[MPlayer-DOCS] Re: [MPlayer-dev-eng] A DVD ripping example into docs?

Samuli Kärkkäinen skarkkai at woods.iki.fi
Sun Dec 28 04:21:05 CET 2003 

On Sat, Dec 27, 2003 at 06:14:07PM -0300, Diego Biurrun wrote:
> Sorry for responding this late, the message got blocked because you
> were not subscribed to the mailing list.
> 
> Having something like this in the docs would be very cool.
> Unfortunately I don't know squat about encoding, so I cannot really
> review this.  Once you have a patch ready, please send it to the
> mplayer-docs mailing list.  We'll help you with integrating the patch
> into the docs structure there.

Here's a patch against current CVS. I'm not subscribed to this list
either, if that makes some difference.

--- DOCS/xml/en/mencoder.xml.orig	2003-12-28 05:11:48.000000000 +0200
+++ DOCS/xml/en/mencoder.xml	2003-12-28 05:11:54.000000000 +0200
@@ -569,4 +569,166 @@
 </para>
 </sect1>
 
+<sect1 id="menc-feat-dvd-mpeg4">
+<title>Making a high quality MPEG4 (&quot;DivX&quot;) rip of a DVD movie</title>
+
+<para>
+  Ripping a DVD title into a maximally high quality mpeg4 (DivX) file
+  involves many considerations.  Below is an example of the process when
+  there's no file size goal (other than perhaps fitting the result into 2
+  GB).  The libavcodec codec will be used for the video, and the audio will be
+  copied as is without any changes.
+</para>
+
+<sect2 id="menc-feat-dvd-mpeg4-crop">
+<title>Cropping</title>
+<para>
+  Play the DVD and run a crop detect filter (<option>-vf
+  cropdetect</option>) on it.  This gives you a crop rectangle to use
+  for encoding.  The reason for cropping is that many movies are filmed
+  in a different aspect ratio than standard DVD ratios (16/9 or 4/3),
+  or, for whatever reason, the picture does not properly fill the
+  frame. So you want to crop out the pointless black bars when you rip. 
+  A common aspect is 2.35, which is cinescope.  Most big blockbuster
+  movies have this aspect ratio.
+</para></sect2>
+
+<sect2 id="menc-feat-dvd-mpeg4-quality">
+<title>Quality level</title>
+<para>
+  Next you need to choose the desired quality level.  When there's no
+  need to fit the resulting file on CD's or the like, using constant
+  quantizing aka constant quality is a good choice.  That way each frame
+  is given as much bits as its needs to keep the quality at desired
+  level, but multiple encoding passes are not needed. With
+  libavcodec, you get constant quality by using <option>-lavcopts
+  vqscale=<replaceable>N</replaceable></option>. Using
+  <option>vqscale=3</option> gives you a file that's usually below 2
+  GB, depending mainly on the movie length and video noisiness (the
+  more noise, the harder it is to compress.)
+</para></sect2>
+
+<sect2 id="menc-feat-dvd-mpeg4-2gb">
+<title>Files over 2 GB</title>
+<para> 
+  When you're done encoding using constant quality, you may find the
+  resulting file is over 2 GB. As of this writing, 28 Dec 2003, in
+  order to view larger than 2 GB files, mplayer CVS version requires
+  you to clumsily create index into a separate file using
+  <option>-saveidx</option> and <option>-loadidx</option> options. 
+  Slightly older versions, such as 0.92, are even clumsier, and require
+  you to use -forceidx upon every viewing with over 2 GB avis. If this
+  bothers you, you may want to keep the file size below 2 GB.
+  
+  </para><para>
+  
+  To this end, you have two choices.  You can try encoding again using
+  <option>vqscale=4</option> and see if both the resulting file size
+  and picture quality are acceptable.  You can also use 2 pass encoding
+  as explained elsewhere in this manual.  As you will be copying the
+  audio track as is and hance know its bitrate, and you know the
+  running time of the movie, you can compute the required bitrate to
+  give to <option>-lavcopts
+  vbitrate=<replaceable>bitrate</replaceable></option> option without
+  using 3 pass encoding.
+</para></sect2>
+
+<sect2 id="menc-feat-dvd-mpeg4-deinterlacing">
+<title>Deinterlacing</title>
+<para> 
+  If the movie is interlaced, you may want to deinterlace it as part of
+  the ripping.  It's debatable whether deinterlacing should be done at
+  this stage.  The benefit is that deinterlacing when converting to
+  mpeg4 makes compession better, and viewing easier and less CPU
+  intensive on computer monitor as no deinterlacing is required at that
