MMC MPEG4

MPEG - 4

Aim of this assignment is to introduce to the possibilities that MPEG-4

offers for the creation of interactive scenes. To reach this aim the MPEGfamily

will be introduced, followed by a more detailed description of the

possibilities of MPEG-4 and an example scenario that could be build

using MPEG-4.

The MPEG formats define standards for digital video and audio services.

Since the available bandwidth for transferring the contents is the limiting factor nowadays, the aim of the MPEG is to define a standard that allows to reduce the necessary bandwidth, without loosing the main benefit of digital transmission which is transmission without losses in quality. To achieve this the MPEG has defined methods for compression of audio and video signals. To enhance the standard more functionality has been added. So today the MPEG standard covers not only a stream of video and audio data, but also the definition of multimedia objects that can be placed - even interactively - in a scene.

The MPEG is a group of experts that develops standards for digital video and audio. It’s members are working for many companies and therefor the standards proposed by this group are widely accepted.3.1 MPEG-13.2 MPEG-23.3 MPEG-43.4 MPEG-7 and MPEG-21

3.1 MPEG-1 :During development of MPEG-1 the aim was to allow the storage of video and audio with a bandwidth of up to 1.5 Mbits per second. This would allow to store approximately a movie on a CD. The standard was approved in 1992 and has been a great success. A very well known part of this standard is MP3. This allows to compress music to 10 percent of it’s size using physical properties (or imperfections) of the human ear. The reduced size allows fast distribution over the Internet which is a problem for the right holders. MPEG-4 tries to cope with this problem by introducing possibilities for DRM.

3.2 MPEG-2: Two years later in 1996 MPEG-2 was approved.

MPEG-2 is today’s standard for a broad number of applications of which the main are digital television and the DVD. The MPEG-2 standard is not only implemented in software, but also in hardware. This allows the exchange between a range of systems. For example video can be directly coded to MPEG-2 and then be viewed with a computer or a digital video recorder. Today a hole industry is based on MPEG-2. A huge amount of money is turned over in connection with MPEG-2.

3.3 MPEG-4:MPEG-3 does not exist since during the development it was recognized that MPEG-2 was already fulfilling the needs of HDTV5. So MPEG-2 was extended and MPEG-3 was skipped. This fact is the origin of the curios numbering of the following MPEG standards. The development of MPEG-4 was started in 1993 and is still ongoing. The first two versions have be produced. The versions 3, 4 and 5 are subject of current development. According to [1] MPEG-4 builds on theproven success of three fields:

1. Digital television;2. Interactive graphics applications (synthetic content);3. Interactive multimedia (World Wide Web, distribution of

and access to content)MPEG-4 provides the standardized technological elements enabling the integration of the production, distribution and content access paradigms of the three fields.

3.4 MPEG-7 and MPEG-21:MPEG-7 is a standard for describing multimedia content data. It is not aimed at any one application in particular; rather, the elements that MPEG-7 standardizes support as broad a range of applications as possible. The vision for MPEG-21 is to define a multimedia framework to enable transparent and augmented use of multimedia resources across a wide range of networks and devices used by different communities.

This following subsections will cover the main points of MPEG-46. Based on those the following section will show an example how the possibilities of MPEG-4 can be used.

4.1 Audio:MPEG 4 supports natural and synthesized sounds. Both can be parted in general audio signals and speech only signals. All those signals can have variable bit rates to be adjustable to the the available transmission channel..The quality reaches from intelligible speech up to high quality multichannel radio. The most interesting feature is the support for TTS. This allows to only transmit the text itself that is much smaller that a recorded version. This text can be somewhere in a range from pure text to text with additional information about the gender, age, dialect and pronunciation. An important feature is the possibility to synchronize the sound with the actual picture that is presented to the user. The second important feature is the scalability of audio signals. This can be done by parsing the source before transferring to save bandwidth or at the decoders site to adjust the sound to the sound system of the user.

4.2 Visual:The visual content of MPEG-4 can be parted in different objects. Apart from the classical moving pictures possible objects are still 2D images that may be a background or 3D objects that can be placed in the foreground. Those objects can be composed to larger groups. Another possible object is an animated face. In combination with TTS for example complete synthesized news can be realized. Like the TTS encoder the face animator can be customized. It is possible to use a completely synthesized face or a face that consists of a texture map where the textures may come from a real person.

4.3 Combining audio and visual objects:Unlike it’s predecessors MPEG-4 is not only a linear stream of data that is displayed to the end user. The stream consists of multi media objects that are placed in a three dimensional space. Objects in this space may be grouped together to a complete scene. An example of this van be seen in section 5. So the end users application has to calculate a resulting image and sound that is presented to the user. Having all the objects separated from each other interactivity can be added.

4.4 Interactivity:The user may change his view and listening point. The video and sound is then recalculated with the user’s new coordinates. It is possible for example to revolve a scene to see more details. Other interactions may be like in adventure games to activate objects by clicking on them. This feature can be very useful in educational programs to allow the users explore a topic on their own.

4.5 Profiles:Profiles are used to adjust the implementation to the needs of an application. The profiles are subsets of a complete implementation of all defined standards in MPEG-4. According to the user’s needs only a limited part of the MPEG-4 standard has to be implemented. If the implementation is within a specific profile it’s conform to MPEG-4 even if it may implement not all methods for visual objects. A PDA or mobile phone is an example for such a restricted device since the computational power of such devices are quiet restricted. So the focus will be on the quality of the sound.

4.6 Intellectual property management :Since it is important to have possibilities to identify and protect intellectual property MPEG-4 works on the definition of syntax and tools to support this[3]. In MPEG-4 there exist possibilities to store unique identifiers of media objects. These identifiers can either be key-value pairs that contain for example >>composer<</>>John Smith<< or numbers that are issued by ISAN9, ISRC10 or others. By assigning each object it’s own identifier, it is possible to protect only parts of the content and leave other parts for free use. Additionally MPEG-4 offers a standardized interface to use systems that control access to intellectual property. This doesn’t mean that MPEG-4 protects the intellectual property itself, but it provides the possibility to insert information about intellectual property during authoring and to retrieve this information at the end user’s application.

This section will show how MPEG-4 may be used. For this a scenario of a possible application will be created and the methods and possibilities of MPEG-4 will be shown.

5.1 The scenario:The scenario is a news broadcast on digital television. The scene is illustrated in the below diagram. The news reader is filmed in front of a ’blue screen’. Then he’s projected in front of a still image. On the left side different contributions are inserted. Possible contributions can be a small film or another still image. Another possibility would be to animate a face of a reporter could be animated using textures from pictures of him. This could be useful if only a telephone line is available to transmit the news from regions with weak infrastructure. It would even be possible to let the end user’s system create the speech with a TTS decoder.

A possible scenario

3D video Augmented reality Telepresence Scientific visualization Virtual reality …

The room is generated in computer

What has not been covered in this assignment is the problematic use fee. Another point that was not covered is the delivery of streaming data and it’s according layers. MPEG-4 offers great possibilities for the future. The idea of interactive scenes is very attractive. But the standard will be useless until it’s in products that can be sold on the mass market. What will help to introduce MPEG-4 faster is the possibility to manage the rights of the authors. This is a major requirement nowadays since the music and movie industry has neglected this topic a long time and had concentrated on complaining about the users using the possibility to copy the contents without loss.

Thank You