MPEG-2. Scalability Support. Nimrod Peleg Update: Dec.2000. MPEG-2 Target. “...Generic coding method of moving pictures and associated sound for ...digital storage, TV broadcasting and communication...” Dedicated for high quality services e.g. HDTV, Networked data services etc.
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MPEG-2 Scalability Support Nimrod Peleg Update: Dec.2000
MPEG-2 Target • “...Generic coding method of moving pictures and associated sound for ...digital storage, TV broadcasting and communication...” • Dedicated for high quality services e.g. HDTV, Networked data services etc. • Eveloped from CCIR-601, CCIR-648, JPEG, H.261 and MPEG-1 former standards
MPEG-2 Btstream structure Sequence Sequence Sequence Seq. Hdr. Seq. Ext. Ext.&User GOP GOP GOP Header Ext.&User Picture Data Picture Data Pic. Hdr. Pic. Coding Ext. Ext.&User Slice Slice Slice Header Macroblock Macroblock Macroblock Hdr. Block Block Block
Scalability Modes • SPATIAL SCALABILITY • TEMPORAL SCALABILITY • SNR SCALABILITY • DATA PARTITIONING
SNR Scalability • Refinement of the DCT coeffs. encoded in base layer by the enhancement layer coeffs. • Base layer containes coarser quantization then enhancement layer • Only non intra quant. matrices are used in the enhancement layer • Enhancement layer contains coded refinement DCT coeffs. and a small overhead
SNR Scalability (Cont’d) • DCT coeffs. in base layer are added to DCT coeffs. in enhancement layer • The combined layer decoding process is identical to decoding of a non-scalable bitstream • Different rate control for the 2 layers
SNR Scalability Scheme Lower Layer Code VLC Inverse Scan Inverse Quant + Enahncement Layer Code VLC Inverse Scan Inverse Quant Decoded Samples Inverse DCT Motion Compensation Frame Storage Memory
Data Partitioning • The bitsteam is split into 2 layers: partition0, partition1 • The Priority Breakpoint (in sequence header) indicates which syntax elements are placed in partition0 which is the base or high priority partition
Data Partitioning (Cont’d) • The remainder of the bitstream is placed in partition1 which is the low priority partition • Seq.,GOP,picture and slice headers are duplicated from partition0 to partition1 • VBV refers to the sum of the 2 partitions • Partition0 contains sequence scalable extension
Quant Scale DCT coeff2 DC coeff DCT coeff1 DCT coeff3 EOB DC coeff DCT coeff1 EOB Quant Scale DC coeff DCT coeff1 DC coeff DCT coeff1 Partition0 DCT coeff2 DCT coeff3 EOB EOB Partition1 Data Partitioning (Cont’d) • No Data Partitioning • Partitions for Priority Break Point 64:
Data Partitioning (Cont’d) Possible Breakpoints: • After slice header • After macroblock address increment (macroblock header) • Before coded block pattern (after Motion Vector) • After any number of DCT coefficients (excluding one)