M P E G

A Presentation by Sebastian Graf and Thomas Winterscheid

Topics • What is MPEG?

• Different MPEG Standards • What is a movie?

• The MPEG video compression • Conclusion

What is MPEG?

What is MPEG exactly?

• „Moving Picture Experts Group“ • Established in 1988 • The convener of the MPEG group is Dr. Leonardo Chiariglione • Vice president of Multimedia Telecom Italia Lab http://leonardo.telecomitalialab.com/

What is MPEG exactly?

• Comission directed by ISO an IEC • Develops standards for video and audio coding • Nickname given to a family of international standards

Approved MPEG Standards • MPEG-1 Nov. `92 • MPEG-2 Nov. `94 • MPEG-4 • Version 1 Oct. `98 • Version 2 Dec `99

Planned for the future...

• MPEG-4 • Version 3,4 and 5 • MPEG-7 • MPEG-21

MPEG-1 • Quality ~ VHS – video • Originally for 1x CD-ROM drives (1,4 MBit/s) • Constant datarate • Standard for Video CDs

MPEG-2 • HDTV (High Definition TeleVision) • Premiere World (lower rates for more chan.) • Still important for new digital TV norms • DVD • Variable datarates

MPEG-3 ?

• MPEG-3 standard was under construction, but never finished • Was planned for newer HDTV • Parts of technology and techniques are implemented in MPEG-2

Datarate/ Resolution Overview Advantages Disadvantages Scope MPEG-1

1,4 Mbit/325x288 High Compression Audiocodec Assymetric compression Only in SIF Format Codec for Multimedia files on your PC

MPEG-2

4 Mbit/325x288 15 Mbit/720x576 60 Mbit/1440x1152 80 Mbit/1920x1152 Different Formats Supports Dolby Surround Much more complicated as MPEG-1 Multimedia PC Digital TV Satellite TV

The Future: MPEG-7 • Planned to be released in fall 2001 • Is formally called „Multimedia Content Description Interface“ • Includes a new standard of handling DDL • More easier to implement into multimedia • Intends to be an allrounder for all multimedia formats

The Future: MPEG-7 • MPEG 1-2-4 won`t be replaced by MPEG-7 • Works indepentend of it`s predecessors • Because of file description data query in special multimedia databank is possible • Several search options will be included • But this isn`t enough................

More Future: MPEG-21 • Development is running, planned to be finished in 2003 • Includes a new description language (DIDL) • Universal player for all standards • Multimedia files are more communicative • And also there is to say...............

More Future: MPEG-21 The general goal of MPEG-21 activities is to describe an open framework which allows the integration of all components of a delivery chain necessary to generate, use, manipulate, manage, and deliver multimedia content across a wide range of networks and devices.

http://ipsi.fhg.de/delite/Projects/MPEG7/Mpeg21.html

Topics • What is MPEG?

• Different MPEG Standards • What is a movie?

• The MPEG video compression • Conclusion

What is a movie?

video track

timecode

audio track

What is a movie?

timecode

• encoder encode or decode?

• decoder 100111010011 100111010011

MPEG video compression movie picture 1 movie picture 2

MPEG video compression • High similarity of 2 successive pictures • =>

correlation

• Same pixel´s movement in Camera turns • =>

motion compensation

• DCT & quantization

MPEG video compression

The block layer • Picture is divided in 8x8 blocks (JPEG) • The blocks are processed independent from each other • DCT • Quantization

DCT & Quantization • Very similar to the fourier transformation • Information are transformed to a frequenz exhibition (nearly no data loss) • Matrix of DCT-coefficients • Coefficients are divided by quantization values (given by the JPEG group) and then rounded to the next integer value

Discrete Cosinus Transformation 200 150 100 50 0 0 50 100 150 200 250 65 -125 -314 -503 0 50 100 150 200 250

The macro layer • I – Frame, P – Frame or B – Frame?

The macro layer • I – Frames: • „intra coded image“ • highest amount of data • coding is very similar to a JPEG picture • can be processed independent from other frames • have a specified distance to the next I-Frame

The macro layer • B – Frames: • „bi-directionally interpolated image“ • lowest amount of data • most frequent type of frame • depending on the previous or following P / I-Frame • can also depend on the previous and following frame

The macro layer • P – Frames: • „predicted image“ • medium amount of data • difference to the previous I – Frame is stored • have motion compensation ability

The macro layer • Motion Compensation in P – Frames : I - Frame P - Frame

The slice layer • Slices are a group of succesive macro blocks • There is no dependence of slices on each other

The picture layer Display I B B P B B P I P Datastream B B P B B

The „group of picture“ layer • Unrestricted number of pictures in their natural sequence • At least one I-Frame per GOP • Quantization values can be different for each GOP

The sequence layer • Union of GOPs • Movie width • Movie height • Movie format (e.g. 4:3 / 16:9) • Framerate (fps) • Bit-rate

Conclusion • MPEG is a very common standard • Look forward to the new codec technologies • Contains numerous new features • New standards will be much more user friendly • Many options to adjust the compression • Even better techniques for even better quality

Any questions?

[email protected]

Thanks for your attention...