▁whole ▁process ▁graph ically : ▁ ▁This ▁kind ▁of ▁prediction ▁has ▁some ▁pros ▁and ▁cons : ▁ ▁If ▁everything ▁goes ▁fine , ▁the ▁algorithm ▁will ▁be ▁able ▁to ▁find ▁a ▁matching ▁block ▁with ▁little ▁prediction ▁error ▁so ▁that , ▁once ▁transformed , ▁the ▁overall ▁size ▁of ▁motion ▁vector ▁plus ▁prediction ▁error ▁is ▁lower ▁than ▁the ▁size ▁of ▁a ▁raw ▁encoding . ▁ ▁If ▁the ▁block ▁matching ▁algorithm ▁fails ▁to ▁find ▁a ▁suitable ▁match ▁the ▁prediction ▁error ▁will ▁be ▁considerable . ▁Thus ▁the ▁overall ▁size ▁of ▁motion ▁vector ▁plus ▁prediction ▁error ▁will ▁be ▁greater ▁than ▁the ▁raw ▁encoding . ▁In ▁this ▁case ▁the ▁enc oder ▁would ▁make ▁an ▁exception ▁and ▁send ▁a ▁raw ▁encoding ▁for ▁that ▁specific ▁block . ▁ ▁If ▁the ▁matched ▁block ▁at ▁the ▁reference ▁frame ▁has ▁also ▁been ▁encoded ▁using ▁Inter ▁frame ▁prediction , ▁the ▁errors ▁made ▁for ▁its ▁encoding ▁will ▁be ▁propag ated ▁to ▁the ▁next ▁block . ▁If ▁every ▁frame ▁was ▁encoded ▁using ▁this ▁technique , ▁there ▁would ▁be ▁no ▁way ▁for ▁a ▁dec oder ▁to ▁synchron ize ▁to ▁a ▁video ▁stream ▁because ▁it ▁would ▁be ▁impossible ▁to ▁obtain ▁the ▁reference ▁images . ▁ ▁Because ▁of ▁these ▁draw back s , ▁a ▁reliable ▁and ▁time ▁periodic ▁reference ▁frame ▁must ▁be ▁used ▁for ▁this ▁technique ▁to ▁be ▁efficient ▁and ▁useful . ▁That ▁reference ▁frame ▁is ▁known ▁as ▁In tra - frame , ▁which ▁is ▁strictly ▁int ra ▁c oded , ▁so ▁it ▁can ▁always ▁be ▁dec oded ▁without ▁additional ▁information . ▁ ▁In ▁most ▁designs , ▁there ▁are ▁two ▁types