Multi Media Services
A multimedia service must allow the user to play multimedia data from voice or video acquisition crossing a chain of ICT systems. Two methods are used, the full reference and the no reference.
The full reference (FR) method consists in comparing the quality of reference signal from the source (perfect signal) with the received signal (degraded signal). FR measures deliver the highest accuracy and repeatability. However, FR measures can be applied to dedicated tests only in live networks.
The no reference (NR) method uses a degraded signal without information about the reference signal. From the NR method, some characteristics of a conversation, such as voice, gender, background noise, and so on, can be identified.
A multimedia service is a combination of two or more media components such as voice, data, video, and still image, in a single session delivered between two or more parties. Multimedia services can be classified as interactive or distribution services. User interaction defines the behavior of interactive services. Distribution services, on the other hand, are broadcast-based. There are three categories of interactive services: conversational, messaging, and retrieval.
Conversational services are based on user-to-user interaction. To maintain parity with human perception, these services are usually bi-directional with low end-to-end delays. Media synchronization is required to avoid low delay variation such that there are no perceived gaps or jitter. Real-time responses are required and there is no need for any store and forward of data.
Messaging services also provide user-to-user communication. However, it requires a store and forward mechanism, such as a mailbox or a mail server. Multimedia messaging services can support video, audio, text, and still images, individually or in combination.
Multimedia Distribution services are based on broadcast services. These can be delivered with or without user presentation control. Distribution services without user control are simple broadcast services such as audio or video. The multimedia information is transmitted from a central point. The user has no ability to control the timing or delivery of the content. To support user control, the distribution services broadcast content by using sequence numbering and repetitive transmission. This allows the user to control the presentation of content in terms of sequence and delivery of the content.