In computer science, we understand the user interface as the interactive input and output of a computer as it’s is perceived and operated on by users. Multimedia user interfaces are used for making the multimedia content active. Without user interface the multimedia content is considered to be linear or passive.
Multimedia user interfaces are computer interfaces that communicate with users using multiple media modes such as written text together with spoken language.
Multimedia would be without much value without user interfaces. The input media determines not only how human computer interaction occurs but also how well. Graphical user interfaces – using the mouse as the main input device – have greatly simplified human-machine interaction.
General Design Issues
The main emphasis in the design of multimedia user interface is multimedia presentation. There are several issues which must be considered.
1. To determine the appropriate information content to be communicated.
2. To represent the essential characteristics of the information.
3. To represent the communicative intent.
4. To chose the proper media for information presentation.
5. To coordinate different media and assembling techniques within a presentation.
6. To provide interactive exploration of the information presented.
Video at the User Interface
A continuous sequence of, at least, 15 individual image per second gives a rough perception of a continuous motion picture. At the use interface, video is implemented through a continuous sequence of individual images. Hence, video can be manipulated at this interface similar to manipulation of individual still images.
When an individual image consisting of pixels (no graphics, consisting of defined objects) can be presented and modified, this should also be possible for video (e.g., to create special effects in a movie). However, the functionalities for video are not as simple to deliver because the high data transfer rate necessary is not guaranteed by most of the hardware in current graphics systems.
Audio at the User Interface
Audio can be implemented at the user interface for application control. Thus, speech analysis is necessary.
Speech analysis is either speaker-dependent or speaker-independent. Speaker dependent solutions allow the input of approximately 25,000 different words with a relatively low error rate. Here, an intensive learning phase to train the speech analysis system for speaker-specific characteristics is necessary prior to the speech analysis phase.
A speaker-independent system can recognize only a limited set of words and no training phase is needed.
During audio output, the additional presentation dimension of space can be introduced using two or more separate channels to give a more natural distribution of sound. The best-known example of this technique is stereo.
In the case of monophony, all audio sources have the same spatial location. A listener can only properly understand the loudest audio signal. The same effect can be simulated by closing one ear. Stereophony allows listeners with bilateral hearing capabilities to hear lower intensity sounds. It is important to mention that the main advantage of bilateral hearing is not the spatial localization of audio sources, but the extraction of less intensive signals in a loud environment.
