MPEG-4 Video Standard Rate Control
1.
Introduction
2.
Functionality of MPEG-4 Video
3.
Rate control method
4.
Simulation result
5.
Conclusion
6.
Future work
7.
VQ 投影片
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1. Introduction
1.1 MPEG-4 AV Object
Multimedia Scene composed of “objects”
- Natural & SNHC A/V
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2-D & 3-D Graphics
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- Animated face, text
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Arbitrary shapes or rectangular
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Encoding the object independently
Coding scheme can differ for individual objects
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From low bit-rates to (virtually) lossless quality
1.2 Feature of MPEG-4
Error Resilience
- Access on mobile networks (efficient coding and low bit
rates still important)
Scalable Coding
- Scalability based on (audio/visual) objects
- Different quality,priority,error protection for different
objects possible
Intellectual Property Rights (IPR)
- Identification (V.1) and protection (V.2)
1.3 MPEG-4 vs other video standard
Existing Standards
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H.261：frame-based,low bit rates
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H.263：frame-based,very low bit rates
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MPEG2： frame-based, high bit rates
MPEG-4
- Object-based
- From very low bit rates to very high bit rates
- Both natural and synthetic
- Interactive at object level
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1.4 Data Structure in Visual Part of MPEG-4
1.5 MPEG-4 Video Decoding
1.6 MPEG-4 Video Tools
2. Functionality of MPEG-4 Video
Content-Based Interactive
Coding Efficiency Parameter
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5 kbits/s - 5 Mb/s
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Resolution：
small ~ DTV
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Progressive/Interlace
Error Resilience/Robustness
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Mobile Environments
Scalability
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Spatial and Temporal
2.1 Scalability
Object scalability
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Achieved by the data structure used and the shape coding
Temporal scalability
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Achieved by generalized scalability mechanism
Spatial scalability
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Achieved by generalized scalable mechanism
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2.2 Scalable Coding General Scheme
2.3
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Temporal scalability
The temporal scalability is achievable for both rectangular frames
and arbitrarily shaped VOPs
The base layer is encoded conventional MPEG-4 video
The enhancement layer is encoded using one of the following two
mechanisms：
- type 1
- type2
2.3.1 Temporal Enhancement Type
2.3.2
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Temporal scalability
Type 1
Only a portion of the VOP in the base layer is enhanced
2.3.3
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Temporal scalability
Type 2
The entire VOP in the base layer is enhanced
2.4
Spatial scalability
The base layer is coded as conventional MPEG-4 video
The enhancement layer is encoded using prediction
mechanisms from the base layer
3. Rate control method
Coding Scalability
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Object Scalability
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Spatial / Temporal Scalability
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SNR Scalability
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SNR Scalability
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Set target bit rates → decide quantization level
3.1 Quantization
Method 1: Similar to that of H.263
Method 2: Similar to that of MPEG-2
Optimized non-linear quantization of DC coefficients
Quantization matrices and loading mechanism
3.2 Configuration parameter for rate control
General parameter
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Type of control (fixed QP,VM4,VM5+,….)
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Control algorithm (global or individual,different algorithm
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Statistical models for rates and distortion
in each case)
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Parameter for global control
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Global bit rates
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Buffer size
Parameter for individual control
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Bit-rate per VO
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Buffer size for each VO
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3.3 Selection of type
Fixed QP
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For each type of VOP (I,P,B)：no rate control
VM4
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Primitive version of RC,work independently for
every VOP
VM5+
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All other algorithm (for either global or independent control)
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TM5
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MPEG2 algorithm
4. Simulation result
4.1 Simulation Environments
Program:
Momusys Version 2.0
Akiyo_qcif.yuv
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150 Frames
4.2 Simulation Result
Global
target bit rate =
2
buffer size
5. Conclusion
MPEG-4 more smart and flexible
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content-based interactive
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bit-stream editing
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scene authoring
More Functionality
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For error-prone environments
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For rate control
6. Future work
Keep studying MPEG4 and its program
Understanding all the parameter in the .ctl .cfg file
Encode multiple objects into a visual scene
Familiar with scalable technology and rate control method
D
iscuss deliver MPEG4 bit-streams over internet issues
