[MPlayer-DOCS] CVS: main/DOCS/xml/en mencoder.xml,1.71,1.72
Guillaume Poirier CVS
syncmail at mplayerhq.hu
Thu Jun 23 19:25:56 CEST 2005
CVS change done by Guillaume Poirier CVS
Update of /cvsroot/mplayer/main/DOCS/xml/en
In directory mail:/var2/tmp/cvs-serv13594/en
New codec covered by the encoding guide: XviD
RCS file: /cvsroot/mplayer/main/DOCS/xml/en/mencoder.xml,v
retrieving revision 1.71
retrieving revision 1.72
diff -u -r1.71 -r1.72
--- mencoder.xml 13 Jun 2005 01:06:33 -0000 1.71
+++ mencoder.xml 23 Jun 2005 17:25:53 -0000 1.72
@@ -2438,6 +2438,147 @@
+<title>Encoding with the <systemitem class="library">XviD</systemitem>
+ <systemitem class="library">XviD</systemitem> is a free library for
+ encoding MPEG-4 ASP video streams.
+ Before starting to encode, you need to <link linkend="xvid">
+ set up <application>MEncoder</application> to support it</link>.
+ This guide mainly aims at featuring the same kind of information
+ as x264's encoding guide.
+ Therefore, please begin by reading
+ <link linkend="menc-feat-x264-intro">the first part</link> of that
+<title>What options should I use to get the best results?</title>
+ Please begin by reviewing the
+ <systemitem class="library">XviD</systemitem> section of
+ <application>MPlayer</application>'s man page.
+ This section is intended to be a supplement to the man page.
+ The XviD default settings are already a good tradeoff between
+ speed and quality, therefore you can safely stick to them if
+ the following section puzzles you.
+<title>Encoding options of <systemitem class="library">XviD</systemitem></title>
+ <emphasis role="bold">vhq</emphasis>
+ This setting affects the macroblock decision algorithm, where the
+ higher the setting, the wiser the decision.
+ The default setting may be safely used for every encode, while
+ higher settings always help PSNR but are significantly slower.
+ Please note that a better PSNR does not necessarily mean
+ that the picture will look better, but tells you that it is
+ closer to the original.
+ Turning it off will noticeably speed up encoding; if speed is
+ critical for you, the tradeoff may be worth it.
+ <emphasis role="bold">bvhq</emphasis>
+ This does the same job as vhq, but does it on B-frames.
+ It has a negligible impact on speed, and slightly improves quality
+ (around +0.1dB PSNR).
+ <emphasis role="bold">max_bframes</emphasis>
+ A higher number of consecutive allowed B-frames usually improves
+ compressibility, although it may also lead to more blocking artifacts.
+ The default setting is a good tradeoff between compressibility and
+ quality, but you may increase it up to 3 if you are bitrate-starved.
+ You may also decrease it to 1 or 0 if you are aiming at perfect
+ quality, though in that case you should make sure your
+ target bitrate is high enough to ensure that the encoder does not
+ have to increase quantizers to reach it.
+ <emphasis role="bold">bf_threshold</emphasis>
+ This controls the B-frame sensitivity of the encoder, where a higher
+ value leads to more B-frames being used (and vice versa).
+ This setting is to be used together with <option>max_bframes</option>;
+ if you are bitrate-starved, you should increase both
+ <option>max_bframes</option> and <option>bf_threshold</option>,
+ while you may increase <option>max_bframes</option> and reduce
+ <option>bf_threshold</option> so that the encoder may use more
+ B-frames in places that only <emphasis role="bold">really</emphasis>
+ need them.
+ A low number of <option>max_bframes</option> and a high value of
+ <option>bf_threshold</option> is probably not a wise choice as it
+ will force the encoder to put B-frames in places that would not
+ benefit from them, therefore reducing visual quality.
+ However, if you need to be compatible with standalone players that
+ only support old DivX profiles (which only supports up to 1
+ consecutive B-frame), this would be your only way to
+ increase compressibility through using B-frames.
+ <emphasis role="bold">trellis</emphasis>
+ Optimizes the quantization process to get an optimal tradeoff
+ between PSNR and bitrate, which allows significant bit saving.
+ These bits will in return be spent elsewhere on the video,
+ raising overall visual quality.
+ You should always leave it on as its impact on quality is huge.
+ Even if you are looking for speed, do not disable it until you
+ have turned down <option>vhq</option> and all other more
+ CPU-hungry options to the minimum.
+ <emphasis role="bold">cartoon</emphasis>
+ Designed to better encode cartoon content, and has no impact on
+ speed as it just tunes the mode decision heuristics for this type
+ of content.
+ <emphasis role="bold">me_quality</emphasis>
+ This setting is to control the precision of the motion estimation.
+ The higher <option>me_quality</option>, the more
+ precise the estimation of the original motion will be, and the
+ better the resulting clip will capture the original motion.
+ The default setting is best in all cases;
+ thus it is not recommended to turn it down unless you are
+ really looking for speed, as all the bits saved by a good motion
+ estimation would be spent elsewhere, raising overall quality.
+ Therefore, do not go any lower than 5, and even that only as a last
+ <emphasis role="bold">chroma_me</emphasis>
+ Improves motion estimation by also taking the chroma (color)
+ information into account, whereas <option>me_quality</option>
+ alone only uses luma (grayscale).
+ This slows down encoding by 5-10% but improves visual quality
+ quite a bit by reducing blocking effects.
+ If you are looking for speed, you should disable this option before
+ starting to consider reducing <option>me_quality</option>.
<title>How to deal with telecine and interlacing within NTSC DVDs</title>
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