[x265] [PATCH] doc: updated rst doc about param ssim-rd

[ashok at multicorewareinc.com]

# HG changeset patch
# User Ashok Kumar Mishra <ashok at multicorewareinc.com>
# Date 1483532305 -19800
#      Wed Jan 04 17:48:25 2017 +0530
# Node ID c350c4d19b577b46d5be8141383695c9726f59f9
# Parent  255a921f8f894b4cd23dc00a5fef97b9289c9fad
doc: updated rst doc about param ssim-rd

diff -r 255a921f8f89 -r c350c4d19b57 doc/reST/cli.rst
--- a/doc/reST/cli.rst	Wed Jan 04 15:40:08 2017 +0530
+++ b/doc/reST/cli.rst	Wed Jan 04 17:48:25 2017 +0530
@@ -944,6 +944,16 @@
 	maximum TU size is smaller than the CU size then transform QT begins 
 	at the depth of the max-tu-size. Default: 32.
 
+.. option:: --ssim-rd, --no-ssim-rd
+
+    Enable/Disable SSIM RDO. SSIM is a better perceptual quality assessment
+    method as compared to MSE. SSIM based RDO calculation is based on residual
+    divisive normalization scheme. This normalization is consistent with the 
+    luminance and contrast masking effect of Human Visual System. It is used
+    for mode selection during analysis of CTUs and can achieve significant 
+    gain in terms of objective quality metrics SSIM and PSNR. It only has effect
+    on presets which use RDO-based mode decisions (:option:`--rd` 3 and above).
+
 Temporal / motion search options
 ================================