+  time.
+  
+  </para><para>
+  
+  Deinterlacing at ripping stage is an idea whose goodness depends on
+  the DVD.  If the DVD is made from film, which was shot at 24 fps, you
+  can as well deinterlace while ripping since as far as I can see,
+  nothing will be lost anyway.  If however the original was 50/60 fps
+  video, converting into deinterlaced into 23.976/25 fps video will
+  lose information.  If you do decide to interlace, you can further
+  experiment with different deinterlacing filters.  See
+  <ulink url="http://www.wieser-web.de/MPlayer/">http://www.wieser-web.de/MPlayer/</ulink> for examples.
+  I currently use <option>-vf pp=fd</option>.
+
+  </para><para>
+
+  If you're both cropping and deinterlacing, deinterlace
+  <emphasis>before</emphasis> cropping. Actually, this is not necessary
+  if the crop offset is vertically a multiple of 2 pixel. However with
+  some other filters like dering you should always crop last, so it's a
+  good habit to crop in the last stage.
+</para></sect2>
+
+<sect2 id="menc-feat-dvd-mpeg4-telecine">
+<title>Inverse telecine</title>
+<para> 
+  If you're ripping a PAL DVD, which is 25 fps, you don't need to think
+  of the fps. Just use the 25 fps. NTSC DVDs on the other hand are
+  29.97 fps (often rounded to 30 fps, but that's not what they are). 
+  If the movie was shot for TV, you again don't need to touch the fps. 
+  But if the movie was shot on film, and hence at (exactly) 24 fps,
+  then it has been converted into 29.97 fps when making the DVD. That
+  conversion where 12 fields are added to each 24 frames of film is
+  called telecine. For more info about telecine, see a <ulink
+  url="http://www.google.com/search?q=telecine+field+23.976">Google
+  search for "telecine field 23.976"</ulink>.
+
+  </para><para>
+
+  In case you have such telecined DVD, you will want to do inverse
+  telecine, that is convert the movie to 23.976 (29.97*4/5).  Otherwise
+  camera panning will look jerky and awful. I use <option>-ofps
+  23.976</option> for this. Anything that is shown on theatres is shot
+  in film and needs inverse telecine, and TV shows like Friends don't.
+</para></sect2>
+
+<sect2 id="menc-feat-dvd-mpeg4-scaling">
+<title>Scaling and aspect ratio</title>
+<para> 
+  For best quality, don't scale the movie while ripping. Scaling causes
+  artifacts and makes the file larger. Pixels in DVD movies aren't
+  square, so DVD movies include info about the correct aspect ratio. 
+  It's possible to store the aspect ratio also in the mpeg4 header of
+  the output file. Most video players ignore this info, but mplayer
+  doesn't.  Hence if you're only going to use mplayer for viewing the
+  output file, you don't need to scale the movie but just give option
+  <option>-lavcopts autoaspect</option> to mencoder and things will
+  then work automagically right. If you must scale the movie, be
+  careful about getting the size right especially if you do cropping.
+</para></sect2>
+
+<sect2 id="menc-feat-dvd-mpeg4-sumup">
+<title>Summing it up</title>
+<para> 
+  All of the above put together, a suitable encoding command might be
+
+  <screen>
+mencoder -dvd 1 -aid 128 -oac copy -ovc lavc -lavcopts vcodec=mpeg4:vqscale=3:vhq:v4mv:trell:autoaspect \
+  -ofps 23.976 -vf crop=720:364:0:56 -o Harry_Potter_2.avi
+  </screen>
+
+  Here <option>-dvd 1</option> gives the DVD title to rip. Option
+  <option>-aid 128</option> says to use audio track 128, and
+  <option>-oac copy</option> to copy it as is. You'll have to use
+  mplayer to find out the right for these.
+  
+  </para><para>
+  
+  Options <option>vhq:v4mv:trell</option> for
+  <option>-lavcopts</option> improve quality versus bitrate, but make
+  encoding take longer. Especially <option>trell</option> slows
+  encoding down but also increases quality visibly. If you want to
+  deinterlace, add a <option>pp</option> filter to
+  <option>-vf</option>, for example <option>-vf
+  pp=fd,crop=720:364:0:56</option> (in that order).  If you don't need
+  inverse telecine, leave out the <option>-ofps 23.976</option>.
+</para></sect2>
+
+</sect1>
+
 </chapter>

-- 
  Samuli Kärkkäinen                   |\      _,,,---,,_
 skarkkai at woods.iki.fi ---------ZZZzz /,`.-'`'    -.  ;-;;,_------
http://www.woods.iki.fi              |,4-  ) )-,_. ,\ (  `'-'
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