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ABSTRACT
As more and more audiovisual information becomes available from many sources around the world, many people would like to use this information for various purposes. This challenging situation led to the need for a solution that quickly and efficiently searches for and/or filters various types of multimedia material that’s interesting to the user.
For example, finding information by rich-spoken queries, hand-drawn images, and humming improves the user-friendliness of computer systems and finally addresses what most people have been expecting from computers. For professionals, a new generation of applications will enable high-quality information search and retrieval. For example, TV program producers can search with “laser-like precision” for occurrences of famous events or references to certain people, stored in thousands of hours of audiovisual records, in order to collect material for a program. This will reduce program production time and increase the quality of its content.
MPEG-7 is a multimedia content description standard, (to be defined by September 2001), that addresses how humans expect to interact with computer systems, since it develops rich descriptions that reflect those expectations.
INTRODUCTION
The Moving Pictures Experts Group abbreviated MPEG is part of the International Standards Organization (ISO), and defines standards for digital video and digital audio. The primal task of this group was to develop a format to play back video and audio in real time from a CD. Meanwhile the demands have raised and beside the CD the DVD needs to be supported as well as transmission equipment like satellites and networks. All this operational uses are covered by a broad selection of standards. Well known are the standards MPEG-1, MPEG-2, MPEG-4 and MPEG-7. Each standard provides levels and profiles to support special applications in an optimized way.
It's clearly much more fun to develop multimedia content than to index it. The amount of multimedia content available -- in digital archives, on the World Wide Web, in broadcast data streams and in personal and professional databases -- is growing out of control. But this enthusiasm has led to increasing difficulties in accessing, identifying and managing such resources due to their volume and complexity and a lack of adequate indexing standards. The large number of recently funded DLI-2 projects related to the resource discovery of different media types, including music, speech, video and images, indicates an acknowledgement of this problem and the importance of this field of research for digital libraries.
MPEG-7 is being developed by the Moving Pictures Expert Group (MPEG) a working group of ISO/IEC. Unlike the preceding MPEG standards (MPEG-1, MPEG-2, MPEG-4) which have mainly addressed coded representation of audio-visual content, MPEG-7 focuses on representing information about the content, not the content itself.
The goal of the MPEG-7 standard, formally called the "Multimedia Content Description Interface", is to provide a rich set of standardized tools to describe multimedia content.
A single standard which can provide a simple, flexible, interoperable solution to the problems of indexing, searching and retrieving multimedia resources will be extremely valuable and widely deployed. Resources described using such a standard will acquire enhanced value. Compliant hardware and software tools capable of efficiently generating and interpreting such standardized descriptions will be in great demand.
DIFFERENT VIDEO FORMATS
Avid PC users will almost certainly remember the first time they were able to view a video clip on their computer. The clips were about the size of a postage stamp and were generously referred to as "multimedia". Later, the first acceptable video clips were used in the opening scenes of computer games. In some cases, there were even digital 3D animations that couldn't be created in real-time with the hardware and software that was available in those days. As the video clips demanded extensive storage space (despite their short length), they were only available on CD-ROM drives that had recently become popular. Because of this, many PC's became multimedia-compatible, in a restricted sense, by the integration of a CD-ROM drive and a soundcard. However, their limitations soon became apparent: it wasn't possible to run the video clip smoothly in fullscreen mode even with the most powerful hardware available. With the development of high performance graphic chips, faster processors and corresponding software interfaces, today's users are now able to run video clips in all the usual formats (including fullscreen mode) without problems. We'll continue with a look at the most video formats and we'll then provide an overview of their specific applications.
The AVI Format
One of the oldest formats in the x86 computer world is AVI. The abbreviation 'AVI' stands for 'Audio Video Interlaced'. This video format was created by Microsoft, which was introduced along with Windows 3.1. AVI, the proprietary format of Microsoft's "Video for Windows" application, merely provides a framework for various compression algorithms such as Cinepak, Intel Indeo, Microsoft Video 1, Clear Video or IVI. In its first version, AVI supported a maximum resolution of 160 x 120 pixels with a refresh rate of 15 frames per second. The format attained widespread popularity, as the first video editing systems and software appeared that used AVI by default. Examples of such editing boards included Fast's AV Master and Miro/Pinnacle's DC10 to DC50. However, there were a number of restrictions: for example, an AVI video that had been processed using an AV Master could not be directly processed using an interface board from Miro/Pinnacle. The manufacturers adapted the open AVI format according to their own requirements. AVI is subject to additional restrictions under Windows 98, which make professional work at higher resolutions more difficult. For example, the maximum file size under the FAT16 file system is 2 GB. The FAT32 file system (came with OSR2 and Windows 98) brought an improvement: in connection with the latest DirectX6 module 'DirectShow', files with a size of 8 GB can (at least in theory) be created. In practice however, many interface cards lack the corresponding driver support so that Windows NT 4.0 and NTFS are strongly recommended. Despite its age and numerous problems, the AVI format is still used in semi-professional video editing cards. Many TV cards and graphic boards with a video input also use the AVI format. These are able to grab video clips at low resolutions (mostly 320 x 240 pixels).
