▁from ▁interpol ated ▁pixels ▁by ▁an ▁interpol ator ▁filter ▁to ▁horizontal ▁and ▁vertical ▁directions . ▁ ▁Multiple ▁references ▁ ▁Multiple ▁references ▁to ▁motion ▁estimation ▁allows ▁finding ▁the ▁best ▁reference ▁in ▁ 2 ▁possible ▁buff ers ▁( List ▁ 0 ▁to ▁past ▁pictures , ▁List ▁ 1 ▁to ▁future ▁pictures ) ▁which ▁contain ▁up ▁to ▁ 1 6 ▁frames ▁in ▁total . ▁Block ▁prediction ▁is ▁done ▁by ▁a ▁weight ed ▁sum ▁of ▁blocks ▁from ▁the ▁reference ▁picture . ▁It ▁allows ▁en hanced ▁picture ▁quality ▁in ▁scenes ▁where ▁there ▁are ▁changes ▁of ▁plane , ▁zoom , ▁or ▁when ▁new ▁objects ▁are ▁revealed . ▁ ▁En hanced ▁Direct / Sk ip ▁Mac ro block ▁ ▁Sk ip ▁and ▁Direct ▁Mode ▁are ▁very ▁frequently ▁used , ▁especially ▁with ▁B - frames . ▁They ▁significantly ▁reduce ▁the ▁number ▁of ▁bits ▁to ▁be ▁c oded . ▁These ▁modes ▁are ▁referred ▁to ▁when ▁a ▁block ▁is ▁c oded ▁without ▁sending ▁resid ual ▁error ▁or ▁motion ▁vectors . ▁The ▁enc oder ▁will ▁only ▁record ▁that ▁it ▁is ▁a ▁Sk ip ▁Mac ro block . ▁The ▁dec oder ▁will ▁dedu ce ▁the ▁motion ▁vector ▁of ▁Direct / Sk ip ▁Mode ▁c oded ▁block ▁from ▁other ▁blocks ▁already ▁dec oded . ▁ ▁There ▁are ▁two ▁ways ▁to ▁dedu ce ▁the ▁motion : ▁▁ ▁Tem por al ▁It ▁uses ▁the ▁block ▁motion ▁vector ▁from ▁List ▁ 1 ▁frame , ▁located ▁at ▁the ▁same ▁position ▁to ▁dedu ce ▁the ▁motion ▁vector . ▁List ▁ 1 ▁block ▁uses ▁a ▁List ▁ 0 ▁block ▁as ▁reference .