[x265] [PATCH 1 of 3] doc: update tune grain documentation
Min Chen
chenm003 at 163.com
Tue Apr 12 19:31:00 CEST 2016
# HG changeset patch
# User Deepthi Nandakumar <deepthi at multicorewareinc.com>
# Date 1460210548 -19800
# Node ID 40afead3177d7c128066334bfe075042388e86b0
# Parent 31a417fa69ce37a76e41c203a017686fe7f73877
doc: update tune grain documentation
diff -r 31a417fa69ce -r 40afead3177d doc/reST/presets.rst
--- a/doc/reST/presets.rst Sat Apr 09 19:06:56 2016 +0530
+++ b/doc/reST/presets.rst Sat Apr 09 19:32:28 2016 +0530
@@ -121,29 +121,22 @@
~~~~~~~~~~~~~~~~~~~~
:option:`--tune` *grain* tries to improve the retention of film grain in
-the reconstructed output. It disables rate distortion optimizations in
-quantization, and increases the default psy-rd.
+the reconstructed output. Varying the quantization parameter within and
+across frames causes grain strobing (uneven distribution of grain), which
+is visually distracting. :option: `--tune` *grain* severely dials down
+algorithms that vary the quantization parameter.
- * :option:`--psy-rd` 0.5
- * :option:`--rdoq-level` 0
- * :option:`--psy-rdoq` 0
+ * :option:`--aq-mode` 0
+ * :option:`--cu-tree` 0
+ * :option:`--ip-factor` 1.1
+ * :option:`--pb-factor` 1.0
+ * :option:`--qp-step` 1
-It lowers the strength of adaptive quantization, so residual energy can
-be more evenly distributed across the (noisy) picture:
-
- * :option:`--aq-strength` 0.3
-
-And it similarly tunes rate control to prevent the slice QP from
-swinging too wildly from frame to frame:
-
- * :option:`--ipratio` 1.1
- * :option:`--pbratio` 1.1
- * :option:`--qcomp` 0.8
-
-And lastly it reduces the strength of deblocking to prevent grain being
-blurred on block boundaries:
-
- * :option:`--deblock` -2
+It also enables a specialised ratecontrol algorithm :option:`--rc-grain`
+that strictly minimises QP fluctuations across frames, while still allowing
+the encoder to hit bitrate targets and VBV buffer limits (with a slightly
+higher margin of error than normal). It is highly recommended that this
+algorithm is used only through the :option:`--tune` *grain* feature.
Fast Decode
~~~~~~~~~~~
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