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M P 3

M P 3. What is MP3?. A means of compressing digital sound files which, at CD quality, require some nine megabytes per minute.

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M P 3

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  1. M P 3

  2. What is MP3? • A means of compressing digital sound files which, at CD quality, require some nine megabytes per minute. • MP3 applies existing knowledge, about how the human ear and brain process auditory information, to achieve huge reductions in file size (factors of 10 to 14) with only small reductions in discernible sound quality.

  3. Digital Sound on CD • Audio CDs are made by sampling the wave of an analog sound signal some 16 times a second. • Using right angled steps between the sampling points, the wave is represented in saw-tooth form. Sine/cosine readings from the resulting triangles are expressed in binary code to give high fidelity digital representation of the wave. At play back, the wave is rebuilt from these digital “blueprints”.

  4. Digital Sound and MP3 • The process just described gives top quality sound, but uses around 1.4 million bits per second. This is taxing on secondary storage, and even more so on bandwidth, the major obstacle to a truly multi-media internet. • Moving Pictures Experts Group(MPEG) has devised a set of compression formats for sound and video. MP3 is the most powerful format for audio, using algorithms that eliminate data about sound we don’t usually perceive anyway.

  5. Using MP3 Files • Play them on any PC with speakers, and a sound card plugged into an expansion slot on the motherboard. • Decompress them and record to CD. • For playback away from the computer, buy a portable MP3 player: smaller, lighter, less prone to shock than walkmans; and fewer moving parts to go wrong. • Use the internet to share them with others. (Yes, there are legal implications – more on this later.)

  6. MP3 Players • Unfortunately the term, MP3 Player, is used to denote two very different things: • Software that enables MP3 files to be played on the computer. • Portable hardware devices, like walkmans, that enable MP3 files to be played away from the computer

  7. MP3 Players (Software) • Most of the programs currently available can be downloaded for free from the web, though there’s often a charge for enhanced versions. Check these out: • Winamp from Nullsoft • RealJukeboxBasic from FileWorld. This also includes ripper software. More on this later.

  8. MP3 Players (Hardware) • By downloading MP3 files from PC to player hardware you can listen to them in remote locations. There’s a lot of choice now, and you can spend less than £100 or well over £300. • The market is changing constantly but limits on bandwidth and storage mean MP3 is likely to be around for quite a while yet. Before buying, check out thoroughly. Some of the most important factors are ….

  9. Buying an MP3 Portable • Memory - most come with 32 or 64 MB as standard. This will allow an hour or two of listening. Check out upgradability, and its cost. (Some players have hard disks – from 300MB to 2 GB at time of writing - allowing days of play back time.) • Connection Port - if your PC has USB (Universal Serial Bus) go for a USB player. Transferring from PC to player via the parallel port is much slower. • Software – is ripper software (see later) included? Can the player handle other compression formats, such as WMA? • Other Factors – much the same as for portable CD or cassette players: eg size, weight, battery type, style.

  10. From CD to MP3 • It’s simple to download software like RealJukebox from the web to play MP3 files on your PC (though how you come by them may raise big legal questions). And it’s easy to transfer them from PC to an MP3 player. • But what if you want to create your own MP3 files? This is a two step process that involves ripping and encoding.

  11. Ripping and Encoding • Ripping is the process of extracting audio tracks from CDs and saving them as wave (.wav) files to your hard drive. • Encoding compresses them to MP3 format. You have some choice over how tight the squeeze. The standard is 128 kbps (few can distinguish the results from CD quality), with 96 kbps acceptable to most. At 64 kbps the quality drops markedly, so use only when disk space is at a premium • Thefreebie, RealJukebox, rips and encodes.

  12. Websites • Howstuffworks for a fair overview of the technology: • http://www.howstuffworks.com/ • For practical help try these: • http://search.pcworld.com/query.html?qt=MP3&col=pcw&inthe=63072000&rp=0&dt=in&ws=0&qm=0&st=1&nh=10&oq=&rq=0&dt=in&si=0 • http://help.mp3.com/help/ • This is the most comprehensive site I have seen, covering legal, ethical, commercial issues as well as the practicalities of getting into MP3: • http://hotwired.lycos.com/webmonkey/00/31/index3a.html?tw=frontdoor

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