ALE, or Apple Lossless Audio Codec, ALAC) is a audio Codec by
Apple Computer developed for a lossless compression.
APE: is a audio lossless
compressed format by Monkey’s Audio. By this algorithm the original file is compressed till the 60% with
no lost of the information. At the moment is probably the best lossless codec for its balance in speed and compression.
ASIO: the ASIO drivers are Windows audio drivers. They were at first realized by the Steinberg Media Technologies GmbH to
facilitate the editing and recording of audio files on a PC. The audiophiles have started using such drivers because they bypass the
Windows mixer and guarantee a exact bit to bit transfer (in a transparent mode with no digital elaboration) to the audio board. A
free revision of the ASIO drivers has been developed by Michael Tippach ASIO4ALL (http://www.asio4all.com/), and is supported by
the Audio Analogue USBDACs.
Bitrate: (transfer speed) in informatics and telecommunications “bitrate” means how many data can be passed through a specific
connection in a time unit. The Bit rate is the amount of binary information (bits) which pass in a second. Such value varies for the
compressed audio file such as for the MP3. The general rule is that the more the bitrate is the more the amount of original
information included and the more the quality of the compressed audio. It is usually accepted that a fair good quality for a MP3 file
is obtained with a 128Kbit/second bit rate. Such quality is anyway poor compared to a CD.
CODEC: is a program or a hardware device which codifies and/or de-codifies a digital signal, such as a audio or video one. Usually
the performed operations change the original file format and involve compression/decompression. Therefore a Codec is a program
or a device which perform operation on digital signals such as the compression/decompression algorithms. For example, to play a
MP3 (or FLAC or APE) file, a player must have the proper decompression program that’s say the proper codec.
Compression: is a technique to reduce the amount of bits required to represent a information. We can distinguish two different
compression types: lossy (with a information loss) and lossless (with no information loss). The lossy compressions reach a very high
compression (a high reduction in the number of bits required to represent the information compared to the original ) but at the
expense of a loss of the original information. The lossless compressions can instead reach a smaller compression but the
compressed file when decompressed is indiscernible from the original file. The compression is usually performed to reduce the
memory required to store the file or to transmit the file in a shorter time. Any compression/de-compression is performed by a
dedicated algorithm. In audio there are many compression algorithms both lossless such as: FLAC, APE, ALE and loosy such as
MP3, WMA (windows Media Audio), Vorbis, AAC, MPC.