Transport Of Mpeg-4 - MULTIMEDIA

The design of MPEG - 4 was motivated by multimedia applications on the WWW. In particular, multimedia (text, graphics, audio, video, etc.) objects and scene descriptions (temporal and spatial relationships of the video objects) can be transmitted by the server and interpreted and reassembled at the client side, to drastically reduce multimedia data transmitted onto the WWW. This section briefly describes the Delivery Multimedia Integration Framework (DMIF) and the issue of MPEG - 4 over IP.

DMIF in MPEG - 4

DMIF is an interface between multimedia applications and their transport. It supports remote interactive network access (IP, ATM, PSTN, ISDN, or mobile), broadcast media (cable or satellite), and local media on disks.

The interface is transparent to the application, so a single application can run on different transport layers, as long as the right DMIF is instantiated.

The following figure shows the integration of delivery through three types of communication mediums.As shown, the local application interacts with a uniform DMIF Application Interface (DAI), which translates the application's requests into specific protocol messages, to be transported through one of the three types of mediums.

When the delivery is through a network, the DMIF is unaware of the application. In fact, an additional DMIF Network Interface (DNI) is needed, to take care of their signaling messages for specific networks.

When delivering multimedia data, DMIF is similar to FTP. First, a SETUP session is established with the remote network site. Second, streams are selected and a STREAM request is sent to the DMIF peer, which returns a pointer to a separate connection where the streaming will take place. Third, the new connection is established, and data is streamed.

In the scenarios of Broadcast and Local storage, the application will know how the data is stored and delivered. Hence, this becomes part of the DMIF implementation.

DMIF has built - in QoS monitoring capability. It supports (a) continuous monitoring, (b) specific QoS queries, and (c) QoS violation notification.

DMIF - the multimedia content delivery integration framework

DMIF - the multimedia content delivery integration framework

MPEG - 4 over IP

The specifications on MPEG - 4 over IP networks are jointly developed by the MPEG and IETF as a framework in Part 8 of MPEG - 4 (ISO / IEC 14496 - 8) and an Informative RFC in IETF.

MPEG - 4 sessions can be carried over IP - based protocols such as RTP, RTSP, and HTTP. Details regarding RTP payload format are specified by IETF RFC 3016. In short, generic RTP payload format defines a mapping between logical MPEG - 4 SL packets and RTP packets, and FlexMuxpayload format maps FlexMux packetized streams to RTP packets.


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