MPEG Digital VideoCoding Standards

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MPEG Digital Video-Coding Standards
by Alberto Rodriguez
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Outline

• Motivation and history for MPEG
• Basic review of concepts and techniques (MPEG)
• MPEG Video Compression
• Basic Elements of MPEG-2,4

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Development of MPEG Standards

• MPEG - Moving Picture Experts Group

• Motivation
• VLSI technology advances.

• History
• 1980s - CCITT, CCIR, ISO/IEC (Standardization
  activities)
• 1988 - MPEG
• Coded Representation of Moving
  Pictures, Audio.
• Targeted Bit Rate of 1.5Mbits/s
• 1992 - MPEG-1 was finally released.
• 1994 - MPEG-2 Video Quality.
• Quality between NTSC/PAL and CCIR 601.
• Targeted Bit Rate 2-10Mbits/s
• 1998 - MPEG-4

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Development of MPEG Standards

• Success
• Generic Structure and flexibility
• Flexible Picture Size and Frame Rate
• Standard
• Decoder
• Bit Stream formats
• MPEG-4
• Low Rates - 5-64 Kbits/s (Mobile/ PSTN)
• High Rates target 4Mbits/s (TV)
• Universal Accessibility and Robustness
• High Interactive Functionality
• Coding of Natural and synthetic data
• High Compression Efficiency

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Fundamentals of MPEG

• Redundancy
• Statistical
• Subjective
• Vision
• VLSI technology foreseen for the lifecycle of
  the standard
• Lossless vs. Lossy
• Lossless - Maintain a video quality.
• Lossy - Meet a target bit rate subject to and
  optimization criterion.

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The MPEG Video-Coder Source Model

• Nature
• Statistical
• Redundancies in Space and Time
• Correlation between pixels in time and/or space
• DCT (8x8) blocks to explore correlation
• Intraframe Correlation
• DPCM (Differential Pulse Code Modulation)
• Hybrid Combination (DPCM/DCT)

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Subsampling and Interpolation

• Temporal Subsampling

time

• Spacial Subsampling

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Motion Compensated Prediction

• Temporal Redundancies (MPEG-1 and MPEG-2)
• Prediction Error and Motion Vector
• Motion Estimation (Not pel by pel but in blocks).
• High Spatial Correlation between pels.
• Better than intraframe reductions.

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Transform Domain Coding

• Compression Method.
• De-correlate the intra- and inter- frame.
• Encode transformed coefficients
• c AbAt (Unitary Linear Transformation)
• Why DCT
• High decorrelation and fast DCT algorithms
  available
• Objectives of TDC
• Make coefficients ( c ) as small as possible.
• Reduce dependencies between coefficients
• MPEG DPCM/DCT Hybrid

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The MPEG-1 Standard

• CD/ROM interactive systems.
  Video over telecomm. Networks
• Flexibility
• Free selection of picture size, frame rate and
  others.
• Constraints
• Decoder
• Support Video Source Parameter up to TV size.
• Minimum 720 pels/line.
• Minimum 576 lines.
• Frame Rate of 30 frames/s.
• Minimum Bit rate of 1.86 Mbits/s.
• Non Interlaced Video Format
• JPEG, H.261
• Commonality with CCITT H.261
• Additional Capabilities
• Frame based Random Access.
• FF/FR Searcher , Reverse Playback
• Editability of compressed bit rates

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MPEG-1 Coding Scheme

• Hybrid DPCM/DCT
• Intraframe and Interframe coding techniques.
• Compression
• Macroblock Structures (MB)
• Motion Compensation
• Conditional Replenishment
• Possibility to update macroblock information
  (decoder)
• only if needed.
• Skipped MB
• Inter MB
• Intra MB
• Rate Control
• Quantization Step Size is variable.
• Rate control algorithm is not part of the
  standard.

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Specific Storage Media Functionalities

• Random Access
• FF/FR (Frame Forward and Frame Reverse)
• Concept of B Pictures
• I - Random Access, FF, FR. Trade off - Low
  compression
• P- Generated form other frame ( I or P)
• B- Interpolation
• Optional transmission
• I I I I I I I I
• I P P P . P I P P P P
• I B B P B B PB B P I

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MPEG-2 Standard

• Added functionality and quality to support
  prediction of
• of interlaced coding.
• Scalable Video.
• Profiles and Levels
• Good for equipments that cannot support the full
  implementation
• Profiles
• Define a new set of algorithms
• Levels
• Range of parameters

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MPEG-2 Non/Scalable Modes

• NON-Scalable
• MAIN - Obvious extension of MPEG-1.
• Field/ Frame Prediction
• Better Chrominance Representation
• MPEG-1 411 MPEG-2 422
• Scalable
• Interoperability - Flexibility of supporting
  receivers with
• different display capabilities.
• Ex. HDTV/ SDTV
• Scalable Profiles
• SNR
• Allows two layers of scalability / DCT.
• Spatial
• Allows two layers. (Pyramidal Approach for
  Progressive Video)

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MPEG-4

• Universal accessibility and robustness in error
  prone environments.
• High interactive functionalities.
• Coding of natural and synthetic data.
• Compression Efficiency.
• Content Based Interactivity
• Some MPEG-4 Standards
• Low bit transmission ( 5-64 Kbits/s)
• ( 64 Kbits/s - 4 Mbits/s)
• Video Object Planes
• Introduces a very high degree of flexibility.
• Sprite Coding Technology
• Efficient transmission of background scenes
  where the changes with in
• the background is created by camera movements.