commit b8a6fd6be732f483e3ade2154b491e44ae48fbc7
author hui su <huisu@google.com> Wed May 10 10:57:57 2017 -0700
committer hui su <huisu@google.com> Sat May 20 15:29:38 2017 -0700
tree 68c4fef62e269ad2f5568443f54b4bf0810ddc44
parent 90ed98f98ac46339ec34c0e6f5db2a4ee97482e4

DPCM intra coding experiment

Encode a block line by line, horizontally or vertically. In the vertical
mode, each row is predicted by the reconsturcted row above;
in the horizontal mode, each column is predicted by the reconstructed
column to the left.

The DPCM modes are enabled automatically for blocks with horizontal or
vertical prediction mode, and 1D transform types (ext-tx).

Change-Id: I133ab6b537fa24a6e314ee1ef1d2fe9bd9d56c13