commit 5daef90efc4613efd7e7ee80ba4e1ecf9a57a966
author Pengchong Jin <pengchong@google.com> Tue Jun 03 17:16:00 2014 -0700
committer Pengchong Jin <pengchong@google.com> Thu Jun 12 08:55:52 2014 -0700
tree f6c020272592c416abea556f9a40a6cccf5a9d76
parent 0c4a4225ec91d4db1d3b9e0b2b919ebeec60ec57

skip un-neccessary motion search in the first pass

This patch allows the encoder to skip the
un-neccessary motion search in the first pass. It
calculates the error of the zero motion vector using
the last source frame as reference and skips the
further motion search in the first pass if the error
is small.

The encoding speedup of the first pass for slideshow
videos is over 30%. Borg test shows the overall PSNR
performance remain approximately the same (derf -0.009,
hd 0.387, yt 0.021, stdhd 0.065). Individual clips may
have either PSNR gain or loss. The worst PSNR perfomance
is from yt set, with a PSNR loss of -1.1.

Change-Id: I08b2ab110b695e4689573b2567fa531b6457616e