在AV1中，帧间预测的插值滤波一共定义了以下五种类型

interpolation filter	名称
0	EIGHTTAP_REGULAR
1	EIGHTTAP_SMOOTH
2	MULTITAP_SHARP
3	BILINEAR
4	switchabe

typedef enum ATTRIBUTE_PACKED {EIGHTTAP_REGULAR,EIGHTTAP_SMOOTH,MULTITAP_SHARP,BILINEAR,// Encoder side only filtersMULTITAP_SHARP2,INTERP_FILTERS_ALL,SWITCHABLE_FILTERS = BILINEAR,SWITCHABLE = SWITCHABLE_FILTERS + 1, /* the last switchable one */EXTRA_FILTERS = INTERP_FILTERS_ALL - SWITCHABLE_FILTERS,INTERP_INVALID = 0xff,
} InterpFilter;