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motion-compensated prediction. Inter-layer motion, residual or intra prediction
mechanisms can be used to improve the coding efficiency of the enhancementlayers.In
inter-layermotionprediction,forexample,theup-scaledbaselayermotiondata isemployed
forthespatialenhancementlayercoding.
Quality scalability can be considered as a subset of spatial scalability where two or more
layersarehavingsimilarspatialresolutionsbutdifferentqualitylevels.Thescalableexten-
sion of H.264/AVC also supports quality scalability using coarse-grain scalability (CGS)
and medium-grain scalability (MGS). CGS is achieved using spatial scalability concepts
with the exclusion of the corresponding up-sampling operations in the inter-layer predic-
tion mechanisms. MGS is introduced to improve the flexibility of bit-stream adaptation
and error robustness.
