[x265] [PATCH 09 of 10 RFC] docs: document the current state of --limit-refs

[Steve Borho]

# HG changeset patch
# User Steve Borho <steve at borho.org>
# Date 1426555173 18000
#      Mon Mar 16 20:19:33 2015 -0500
# Node ID c11e38ce9d8d55cfed8133a966c3ed58543d5721
# Parent  ab10ce38456cd51ccf63e1934ae648fe3d407252
docs: document the current state of --limit-refs

diff -r ab10ce38456c -r c11e38ce9d8d doc/reST/cli.rst
--- a/doc/reST/cli.rst	Mon Mar 16 20:19:33 2015 -0500
+++ b/doc/reST/cli.rst	Mon Mar 16 20:19:33 2015 -0500
@@ -540,6 +540,31 @@
 	be consistent for all of them since the encoder configures several
 	key global data structures based on this range.
 
+.. option:: --limit-refs <0|1|2|3>
+
+	When set to X265_REF_LIMIT_DEPTH (1) x265 will limit the references
+	analyzed at the current depth based on the references used to code
+	the 4 sub-blocks at the next depth.  For example, a 16x16 CU will
+	only use the references used to code its four 8x8 CUs.
+
+	When set to X265_REF_LIMIT_CU (2), the rectangular and asymmetrical
+	partitions will only use references selected by the 2Nx2N motion
+	search (including at the lowest depth which is otherwise unaffected
+	by the depth limit).
+
+	The two flags may be combined such that the 2Nx2N motion search at
+	each depth will only use references from the split CUs and then the
+	other motion searches at that depth will only use the reference(s)
+	selected by 2Nx2N. Combined they can reduce the number of motion
+	searches by as much as 80%.
+
+	You can often increase the number of references you are using
+	(within your decoder requirement level limits) if you enable one or
+	both of thes flags.
+
+	This feature is EXPERIMENTAL and currently only functional at RD
+	levels 5 and 6
+
 .. option:: --rect, --no-rect
 
 	Enable analysis of rectangular motion partitions Nx2N and 2NxN