12.3.3Third part of CE9 "Temporal motion vector memory compression"
There was one primary contribution on this subject, which was JCTVC-D072 (with a cross-check in JCTVC-D232). MVs have been stored on a basis as small as a 4x4 basis (up to 2 MVs per block). This proposal reportedly reduces the necessary storage by a factor of 16 by storing them on a 16x16 basis instead. A coding efficiency impact averaging approximately 0.5% was reported.
Decision: This simplification was adopted (as the memory savings is very substantial).