Karbosguide.com - Module 7d4.

The MP3s are dynamite


The contents:

  • Introduction to MP3s
  • Psychoacustic algorithms
  • Ripping
  • Links
  • Next page
  • Previous page


  • Introduction

    Since 1998 the MP3 standard has become more and more important, and an enormous success. The potential is even bigger - personally I believe, that MP3 end up being as popular as the Compact Cassette did in the 20th century.

    MP3 is a system to give a huge compression of digital sound files. The compression is lossy (i.e. musical details are cut away). Yet MP3 delivers a sound quality (almost) as good as uncompressed CDs, due to the very intelligent psycho-acustic algorithm reducing the file size.

    The MP3 format is very versatile; it can be hosted on any storage media and can be transferred on demand over the Internet. You use a ripper to encode MP3 files. These files can be played using a player like Winamp, MusicMatch or Windows Media Player. The MP3 files can also be decoded an used for CD-recording:

    German research

    MP3 means MPEG Audio Layer 3. It is an audio compression technology being a part of the MPEG-1 and MPEG-2 specifications. MP3 compresses CD quality sound by a factor of 8-12, while maintaining almost the same high-fidelity sound quality.

    MP3 is developed by a German research institute called Frauenhofer. The company Thomson Multimedia has patented MP3 in USA and in Germany.

    Effective compressions

    Music on CDs have a bandwidth of 1.4 Megabit per second. It is calculated as 2 X 16 X 44100 bit/sec. This mean that one minute of music on a CD takes up 10 MB of data.

    Using MP3 this bitstream is dramatically reduced (by factor 8 to 12). A typically MP3 file will need 128 per second. Hence one minute of music is reduced from 10 MB data to only 1 MB. Greater compression ratios are also possible for use on Internet etc. but here you will encounter a decrease in sound quality.

    Standard MP3s hold approx. 1 minutes hi-fi music per megabyte.

    This reduction is only possible using a set of compressions.


    Lossy compression with psychoacustic algorithms

    Overall we have to types of compression:

  • Compression without loss
  • Lossy compression

    If we want compression without loss, we use systems like ZIP. This is very effective compression data files that hold plenty of redundant information. This could be Microsoft Word documents, they often zip very well. And when you unzip them, the document is identical to the original. You find similar compression within GIF and PNG graphics files, which compress many graphic images very well (but not photos).

    However you do not find much redundant information in music files. A zip compression of raw music data (WAV files) may only yield 10% reduction in file size. Therefore we use a lossy encoding to reduce the music files sizes.

    Lossy encoding mean that we take away music information (just as JPEG encoding take away image information from a photo). The goal is to remove music details you would not hear anyway!

    Since MP3 offers variable compression you will find that the more you compress the music, more details are removed and lesser fidelity is the result.

    Many ways to MP3

    The MP3 standard tells what design a MP3 file should have. It does not tell how to produce the file. This indicates that we may experience quite different quality from different encoders.

    The most important principle in MP3 compression is the psychoacustic selection of sound signals to cut away. Those signals, we are unable to hear are removed. These include weaker sounds that are present but are not heard because they are drowned out (masked) by louder instruments/sounds.

    Many encoders use the fact that the human ear is most sensitive to midrange sound frequencies (1 to 4 KHz). Hence sound data within this range is left unchanged.

    An other compression used is to reduce the stereo signal into mono, when the sound waves are so deep, that the human ear cannot register the direction. Also the contents of common information in the two stereo channels is compressed.

    The Huffman algorithm reduces the file size by optimizing the data code for the most often used signals. This is a lossless compression working within the MP3 system.


    Pirating or legal

    All over the Internet you find pirate copies of commercial music. This is not very good since it is illegal and may stop the development of the technology. At www.mp3.com you only find legal music, but there is lots of it!

    Napster

    A great online music community was created around downloading and sharing MP3 files. This was Napster, and it was illegal. You cannot give away copies of your MP3s to anyone, unfortunately.

    Napster had to close down several times in 2000 and 2001 due to law suits from the music industry.

    SDMI

    Secure Digital Music Initiative. This standard was developed by Sony, EMI, and three other big companies.

    It is a security certification which can be used on MP3 files and other formats. It should help to prevent illegal copies of music. With SDMI a MP3 file can, as an example, be designed so it only can be copied three times.

    SDMI is to built into MP3-players as Rio and MP3-man. Here it verifies the SDMI-sigature on MP3 files. However, the system allows replay of "illegal" MP3s as well.


    The RIO player

    In October 1998 the American organization RIAA (Recording Industry Association of America) tried to stop Diamond Multimedia from selling this great little thing. It is a MP3Man, just like a portable CD player:

    Holding the music in 32 MB of flash memory the player has no moving parts. Without moving parts, it could play for about 15 hours on a single alkaline AA battery.

    The RIO was a revolutionary new device. Later MP3 decoders have come in many (better) versions, including mobile phones and digital cameras as well...

    Karbo's Player

    My own favorite device would be a Sony MiniDisc recorder holding MP3 playback software and an interface to the PC. With the 140 MB MiniDisc you will have a great medium for musical storage. Of course Sony has to protect their music division, but the MiniDisc could be so good in this setup.

    The Minidisc uses it's own compression algorithms much similar to MP3, but in my setup you would be able to copy the already-encoded MP3 files directly to the Minidisc.

    The device should also connect to my HIFI stereo set as well as to the cars sound system.


    Winamp

    I use the little program called Winamp and replay from harddisk through my PC's loudspeakers:

    Microsoft's Windows Media Player also plays MP3s. But It is not as smart as Winamp is.

    Microsoft tried to "kill" the MP3 format introducing their own Windows Media Audio (WMA) format, which is similar to MP3 but not compatible. This attempt to incorporate yet another "digital area" in Windows has failed - not many people prefer WMA to MP3, and this pleases me. Microsoft produces great software, but they should not monopolize everything.

    A good player should be able to produce playlists. A playlist is a little text file, which lists a sequence of songs that are to be played continously. The playlist is a file with the extension M3U. It can be edited using Notepad etc.


    Ripping

    To produce MP3s you use a ripper. You load a music CD into the CDROM drive. The software finds a CDDB database on the Internet and finds the artist name and the title of the disk and each song.

    You just tell the ripper which tracks to rip, and the recording starts. I use MusicMatch:

    I used to rip at a constant bit rate (CBR) 128 kbs, which worked fine. Experts tell me that I should use a variabel bit rate (VBR) setting of 75%. It should produce the best sound quality, using many bits when the music is complex and fewer when it is simple. Here you see the MusicMatch settings for ripping:

    The MP3 format is extremely easy to use. Considering the explosive developments within Internet and electronics in general, MP3 must hold a revolutionary potential capable of transforming the music industry quite a lot.

    We use MP3 for backup storage of our music. When we need a copy of a CD, we "burn" it from MP3's. Here we use Adaptec Easy CD Creator, which works fine:


    MP3pro

    In 2001 a new and updated version of the MP3 standard was introduced. Using better compression, it should deliver same sound quality from files half the size.


    Here you see my DVD-player which plays CD-ROMs filled with MP3 files:


    Links

    Get a MP3 player

    You will have to find the MP3s yourself - start with www.mp3.com

    Get a ripper from MusicMatch

    Microsoft's new player " Windows Media Player " also plays MP3s.


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