Multimedia - Basic Concept

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Multimedia is a term that is made up of two words: multi = many; media = transfer system and present the message. Thus, the presentation of content that users can simultaneously perceive using your senses and options available (vision, hearing, smell, touch, taste, movement, action). It can be argued that the beginnings of this perception of content dating back to the home of silent film, in which a soundtrack using an ordinary piano, for the purpose of creating an interesting, attractive and realistic image messages to be transferred. Since this is the atmosphere during the comprehension of such content, it is clear that the purpose of media content to engage as many human senses, mostly about fun, although it can be used in scientific, artistic, educational, promotional or other purposes. Concert of a 'band', with lots of colorful lights and intertwined and 'merry' laser beam, is also a multimedia experience. And even protest meeting with various banners, using a megaphone, is a kind of multimedia event.

According to the above, the basic elements of multimedia content are:

• Text - A set of colorful letters deliberately used to send of some message, but it is static and linear (linear), and must be read :-). But modern computer technology, as they use the web, using hypertext, the text can be activated (e.g. mouse click) to perform an action.
• Sound - One of the basic elements of multimedia, whether it's vocal or instrumental track. Dynamic content, like music, can be very impressive.
• Picture - As a drawing or photograph, has a significant role in multimedia. It belongs to the static content, but a good drawing or photograph can present the message more effectively than hundreds of words.
• Video - A series of pictures made and presented by special devices, with the addition of audio content, as well as movie, the most interesting is a dynamic multimedia content. A sense of reality of the content is very great. Of course, the most effective with regard to convey messages to the user as dynamic content. With stereoscopic video, which requires two channels to transmit content, or two overlapping layers of video, with special glasses can be obtained and displayed a sense of spaciousness.
• Animation - A series of drawings (10-25 frames per second) that quickly turns, and if the alternate fast enough (over 50 frames per second with repeated single), some good optical illusion of motion due to inertia of our eye. What can not be shown in movie or practically feasible in life, in the animation is possible. That's why kids love this dynamic eyesight of presenting the message, because it's practically a fantasy world.
• Interactivity - If a new message is associated only with a previous message, it is a reaction. But if there are more messages, and among them there is a mutual connection and allows the user to control the way that are displayed it is a matter of the interaction. The user can control the arrival and departure of the necessary messages; dynamic atmosphere.

In today's world full of multimedia computing technologies are presented in very different ways. Different from the original text and image content that are sequentially alternated as 'Power Point' presentation slides change according to the slide projector, a modern multimedia includes a combination of text, speech, music, images, animations, video, and user interactivity. These facilities can, for example, the computer contained a set of separate files that can be considered as a dedicated program designed to support, which is presented to the user via:

• Specialized of software on the computer.
• Devices that are able to transmit, process and display multimedia content.

Files on a computer can be, for example video content that is considered a dedicated support program, which know how to use hardware accelerated graphics card and monitor display subtitles i.e. subtitles, as the 'WinDVD' (Figure 1.1a). They can only be music content will be read as a program support 'Winamp' (Figure 1.1b). There is also a series of groups of software that allows you to view and create multimedia content, as well as their record on the media, as 'Roxio Creator' (Figure 1.1c). All of the above, and so belongs to the first group.

Figure** 1.1 Software products WinDVD / WinAMP / Roxio Creator. ( + / - )

The peculiarity of the above is developed that requires user interactivity via either a keyboard or a joystick, GAMES, a kind of product that they need remarkable skills in respect of its making, and its use. In the modern world of the Internet, enables 'group play' means of dedicated servers for the specific game. In the Internet world it is possible to use other multimedia content, and the most interesting devices to the user an easy and enable. Games are a very effective way of amusement. Suitable for children can effect a didactically well-designed games that teach and do not promote violence. Gaming devices have long been known and shown in Figure 1.2 is one of the most popular gaming devices, the forerunner of today's computer games - pinball.

	Figure 1.2 Pinball.

Chasing metal balls, either with a new device or through computer simulations, it is very suitable for undemanding pastime. Las Vegas is known in the United States is a place where plenty of play room with presented device. For home use has long used video game consoles, which are connected to a TV set may provide an effective interactive gaming, or just watching movies. In Figure 1.3 shows a few.

Figure 1.3 Video game consoles Xbox, PlayStation and Wii.

Row, from left to right are shown in game consoles Microsoft Xbox, Sony PlayStation and Nintendo Wii. If we add 'steering wheels with pedals' and similar gaming atmosphere can be very realistic. And the mobile device can be used for gaming. With the application of wireless technology used by SOHO - Wi‑Fi environment (for example, the image 4.4.100b), it's even simpler. What is the required throughput capacity of the communication channel to display content such as HDTV?

If you see an HDTV content on a TV set appropriate resolution of 1920 x 1080, this means that the screen has 2'073'600 an RGB triodes, respectively 2'073'600•3 = 6'220'800 display elements that need to be monitored. If the video display contains 50 frames per second, and 25 in a way that each image appears 2 times in a row, it means that we should define 311'040'000 records and unit time. Let each element defines a triode with color depth of 8 bits (BR usual notation) then must be transferred from the source to the destination 2'488'320'000 bits. Of course, that amount of data can be efficiently transmitted in its original form, it is necessary to compressing data before sending the reverse process of reception. That's what worried CODEC (short for COder-DECoder) - a device or program support, which converts analog voice or video signal into a digital sequence (stream) of bits and vice versa using one of the methods of compression. To transfer audio and video codec developed a multitude that have different characteristics, particularly with regard to data compression.

Today's standard 'MPEG-4 AVC' (H.264) and 'MPEG-4 AAC' encode-decode HDTV video and audio content. For videos used sampling of 8-14 bits, and requires the bandwidth with compression up to 10 Mbps, or up to 20 Mbps for 3D content, audio content and for the necessary bandwidth of 320 kbps for 5.1 audio the system. This is not a rule but an average, for a very rich dynamic content will be almost twice the bandwidth, which means that the potential 'bottlenecks' when viewing multimedia content via wireless networks. There is no video transmission that requires a little more closely bandwidth SOHO devices from 100 Mbps (100BASE-T) per port. Most ISP's connection to the SOHO device to 9 Mbps, which is enough to use or viewing of simpler or less demanding multimedia content from the Internet (Skype, Netflix, YouTube, etc.), with a possible 'twitching' images when viewing content in HD quality.

Even though, in practice, has shown that playing video content much more stable when used internal network served by SOHO device 1000BaseT Ethernet port's and which has implemented the supervision and control of the distribution of multimedia content via UPnP (Universal Plug and Play) protocol, which used by almost all the current multimedia devices, enabling functional service regarding the distribution of multimedia content through the internal network. The foundation for UPnP networking is IP addressing. From SOHO device that allows DHCP service multimedia device using UPnP takes the free IP address of its identification in the network, and then search the related devices via SSDP (Simple Service Discovery Protocol) protocol that allows devices advertise their services. Defined through 'control points' in the network, in this case SOHO device with adequate program support, retrieved and distributed desired services and facilities that multimedia devices on the network offered by appropriate action (a set of commands and parameters) delivered to devices. So in some way it is a more efficient upgrade based on the TCP / IP protocol regarding connecting multimedia devices and manage their content. In a similar manner using the DNS service for offline content.

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