MPEG-2 Standard (1994) (ISO/IEC 13818). ○ Extension for interlace, optimized
for TV resolution. (NTSC: 704 x 480 Pixel). ○ Image quality similar to NTSC, ...
Overview: Video Coding Standards
Video coding standards: applications and common structure Relevant standards organizations ITU-T Rec. H.261 ITU-T Rec. H.263 ISO/IEC MPEG-1 ISO/IEC MPEG-2 ISO/IEC MPEG-4 Recent progress: H.264/AVC
Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 1
ISO/IEC MPEG
MPEG-1 Standard (1991) (ISO/IEC 11172) z z z z
MPEG-2 Standard (1994) (ISO/IEC 13818) z z z
Target bit-rate about 1.5 Mbps Typical image format CIF, no interlace Frame rate 24 ... 30 fps Main application: video storage for multimedia (e.g., on CD-ROM) Extension for interlace, optimized for TV resolution (NTSC: 704 x 480 Pixel) Image quality similar to NTSC, PAL, SECAM at 4 - 8 Mbps HDTV at 20 Mbps
MPEG-4 Standard (1999) (ISO/IEC 14496) z z
Object based coding Wide-range of applications, with choices of interactivity, scalability, error resilience, etc.
Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 2
MPEG-1/2: GOP Structure
"Group of Pictures" = “GOP“, GOP structure is very flexible
I-Picture
P-Picture
P-Picture
B-Pictures time
1
3
4
2
6
Bernd Girod: EE398B Image Communication II
7
8
5
Video Coding Standards: MPEG-1,2,4 no. 3
MPEG-1 Encoder
Preprocessing
Picture reordering
-
DCT
Weighting
Quantization
VLC
Inverse quantization Inverse weighting
Video in
Inverse DCT
Video multiplex
Buffer
Motion vectors, macroblock info, start codes Bitstream
+
zero Picture store 1
1/2
+
Motion compensation Picture store 2
Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 4
MPEG-1: coding of I-pictures
I-pictures: intraframe coded 8x8 DCT Arbitrary weighting matrix for coefficients Differential coding of DC-coefficients Uniform quantization Zig-zag-scan, run-level-coding Entropy coding Unfortunately, not quite JPEG
Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 5
MPEG-1: coding of P-pictures
Motion-compensated prediction from an encoded I-picture or P-picture (DPCM) Half-pel accuracy of motion compensation, bilinear interpolation One displacement vector per macroblock Differential coding of displacement vectors Coding of prediction error with 8x8-DCT, uniform threshold quantization, zig-zag-scan as in I-pictures
Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 6
MPEG-1: coding of B-pictures
Motion-compensated prediction from two consecutive P- or I-pictures z
either • only forward prediction (1 vector/macroblock)
z
or • only backward prediction (1 vector/macroblock)
z
or • Average of forward and backward prediction = interpolation (2 vectors/macroblock)
Half-pel accuracy of motion compensation, bilinear interpolation Coding of prediction error with 8x8-DCT, uniform quantization, zig-zag-scan as in I-pictures Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 7
MPEG-2 vs. MPEG-1
Efficiently compress interlaced digital video at broadcast quality z z z z z z
Field/frame pictures Chroma sampling New prediction modes Field/frame DCT Additional scan patterns for DCT coefficients Motion compensation with blocks of size 16x8 pels
Improved coding efficiency by different quantization, VLC tables Various scalability modes
Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 8
Coding of Interlaced Video (1)
Frame and field picture structures
Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 9
Coding of Interlaced Video (2)
Field prediction for field pictures
Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 10
Coding of Interlaced Video (3)
Field prediction for frame pictures 16
16 8
16
8
Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 11
Coding of Interlaced Video (4)
Dual prime for P pictures
Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 12
Coding of Interlaced Video (5)
Field/frame DCT Alternate Scan
Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 13
MPEG-4
Support highly interactive multimedia applications as well as traditional applications Advanced functionalities: interactivity, scalability, error resilience… Coding of natural and synthetic audio and video, as well as graphics Enable the multiplexing of audiovisual objects and composition in a scene ¾
‘TV/film’ AV-data
¾ ¾ ¾
‘Computer’ Interactivity
‘Telecom’ Wireless
¾ ¾
Bernd Girod: EE398B Image Communication II
Video on LANs, Internet video Wireless video Video database Interactive home shopping Video e-mail, home movies Virtual reality games, flight simulation, multi-viewpoint training Video Coding Standards: MPEG-1,2,4 no. 14
MPEG-4: Scene with audiovisual objects
Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 15
MPEG-4: Video coding
Basic video coding z
z
Definition of Video Object (VO), Video Object Layer (VOL), Video Object Plane (VOP) Improved coding efficiency vs. MPEG-1/2 • Based on H.263 baseline • Global motion compensation • Sprites • Quarter pixel motion compensation
Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 16
MPEG-4: Video coding
Object-based video coding z
Binary shape coding
z
α-map shape coding
z z
Padding for block-based DCT of texture Shape-adaptive DCT
DWT for still texture coding Mesh animation, face and body animation
Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 17
Shape Adaptive DCT
Bernd Girod: EE398B Image Communication II
Video Coding Standards: MPEG-1,2,4 no. 18
