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Slide 1
Briefly introduction to image/ video coding standard and FGS
for MPEG-4
Slide 2
Video Compression Standards ITU-T International
Telecommunication Union Telecommunication Standardization (ITU-T)
MPEG Moving Picture Experts Group
Slide 3
International Telecommunication Union Telecommunication
Standardization (ITU-T) CCITT H.261 ITU-T Study Group 15 Videophone
and video conferencing 1988-1990: p x 64 kbps (p = 1 30) ITU-T
H.263 PSTN and mobil network: 10 to 24 kbps 1994: H.263, H.263+
ITU-T H.26l Merging to JVT in MPEG-4 Part 10
Slide 4
MPEG: Moving Picture Experts Group Coding of Moving Video and
Audio MPEG-1: CD-I, for Digital Storage, -1992 MPEG-2: + TV, HDTV,
for Broadcast 1994 MPEG-3: HDTV -> merged into MPEG-2 MPEG-4:
Coding of Audiovisual Objects-V.1:1998; V.2:1999 Extensions ongoing
MPEG-7: MM Description Interface Fall 2001 Describing audiovisual
material MPEG-21: Digital Multimedia Framewrok 1 st parts early
2002 The Big Picture and The Glue
Slide 5
Block-Based Coding Why divide to blocks? Image->Blocks
Slide 6
H.261 Video Formats Video Forma t Luminance (Y)Chrominance(Cb,
Cr) pixels/lin e lines/fram e pixels/linelines/fram e
CIF352288176144 QCIF1761448872 Y pixel Cb, Cr pixel Block
boundary
Basis of Transform Basis vectors{v 1,v 2, ,v n } Orthogonal :
(v i ) (v j ) = 0 if i!=j Normalized : (v i ) (v i ) = 1
Orthonormal : orthogonal and normalized eg. orthonormal :
{(0,1),(1,0)} Orthogonal : {(1,1),(-1,1)}
Slide 12
Why DCT is used for image compressing KLT(Karhunen-Loeve
transform): Statistically optimal transform: minimal MSE for any
specific bandwidth reduction KLT depends on the type of signal
statistics No fast algorithm DCT approaches KLT for highly
correlated signals: sample values typically vary slowly from point
to point across an image =>Highly correlated signals Fast
algorithm(but not optimal)
Video Compression Encoder For Still Image TQ Entropy coding
Image block Transform Coefficients Zigzag Scan (2D->1D)
Bitstream Encoder For Video Sequence Q -1 T -1 Reconstructed
Transform Coefficients Reconstructed Image block MC -
Slide 26
H.261 Intra frame frame information Inter frame reference frame
motion vector
Slide 27
H.261 Coder DCTQ Inverse DCT Motion Compensation Loop Filter
Video in Inverse Q
FGS USING BIT-PLANE CODING OF DCT COEFFICIENTS Overall Coding
Structure of FGS Some Details of FGS Coding Profile Definitions in
the Amendment of MPEG-4
Slide 44
Overall Coding Structure of FGS FGS encoder structure
Slide 45
Overall Coding Structure of FGS FGS decoder structure
Slide 46
Some Details of FGS Coding 1)Different Numbers of Bit-Planes
for Individual Color Components 2)Variable-Length Codes 3)Decoding
Truncated Bitstreams
Slide 47
Different Numbers of Bit- Planes for Individual Color
Components
Slide 48
Variable-Length Codes Statistics of the (RUN, EOP) symbols in
the four VLC tables
Slide 49
Coding patterns for syntax element fgs_cbp
Slide 50
Slide 51
Decoding Truncated Bitstreams Decoding of the truncated
bitstream is not standardized in MPEG-4. One possible method To
look ahead 32 bits at every byte-aligned position in the bitstream.
If the 32 bits are not fgs vop start code, the first 8 bits of the
32 bits are information bits of the FGS frame to be decoded. The
decoder slides the bitstream pointer by one byte and looks ahead
another 32 bits to check for fgs vop start code.