Good morning. Now I’ll tell about Multimedia.

Multimedia.

Good morning. Now I’ll tell about Multimedia.

In my report I will speak about the main groups of MM files, about different methods of storing, transferring and to compressing data and the algorithms of main compression methods.

The Multimedia is a combination of two or more concurrent (параллельно) communication Medias, such as text, image, sound and video.

One of the key features of Multimedia file is its interactivity. This means, that they can be controlled by the human involvement, for example, mouse manipulation. MM files can be stored in a different ways. They can be stored on a PC’s hard disk, or on a CR- or DVD-ROM, or on some flash memory drives, for example, USB flash drives, Memory stick cards. Files can be archived by some programs, for example Win Zip or WinRar. Archived files require much less space on the hard drives.

All types of MM files are digitized in order to make data transmission simpler and faster. There are different types of transmission of MM files: they can be transferred by the Internet, or by using some kind of memory cards, that make the idea of data transferring simpler and safer. If you want to copy some MM file, you shouldn’t worry about the loss of quality after the copying. If you copy the MM file without saving it to a different format, this operation will be lossless.

There are two main questions connected with MM: the reduction in amount of space, needed to store MM files on hard drives, and saving the quality of MM files after compression. Compression is the reduction in size of data in order to safe space or transmission time. So there are different formats, different types of compression for each communication media.

Text is the oldest and the simplest communication Media. The idea of compression of the text files is very simple. First of all, we have to calculate the repetition rate of some letter combinations, and then encode the combinations with the highest repetition rate with the shortest combinations of bits, and the combinations with the lowest frequency – with the longest combinations of bits. I think, that the idea of text compression is not very important, because usually all text files are rather small and don’t need much space for storage and transmission.

Sound and video files allow us to store the past. That means that we can store the best moments of our life not only in our unreliable (ненадежный) memory, but also on different hard drives. So, in order to recall something we just have to input a CD with the needed information in a CD-ROM drive and watch the past moments of our life and go through them once again.

In order to store sound files, for example music, there were invented many audio formats. The most popular format is an MP3 that stands for MPEG Audio Layer 3. MP3 competes with another audio file format, called WAV. The key difference is that MP3 files are much smaller than WAV files. An MP3 file can store a minute of sound per megabyte, while a WAV file needs 11 or 12 Mb to hold the same amount. The idea of MP3 compression is that MP3 significantly (существенно) reduces the stored information by stripping out sounds most people can’t hear. For example, most people can’t hear notes above (выше) the frequency of 16 kHz, so it eliminates them from the mix. An MP3 file can also provide some information about itself in a coded block called a tag that can include the performance name, a graphics, the song lyrics and etc. There are many programs that were developed to make work with compressed files simpler.

A ripper is a program that rips songs from a CD in your CD-ROM drive and turns them into WAV files. An encoder converts WAV files or vice versa (наоборот). Many MP3 players, such as Windows Media Player, incorporate (включать) rippers and encoders and can do both steps in one. In MP3 format files can be compressed up to 12 times.

MIDI was developed as a standard interface for linking music synthesizers and instruments together. Computers, fitted (оснащенный) with MIDI interface boards can be connected to MIDI instruments to allow the music to be stored on computer and to be played.

Earlier there was a giant problem with the photos: as time goes by old pictures became yellow, and their quality worsened (ухудшаться). Now this is not a problem anymore: digital photos don’t lose their quality.

JPEG (Joint Photographic Experts Group) is an image format, developed specially for storing photos and other pictures which has a lot of colors. Each pixel in this format takes 24 bits, so it can represent over 16 millions of colors. Storing BMP files with color depth 24 bits per pixel occupies a lot of disk space, however JPEG files requires much less storage. It is achieved by complicated compression algorithm which is used by JPEG format. It greatly reduces file size, however it has one disadvantage - this algorithm is lossy (с потерями). It means that when you save to JPEG some artifacts are appeared in the image. It is often imperceptible (незаметный) to the human eye, however if you set high compression ratio (or low quality) or recompress JPEG image for many times, it may become noticeable.

JPEG is a format which works well for natural scenes, such as scanned photographs. It provides good Quality/Disk space ratio.

In conclusion, I want to say that the most common formats are MPEG, JPEG and MP3. Nowadays the majority of all films are compressed, using the MPEG4 format. In every music shop you could find the whole MP3 collection of albums of your favorite artist on only one CD. The majority of all music that can be downloaded from the Internet is compressed using the MP3 technology. And if you check the format of your digital photos, made by digital camera you will notice, that they are compressed into the JPEG format.

That’s all.

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