SuJin Lee

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ITU-T H.26X Standardsfrom K.R. Rao,
Multimedia Communication Systems, Prentice Hall
PTR, USA, 2002

• Su-Jin Lee
• 2004-10-30
• Super Computing Lab.

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Contents ?

• Introduction
• Video Coding Standards
• H.26X Standards
• H.261
• H.263
• H.263
• H.26L
• Conclusion

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Introduction (1) ?

• H.26X Standards
• Defined by ITU-T (International Telecommunication
  Union- Telecommunication Standardization Sector)
• Video-coding standards
• For video communications via videophone
• In terms of coding algorithms, all video-coding
  standards follow a similar framework.

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Introduction (2) ?

• H.26X Standards (Cont.)

Call Control
Video Coding
System Control
Audio Coding
Data
Multimedia Multiplex and Synchronization
Network Adaptation
Network Interface
? General protocol stack of H-series audiovisual
communication terminal
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Video-coding Standards (1) ?
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Video-coding Standards (2) ?
near-term goal
H.263
H.263
H.263
H.261
H.26L
H.264
long-term goal

• Near-term Goal
• To enhance H.261 using the same general framework
• Long-term Goal
• To design a video-coding standard that may be
  fundamentally different from H.261
• To achieve further improvement in coding
  efficiency

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H.261 (1) ?

• Features
• For video telephony and video conferencing
  applications
• Since 1984 bit rates px384Kb/s (p1..5)
• ? 1988 bit rates px64Kb/s (p1..30)
• Framework
• Motion compensation to remove temporal redundancy
  
• Transform coding to reduce spatial redundancy

• H.261 has very significant influence on many
  other existing and evolving video-encoding
  standards.

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H.261 (2) ?

• Specification
• The frame rate 29.97 frames/sec
• Picture formats CIF and QCIF
• YCbCr mode (420)
• One macroblock (MB) total six 8x8 blocks
• Four 8x8 blocks of Y pels(pixels)
• One 8x8 block of Cb pels and one 8x8 block of Cr
  pels

1
2
5
6
3
4
Y
Cb
Cr
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H.261 (3) ?

• Specification (Cont.)
• 1 GOB(Group of Blocks) 33 MBs
• 1 picture 12 or 3 GOBs

QCIF
CIF
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H.261 (4) ?

• Compression of video data
• For spatial redundancy DCT
• For temporal redundancy Motion Compensation

DCT
Q
Video IN
Video OUT
spatial
IDCT
Motion Compensation
Loop filter
temporal
H.261 Encoder
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H.263 (1) ?

• Features
• Since 1993, adopted in 1996
• For applications with bit rates lower than 64Kb/s
• Ex) PSTN, the mobile network (from 10 to 24 Kb/s)
• Performance
• Can provide a 3 to 4 dB gain over H.261 at bit
  rates below 64Kb/s
• Can give a 30 bit-rate saving compared with
  MPEG-1
• The first international standard for video
  compression that would permit video
  communications at such a low rate.

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H.263 (2) ?

• Compared with H.261, H.263
• supports more picture formats
• sub-QCIF, QCIF, CIF, 4CIF, and 16 CIF
• uses different GOB structures
• A GOB always contains at least one full row of
  MBs.
• uses half-pel motion compensation, not using loop
  filtering
• Interpolation
• performs motion vector(MV) prediction
• The median of the 3 neighboring predictors
• Specifies four options
• Unrestricted MV mode, arithmetic-coding mode,
  advanced prediction mode, and PB-frame mode

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H.263 (3) ?
MV2
MV3
? GOB structures
MV1
MV
? MV prediction
sub-QCIF
CIF
QCIF
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H.263 ?

• Features
• A revision of the original 1999 version of the
  H.263
• Modification
• Quantization mode
• Motion vector range depending on the frame size
• The addition of rounding term to the equation for
  half-pel interpolation
• A wider variety of input video formats
• Adding arbitrary frame sizes, in multiples of
  four from 32x32 to 2,048x1,152
• and so on

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H.263 ?

• Features
• A revision of the original 1999 version of the
  H.263
• Modification
• Quantization mode
• Motion vector range depending on the frame size
• The addition of rounding term to the equation for
  half-pel interpolation
• A wider variety of input video formats
• Adding arbitrary frame sizes, in multiples of
  four from 32x32 to 2,048x1,152
• And so on

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H.26L (1) ?

• Features
• From 1998 to 2002
• To seek efficient video-coding algorithms that
  can be fundamentally different from the MC-DCT
  framework
• Developed to H.264(AVC) in 2003
• SK Telecom, LG Electronics and other venture
  companies have taken part in standardization
  since 2001.

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H.26L (2) ?

• Aims
• At very low bit-rate
• Real-time
• Low end-to-end delay coding for a variety of
  source materials
• Low complexity permitting software implementation
• Enhanced error robustness

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H.26L (3) ?

• Proposals
• Modified prediction/tranform-based method
• Loop-filtering method
• Adaptive scalar quantizer scheme using
  nonzero-level codebooks
• Data partitioning using data-reordering algorithm
• Video coding using long-term memory for multiple
  reference frames and affine motion-compensated
  prediction
• and so on

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H.26L (4) ?

• Example
• Multihypothesis (MH) picture type
• Each block of it can be compensated by a linear
  combination of two motion-compensated blocks.
• In contrast to B-picture, this use temporally
  previous pictures and cause no extra coding
  delay.

I
MH2
MH3
MH4
B
P
I
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H.26L (5) ?

• Example (Cont.)
• MH Block Pattern one or two hypotheses
• Seven MH MB types are added to the standardized
  MB types for intercoding

mode1
mode2
mode3
mode4
mode5
mode6
mode7
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Conclusion ?

• H.26X Standards
• started from video-telephony and conferencing
• Especially contributes the compression of
  rectangle video frames
• H.261/H.263 vs H.264
• All video coding standards specify
• only the bit-stream syntax
• how a decoder should interpret the bit-stream to
  decode the image
• not how the encoding should be done
• ? Do anything for more effective encoding systems!

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Thank you for your listening!