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Personal computers are better and better and they can work with sound and read CD-ROM discs. They use microchips which are for fast moving in programs. In this way are assumptions for multimedia good.

Multimedia is very used word now in present. Multimedia means using more then one media for presentation of information. It can be simple pictures in a book or difficult computers programs stored sounds, texts and video clips. These applications are today the most useful from all multimedia. Combinations of media on personal computer are very good for fun and knowledge.
Interactive multimedia enables to user direct a way of presentation of information. Connection between information is called hyperlinks interconnection and it is useful for learning programs because user can choose his own procedure when he is working.

CD ROM discs

Maybe the most used method of stored information is CD-ROM discs. Abbreviation CD-ROM means Compact Discs Read Only Memory. It means that information on disc can be only read we can not change them. CD-ROM discs are popular method of presentation. It is because on one can be 650megabyts of information. It is same amount of information which we can save on 503 and half floppy discs.

Principle of CD-ROM discs is as principle of normal audio discs and most CD-ROM mechanisms know play audio discs.
Time which computer needs for finding information on a disc is called access time. Access time of modern computer is about 200ms (mili second). It is 10x more than access time of hard disc. Long access time of CD-ROM discs makes computer needs more time for finding information. However computer technology is still better and access time is still shorter, which is good because when it is short computer do faster our needs.

Computer system usually has CD-ROM mechanism and stereo device with speakers and sound card. Sound card is card which is installing into computer. Card read context of sound sets and play them by speakers or headphones. We can record sounds by microphone or electrical instruments. Computer changes sound waves to digital form and save it on disc. Without sound card can computer makes only simple sounds.

Sound sets

Most sound card knows make and play two types of sound sets – WAVE sets and MIDI sets. Sound is waves which go through air and shake our ear drums. In cochlea are these vibrations changed into signals which brain interpreted as sound. WAVE sets save curve of wave of recording sound.
MIDI sets save instructions which are need for making sound. It can be used only for saving music and contents from information about playing tones.
Next factor on which depends quality of recording sound is number of bits which computer know save. Bit is the smallest unit of information saves in computer. More bits = better record. Sound card are most 32bits. 32bits card can distinguish and record small details too.


MP3. What is it? If you have never heard about MP3 file and wondered what it is or how it works then it will be my pleasure to introduce you „what is a MP3“. Making of MP3 file is based on compressing original music file into the file of smaller size but almost the same quality. Principle of this compression is based on imperfection of human ears, which can’t catch the whole scale of sounds. These are sound which are above or below the scale of tones which can be heard by human (above 20 000 Hertz and below 20 Hertz). The MP3 format is a compression system for music. The MP3 format helps reduce the number of bytes in a song without hurting the quality of the song's sound. The goal of the MP3 format is to compress a CD-quality song without noticeably affecting the CD-quality sound. With MP3, a 32-megabyte song on a CD compresses down to about 3 MB. For example: A size of 4 minute song is normally about 40 megabytes but after compressing it into MP3 file it has only 4 megabytes and the quality is almost about the same. This lets you download a song in minutes rather than hours, and store hundreds of songs on your computer's hard disk without taking up that much space. However, the quality of this compression wasn’t always as good as now. Before MP3s we knew MP1 and MP2 files, although these weren’t used almost at all.

To make a good compression a technique called perceptual noise shaping is used. It is "perceptual" partly because the MP3 format uses characteristics of the human ear to design the compression algorithm. For example:
  • there are certain sounds that the human ear cannot hear.
  • There are certain sounds that the human ear hears much better than others.
  • If there are two sounds playing simultaneously, we hear the louder one but cannot hear the softer one.

Using facts like these, certain parts of a song can be eliminated without significantly hurting the quality of the song for the listener. Compressing the rest of the song with well-known compression techniques shrinks the song considerably. When you are done creating an MP3 file, what you have is a "near CD quality" song. The MP3 version of the song does not sound exactly the same as the original CD song because some of it has been removed, but it's very close. MP3 is so popular because of its small size, but mainly because of a high quality which can be found in few megabytes.


MP3 players

MP3 players are for playing MP3 files on a computer. The most popular are Winamp or Sonique. In the last two years portable MP3 players has been introduced. We can divide them into three groups:

The first one looks like standard Discman with the slight difference. It can read MP3 files from a CD, and because these are smaller size, we can keep about 200 songs on one CD.

  • small prize
  • it can read normal audio CD too


  • big dimensions
  • sometimes problems playing by walking

The second is players with flash memory into which we can record songs straight from computer. The number of songs that we can record to this player depends on size of its disc, but it ranges from 16 songs to 5 000 songs.

Advantages: -it is stored device too
-we can listening a radio or record sounds
Disadvantages: -smaller memory (128 or 256 MB =2-4 hours of data in MP3 format)

Third possible are devices which use hard disc. Capacity of these hard discs is 20-60 GB so we can save on them all our CDs in MP3 format.
Advantages: -big memory
Disadvantages: -big dimensions
-big prize

If you want to have MP3 file you can use one of these two ways:
  • if you have a CD collection and would like to convert songs from your CDs into MP3 files, you can use ripper and encoder software to do just that. A ripper copies the song's file from the CD onto your hard disk. The encoder compresses the song into the MP3 format. By encoding songs, you can play them on your computer or take them with you on your MP3 player.
  • If you have an internet you can download MP3 file from it (but this one is not legal!!!).

If you would like to download and then listen to MP3 files on your computer, then you need:

  • A computer
  • A sound card and speakers for the computer (If your computer has speakers, it has a sound card)
  • An Internet connection
  • An MP3 player (a software application you can download from the Web in 10 minutes)

Knowing about the MP3 format isn't half as interesting as using it. The MP3 movement -- consisting of the MP3 format and the Web's ability to advertise and distribute MP3 files -- has done several things for music:

  • It has made it easy for anyone to distribute music at nearly no cost (or for free).
  • It has made it easy for anyone to find music and access it instantly.
  • It has taught people a great deal about manipulating sound on a computer.

The MP3 movement is one of the most amazing phenomena that the music industry has ever seen. Unlike other movements -- for example, the introduction of the cassette tape or the CD -- the MP3 movement started not with the industry itself but with a huge audience of music lovers on the Internet. The MP3 format for digital music has had, and will continue to have, a huge impact on how people collect, listen to and distribute music.

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