PC Hardware A Beginner’s Guide

(^552) PC Hardware: A Beginner’s Guide
MIDI files, which have the file extension MID, are not actually audio files but contain
MIDI data. MIDI can be thought of as a language, a standard for sharing information
about musical events such as the pitch and duration of a note between multiple devices.
How a PC handles MIDI files is dependent upon the system’s configuration. Often MIDI
files are routed to the sound card’s onboard synthesizer, which in turn generates the cor-
responding sounds. MIDI files can also be played back on an external device attached to
the sound card’s game/MIDI port. Windows Media Player will launch MIDI files, but
dedicated MIDI sequencing software is required to create and edit MIDI music.
MPEG
MPEG audio uses a similar compression technique to that used for MPEG (Moving Pic-
tures Experts Group) graphic images (covered a little later in the chapter). It compresses
CD-quality sound by as much as a 12 to 1 ratio and produces reasonable sound quality. The
MPEG audio standard has three layers (Layers I, II, or III) that increase in complexity and
sound quality as the layer number increases. Currently, only Layers I and II are commonly
used. Because of its size and quality, the MPEG audio format, in the form of MP2 and MP3
(MPEG Layer 2 and 3, respectively) is gaining popularity on the Internet and Web.
Sound file formats that use compression techniques (like MPEG) are emerging to help
producers reduce audio file sizes. Most of the compression techniques employed use
what is called lossy compression.Lossy means that in the compression process, part of
the original sound is lost and the reproduced sound will not sound exactly like the origi-
nal sound. Some compression techniques have attempted to improve this situation by
eliminating only the sounds that are beyond human hearing ranges.
MP3 Audio compression is a means of reducing the size of WAV files to make them
more portable and to take up less storage space. MP3 compression has become popular in
recent years because file sizes can be reduced dramatically while retaining most of the orig-
inal WAV file’s audio quality. For example, a 50MB WAV file stored at 44.1 kHz and 16 bits
can be reduced to around 5MB and maintain a sound quality comparable to that of a CD.
Less compression results in larger file sizes but also higher sound quality. The portability
of MP3 has led to an explosion of music trading on the Internet and has caused consider-
able controversy surrounding the potential for copyright infringement.
MP3 files require specialized software for playback, and a number of free MP3 applica-
tions are available on the Internet. Nullsoft’s Winamp is one of the most popular of these
applications. MP3 files are also sometimes available as streaming content on Internet sites,
meaning that the file need not be copied to the local system before it can be played.
Streaming audio is commonly handled by Web browser plug-ins.
MP2 MPEG-1 Layer 2 is an earlier MPEG compression format that produces lower qual-
ity results than MP3; MP2 files can be played back with any MP3 player.
AAC The MPEG compression standard expected to succeed MP3, AAC (Advanced Au-
dio Coding) is another name for MPEG-2, not to be confused with MP2.