tree 38cbc4ad00230df8658b830f879031c59e4a6fc1
parent 7a864cc73e22295c9e92ead7f62b70ba47f47e4e
author Sarah Parker <sarahparker@google.com> 1527041207 -0700
committer Sarah Parker <sarahparker@google.com> 1530231714 +0000

Initial encoder implementation for fwd kf

Add encoder implementation to code forward reference
keyframes as a unfiltered altrefs. In this case, the altref source
is placed on the keyframe location determined in firstpass.c.
This frame is first coded as an invisible keyframe which only updates
the altref buffer. All reference buffers are cleared when the keyframe
is finally displayed using cm->show_existing_frame.

This is a preliminary implementation and has not yet made appropriate
changes to the rate control. There also seems to be a bug in some
instances when the keyframes are spread far apart, and seems to be
an issue with the way the postencode_update is being handled. I am
currently working on a fix as a followup.

This patch does not impact results if --enable-fwd-kf is set to 0.

Preliminary Results:
20 encoded frames with kf-max-dist set to 5: -9.47% gain
20 encoded frames with kf-max-dist set to 8: -11.02% gain
20 encoded frames with kf-max-dist set to 10: 1.60%  loss

STATS_CHANGED

Change-Id: I598038162756a473a033e8d1c26715b0429844a3