Get totally free music and movies. Download P2P
software and start file sharing.
Click here No scams, no BS. Get BitTorrent, eMule, LimeWire or
Shareaza
Click here
MP2, MP3 and the Internet
In October 1993, MP2 (MPEG-1 Audio Layer 2) files appeared on the
Internet and were often played back using the Xing MPEG Audio Player,
and later in a program for Unix by Tobias Bading called MAPlay, which
was initially released on February 22nd, 1994 (MAPlay was also ported
to Microsoft Windows).
Initially the only encoder available for MP2 production was the Xing
Encoder, accompanied by the program CDDA2WAV, a CD ripper that
transforms CD audio tracks to Waveform Audio Files.
The Internet Underground Music Archive (IUMA) is generally recognized
as the start of the on-line music revolution. IUMA was the Internet's
first high-fidelity music web site, hosting thousands of authorized
MP2 recordings before MP3 or the web was popularized.
In the first half of 1995 through the late 1990s, MP3 files began
flourishing on the Internet. MP3 popularity was mostly due to, and
interchangeable with, the successes of companies and software packages
like Nullsoft's Winamp (released in 1997), mpg123, and Napster
(released in 1999). Those programs made it very easy for the average
user to playback, create, share, and collect MP3s.
Controversies regarding peer-to-peer file sharing of MP3 files have
spread widely in recent years ? largely because high compression
enables sharing of files that would otherwise be too large and
cumbersome to share. Due to the vastly increased spread of MP3s
through the Internet some major record labels reacted by filing a
lawsuit against Napster to protect their copyrights (see also
intellectual property).
Commercial online music distribution services (like the iTunes Music
Store) usually prefer other/proprietary music file formats that
support Digital Rights Management (DRM) to control and restrict the
use of digital music. The use of formats that support DRM is in an
attempt to prevent copyright infringement of copyright protected
materials, but methods exist to defeat most protection schemes. These
methods can be exploited by the computer-savvy to produce unlocked
files that can be freely copied. A notable exception is the Microsoft
Windows Media Audio 10 format, which has not yet been cracked. This
type of audio file can only be pirated by recording the audio stream
as it is played. If a compressed audio file is the desired result,
this recorded audio stream has to be recompressed and suffers a loss
in quality.
MP3 File Structure
Breakdown of an MP3 File's StructureAn MP3 file is made up of multiple
MP3 frames which consist of the MP3 header and the MP3 data. Frames
are independent items: you can cut the frames from a file and an MP3
player would be able to play it. The MP3 data is the actual audio
payload. In the diagram you can see that the MP3 header consists of a
sync word which is used to identify the beginning of a valid frame,
this is followed by a bit indicating that this is the MPEG standard
and two bits that indicate that layer 3 is being used, hence MPEG-1
Audio Layer 3 or MP3. After this the values will differ depending on
the MP3 file. The range of values for each section of the header along
with the specification of the header is defined by ISO/IEC 11172-3.
Most MP3 files today contain ID3 metadata which prepends the start of
the MP3 frames, this is also shown in the diagram.
Quality of MP3 audio
Because MP3 is a lossy format, it is able to provide a number of
different options for its "bit rate"?that is, the number of bits of
encoded data that are used to represent each second of audio.
Typically rates chosen are between 128 and 320 kilobit per second. By
contrast, uncompressed audio as stored on a compact disc has a bit
rate of 1411.2 kbit/s (16 bits/sample נ44100 samples/second נ2
channels).
MP3 files encoded with a lower bit rate will generally play back at a
lower quality. With too low a bit rate, "compression artifacts" (i.e.,
sounds that were not present in the original recording) may appear in
the reproduction. A good demonstration of compression artifacts is
provided by the sound of applause: it is hard to compress because of
its randomness and sharp attacks, therefore the failings of the
encoder are more obvious, and are audible as ringing or pre-echo.
As well as the bit rate of the encoded file, the quality of MP3 files
depends on the quality of the encoder and the difficulty of the signal
being encoded. For average signals with good encoders, some listeners
accept the MP3 bit rate of 128 kbit/s and the CD sampling rate of 44.1
kHz as near enough to compact disc quality for them, providing a
compression ratio of approximately 11:1. MP3s properly compressed at
this ratio can achieve sound quality superior to that of FM radio and
cassette tape[citation needed], primarily due to the limited
bandwidth, SNR, and other limitations of these analog media. However,
listening tests show that with a bit of practice many listeners can
reliably distinguish 128 kbit/s MP3s from CD originals[citation
needed]; in many cases reaching the point where they consider the MP3
audio to be of unacceptably low quality. Yet other listeners, and the
same listeners in other environments (such as in a noisy moving
vehicle or at a party) will consider the quality acceptable.
Obviously, imperfections in an MP3 encode will be much less apparent
on low-end computer speakers than on a good stereo system connected to
a computer or -- especially -- using high-quality headphones.
