[MPlayer-DOCS] CVS: main/DOCS/xml/en encoding-guide.xml,1.32,1.33

[Guillaume Poirier CVS]

CVS change done by Guillaume Poirier CVS

Update of /cvsroot/mplayer/main/DOCS/xml/en
In directory mail:/var2/tmp/cvs-serv16251/DOCS/xml/en

Modified Files:
	encoding-guide.xml 
Log Message:
Add indicative QP for ASP and AVC codecs


Index: encoding-guide.xml
===================================================================
RCS file: /cvsroot/mplayer/main/DOCS/xml/en/encoding-guide.xml,v
retrieving revision 1.32
retrieving revision 1.33
diff -u -r1.32 -r1.33
--- encoding-guide.xml	20 Oct 2005 13:45:41 -0000	1.32
+++ encoding-guide.xml	27 Nov 2005 19:48:39 -0000	1.33
@@ -1043,6 +1043,9 @@
 <sect3 id="menc-feat-dvd-mpeg4-resolution-bitrate-compute">
 <title>Computing the resolution</title>
 <para>
+  The following steps will guide you to compute the resolution of your
+  encode without taking too much distortion by taking into account several
+  information about the souce video.
   First, you should compute the encoded aspect ratio:
   <systemitem>ARc = (Wc x (ARa / PRdvd )) / Hc</systemitem>
 <itemizedlist>
@@ -1079,17 +1082,30 @@
 </para>
 
 <para>
-  The CQ depends both on the bitrate and the movie resolution.
+  The CQ depends both on the bitrate, the video codec efficiency and the
+  movie resolution.
   In order to raise the CQ, typically you would downscale the movie given that the
   bitrate is computed in function of the target size and the length of the
   movie, which are constant.
-  A CQ below 0.18 usually ends up in a very blocky picture, because there
+  With MPEG-4 ASP codecs such as <systemitem class="library">XviD</systemitem>
+  and <systemitem class="library">libavcodec</systemitem>, a CQ below 0.18
+  usually ends up in a pretty blocky picture, because there
   are not enough bits to code the information of each macroblock (MPEG4, like
   many other codecs, groups pixels by blocks of several pixels to compress the
   image; if there are not enough bits, the edges of those blocks are
   visible).
   It is therefore wise to take a CQ ranging from 0.20 to 0.22 for a 1 CD rip,
-  and 0.26-0.28 for 2 CDs.
+  and 0.26-0.28 for 2 CDs with standard encoding options.
+  More advanced encoding options such as those listed here for
+  <link linkend="menc-feat-mpeg4-lavc-example-settings"><systemitem class="library">libavcodec</systemitem></link>
+  and
+<link linkend="menc-feat-xvid-example-settings"><systemitem class="library">XviD</systemitem></link>
+  should make it possible to get the same quality with CQ ranging from
+  0.18 to 0.20 for 1 CD rip, and 0.24-0.26 for 2 CDs
+  With MPEG-4 ASP codecs such as <systemitem class="library">x264</systemitem>,
+  you can use a CQ ranging from 0.14 to 0.16 with standard encoding options,
+  and should be able to go as low as 0.10 to 0.12 with
+  <link linkend="menc-feat-x264-example-settings"><systemitem class="library">x264</systemitem>'s advanced encoding settings</link>.
 </para>
 
 <para>
@@ -1098,6 +1114,8 @@
   to a movie such as The Matrix, which contains many high-motion scenes.
   On the other hand, it is worthless to raise CQ higher than 0.30 as you would
   be wasting bits without any noticeable quality gain.
+  Also note that as said earlier on this quide, low resolution comparatively
+  need a bigger QP to look good.
 </para>
 </sect3>