MPEG4

1
MPEG-4

• Making Video Smaller

2
What is MPEG

• Moving Pictures Experts Group
• Established 1988
• In charge of the developing standards of coded
  representations of digital audio and video.
• http//www.chiariglione.org/mpeg/index.htm
• Standards
• Earliest MPEG-1
• In Development MPEG-21

3
Goals of MPEG

• Primary Goal
• Compression of multimedia to low bitrates with
  minimal distortion
• Predicted Applications
• Interactive CDs
• Digital Audio Broadcast
• Actual Applications
• Audio and Video compression
• MP3, AAC, MPEG
• Digital Television

4
Eight Final Functionalities

• Content-Based Multimedia Access Tool
• Provides access and organization tools for
  audiovisual data
• Content-Based Manipulation and Bitstream Editing
• Enable users to edit files without full
  decompression
• Hybrid Natural and Synthetic Data Coding
• Compress both filmed and artificially produce
  images, at the same time if necessary

5
Eight Final Functionalities(part 2)

• Improved Temporal Random Access
• Allows for access to any point in the file
• Improved Coding Efficiency
• Creates a smaller file
• Better suited for low bandwidth transmission
• Coding of Multiple Concurrent Data Streams
• Allow viewers to not only view but interact with
  file
• Allows for multiple points of view and audio
  tracks

6
Eight Final Functionalities(part 3)

• Robustness in Error-Prone Environments
• Must include error correcting codes
• Content-Based Scalability
• Decoder should be able to scale back quality,
  resolution, and bitrate depending on situation

7
An Introduction to MPEG

• Types of Pictures
• I Independent
• A frame coded independently. Also known as an
  intra frame.
• P Predictive
• A frame coded based upon its predecessor. Also
  known as an inter frame.
• B Bidirectional
• A frame coded based upon both the preceding and
  following frames

8
Application of Picture Types

• Only I frames must be explicitly coded
• P and B frames are much smaller but are more
  error prone
• These frames may contain as little as motion
  displacement variable or differencing information
  for a small portion
• Any error in transmission/decoding continues to
  propagate until the next I frame

9
The 3 Layers

• System Data Layer
• Reads data and sends it to the appropriate one of
  the other layers
• Video and Audio Layers
• Consist of decoders to properly interpret data
  sent by the system.

10
MPEG Structure

• Video Sequence
• An entire video file
• Consists of one or more groups of pictures (GOP)
• Which are further divided into individual
  pictures
• Which are subdivided into slices
• Which are again subdivided into macroblocks

11
Macroblocks

• Macro blocks are made up of three blocks
• One is a 16 x 16 block of luminance
• This is the grayscale version of the image
• Changes in this block are most apparent to the
  viewer
• Subdivided into four 8 x 8 blocks
• Two are 8 x 8 blocks of matching chrominance
  samples
• These blocks are then compressed using a discrete
  cosine transformation (DCT)

12
History Lesson

• MPEG-1
• First adopted as an international standard in
  1993
• Most well known today for MPEG layer 3 (MP3)
• MPEG-2
• First adopted as an international standard in
  1996
• MPEG-4
• First adopted as an international standard in 1999

13
Looking Ahead

• MPEG-7
• Designed specifically to transport multimedia
  files over the web
• MPEG-21
• The Multimedia Framework
• Focused on
• Distribution Standard
• User Interaction

14
Current Applications - AAC

• Audio only compression using MPEG-4 layer 3
• In essence, the new version of MP3
• Clearing up a confusion
• AAC does not imply iTunes was the origin
• AAC has no default DRM

15
Current Applications Video

• MPEG-4 can compress
• as low as 5 kbits/s
• Appropriate for short, quick transmissions at low
  quality
• Well suited for file transfer over the web
• As high as 1 Gbit/s
• High quality
• Used in HDTV

16
Bibliography

• Salomon, David.  Data Compression The Complete
  Reference, 3rd Edition.       New York
  Springer-Verlag New York, Inc., 2004MPEG Home
  Page       http//www.chiariglione.org/mpeg/index
  .htmOverview of the MPEG-4 Standard.     
   Edited by Rob Koenen, March 2002     
   http//www.chiariglione.org/mpeg/standards/mpeg-4
  /mpeg-4.htmKoenen, Rob.  From MPEG-1 to
  MPEG-21 Creating an InteroperableMultimedia
  Infrastructure.       December 2001.     
   http//www.chiariglione.org/mpeg/from_mpeg-1_to_m
  peg-21.htm

17
Bibliography

• MPEG Industry Forum       http//www.m4if.org/
  Frerichs, David.  New MPEG-4 High-efficiency AAC
  Audio Enabling newapplications.       April
  2003.       www.telos-systems.com/techtalk/
  hosted/m4-in-3010020(M4IF_HE_AAC_paper).pdfThe
  Streaming Media Technology Resource     
   http//www.mpeg4.net/Tudor, P.N.  MPEG-2 Video
  Compression.       Electronics Communication
  Engineering Journal, December 1995     
   http//www.bbc.co.uk/rd/pubs/papers/paper_14/pape
  r_14.htmlVideo Compression Resources     
   http//datacompression.info/Video.shtml