Apple's Format
The MOV format which originated in the Macintosh world, was also ported to x86 based PC's. It is the proprietary standard of Apple's Quicktime application that simultaneously stores audio and video data. Between 1993 and 1995, Quicktime was superior to Microsoft's AVI format in both functionality and quality. The functionality of the latest generation (Quicktime 4.0) also includes the streaming of Internet videos (the realtime transmission of videos without the need to first download the entire file to the computer). Despite this, Apple's proprietary format is continually losing popularity with the increasing use of MPEG. Video clips coded with Apple's format are still found on some CD's because of Quicktime's ability to run on both Macintosh and x86 computers.
MPEG Formats
The MPEG formats are by far the most popular standard. MPEG stands for "Motion Picture Experts Group" - an international organization that develops standards for the encoding of moving images. In order to attain widespread use, the MPEG standard only specifies a data model for the compression of moving pictures and for audio signals. In this way, MPEG remains platform independent. One can currently differentiate between four standards: MPEG-1, MPEG-2, MPEG-4 und MPEG-7. Let's take a brief look at each format separately.
MPEG-1 was released in 1993 with the objective of achieving acceptable frame rates and the best possible image quality for moving images and their sound signals for media with a low bandwidth (1 MBit/s up to 1,5 MBit/s). The design goal of MPEG-1 is the ability to randomly access a sequence within half a second, without a noticeable loss in quality. For most home user applications (digitizing of vacation videos) and business applications (image videos, documentation), the quality offered by MPEG-1 is adequate.
MPEG-2 has been in existence since 1995 and its basic structure is the same as that of MPEG-1, however it allows data rates up to 100 MBit/s and is used for digital TV, video films on DVD-ROM and professional video studios. MPEG-2 allows the scaling of resolution and the data rate over a wide range. Due to its high data rate compared with MPEG-1 and the increased requirement for memory space, MPEG-2 is currently only suitable for playback in the home user field. The attainable video quality is noticeably better than with MPEG-1 for data rates of approximately 4 MBit/s.
MPEG-4 is one of the latest video formats and its objective is to get the highest video quality possible for extremely low data rates in the range between 10 KBit/s and 1 MBit/s. Furthermore, the need for data integrity and loss-free data transmission is paramount as these play an important role in mobile communications. Something completely new in MPEG-4 is the organization of the image contents into independent objects in order to be able to address or process them individually. MPEG-4 is used for video transmission over the Internet for example. Some manufacturers plan to transmit moving images to mobile phones in the future. MPEG-4 is intended to form a platform for this type of data transfer.
MPEG-7 is the latest MPEG family project. It is a standard to describe multimedia data and can be used independently of other MPEG standards. MPEG-7 will probably reach the status of an international standard by the year 2001.
The MJPEG Format
The abbreviation MJPEG stands for "Motion JPEG". This format is practically an intermediate step between a still image and video format, as an MJPEG clip is a sequence of JPEG images. This is one reason why the format is often implemented by video editing cards and systems. MJPEG is a compression method that is applied to every image. Video editing cards such as Fast's AV Master or Miro's DC50 or the much more inexpensive Matrox Marvel product series reduce the resulting data stream of a standard television signal from approximately 30 MB/s (!) to 6 MB/s (MJPEG file). This corresponds to a compression ratio of 5:1. However, a standard for the synchronization of audio and video data during recording has not been implemented in the MJPEG format so that the manufacturers of video editing cards have had to create their own implementations.
WHAT ARE THE MPEG STANDARDS?
The Moving Picture Coding Experts Group (MPEG) is a working group of the Geneva-based ISO/IEC standards organization, (International Standards Organization/International Electro-technical Committee) in charge of the development of international standards for compression, decompression, processing, and coded representation of moving pictures, audio, and a combination of the two. MPEG-7 then is an ISO/IEC standard being developed by MPEG, the committee that also developed the Emmy Award-winning standards known as MPEG-1 and MPEG-2, and the 1999 MPEG-4 standard.
• MPEG-1: For the storage and retrieval of moving pictures and audio on storage media.
• MPEG-2: For digital television, it’s the timely response for the satellite broadcasting and cable television industries in their transition from analog to digital formats.
• MPEG-4: Codes content as objects and enables those objects to be manipulated individually or collectively on an audiovisual scene.
MPEG-1, -2, and -4 make content available. MPEG-7 lets you to find the content you need.
Besides these standards, MPEG is currently also working in MPEG-21 a Technical Report about Multimedia Framework.