Video Guide Part 3: Video Formats and Compression Methods

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.