Mpeg4 is an ISO/IEC which was developed by MPEG (Moving Pictures Experts Group).This version was finalized in the October 1998 and it became an international standard in the begning of the year 1999. Mpeg4 is a set of compression and decompression standards. It is also a streaming technique that delivers rich media over narrow and broadband networks.
Features of MPEG4
1. Interoperability: – This standard is not specific to one platform but it is designed for all platforms.
2. Scalibility: – Mpeg4 allows for flexibility in the way bit streams are coded. Decoding a particular bit stream and the resolution of the content can be optimized to the networking enviourment and display device.
3. Profiles: – Mpeg4 offers different technology profiles for different applications. In this way service providers need not use the entire set of technologies, but only the subset that suits their applications.
Principle of MPEG4
It aims to achieve its objectives by applying certain rinciples to the way the data is represented. MPEG4 relates to the components that comprise a multimedia scene as ndividual media objects. For example a sound track, imation, video or images are all individual media objects. These media objects can be grouped together to form ompounded objects. These are the building blocks of multimedia scenes. But these media objects are one part of the MPEG4 stream. Apart from this, there is additional information also that governs how the objects are to be rendered on the screen and how they are to be transmitted on the different networks. For this purpose MPEG4 includes stream description information and also coding information. The stream description information describes the relation between the media objects like sound track, animation, video or images and their representation on the screen. The coding information indicates how the media objects are linked to resources that are transmitting the media objects.
MPEG4 standard comprises of several core parts:
1. MPEG4 systems: – This part of the standard describes the scene description, multiplexing, synchronization and protection of multimedia information. It specifies the way in which mpeg video and mpeg audio are integrated. It also introduces the concept of BIFS (Binary Format for Scene).BIFS is a binary format for 2d or 3d audio visual content. It is based on ‘VRML'(Virtual Reality Modeling Reality), which is a file format for representing 3d vector graphics designed particularly for WWW (World Wide Web).
2. Delivery of multimedia:-This part of the standard specifies the quality of media streaming
3. MPEG4 visual: This part of the standard specifies the representation of visual objects.
4. MPEG4 video: This part of the standard specifies the representation of video objects.
All the information related to media objects, scene description or control information is contained in elementary streams. These elementary streams are information carriers. Elementary streams contain tags or pointers called object descriptors which determine how an mpeg4 stream is decoded at the receiving station. Descriptors enable receiving stations to recognize the type of media that is being streamed.
Another important term in mpeg4 is:-
DMIF (Delivery Multimedia Integration Framework): MPEG-4 has been designed for a wide range of applications and bit rates. This standard deals with delivery and compression in two separate architectures. The architecture that governs delivery is called DMIF (Delivery Multimedia Integration Framework).DMIF specifies how the MPEG-4 stream interfaces with different networking technologies and protocols.DMIF provides the overall delivery structure of MPEG-4 streams. DMIF covers areas such as Quality of Service (QOS), broadcast requirements. The bridge between DMIF and MPEG-4 Systems is called DAI (DMIF Application Interface).
MPEG-4 has several characteristics that make it the ideal standard for streaming rich media over the Internet.
1. For the narrowband Internet, content can be compressed at rates as low as 24 Kbit/s.
2. MPEG-4 allows for scalability, which means the same content can be streamed to heterogeneous networks.
In addition to MPEG-4, other digital video and audio formats are currently used in streaming rich media. Some of the other streaming formats are:-
Real Video and RealAudio from Real Networks
Real Video and RealAudio are video and audio compression technologies developed by Real Networks for media streaming over low bandwidths, mainly the Internet.
Microsoft Netshow/ Windows Media Technologies (WMT)
WMT is a video and audio compression technology developed by Microsoft for streaming media over the Internet.
QuickTime
QuickTime is a file format and streaming architecture that stores, streams and plays media files.Stored and streamed media is compressed with compression schemes.