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<H2><A NAME="encoding">2.4 Encoding with MEncoder</A></H2>
<P>For the complete list of available MEncoder options and examples, please see
the man page.</P>
<H3><A NAME="2pass">2.4.1 Encoding 2 or 3-pass DivX4</A></H3>
<P><U><B>2-pass encoding:</B></U> the name comes from the fact that this method
encodes the file <I>twice</I>. The first encoding (dubbed <I>pass</I>)
creates some temporary files (*.log) with a size of few megabytes, do not
delete them yet (you can delete the AVI). In the second pass, the 2-pass
output file is created, using the bitrate data from the temporary files. The
resulting file will have much better image quality. If this is the first time
you heard about this, you should consult some guides available on the
Net.</P>
<P>This example shows how to encode a DVD to a 2-pass DivX4 AVI. Just two
commands are needed:<BR>
<CODE> rm frameno.avi</CODE> - remove this file, which
can come from a previous 3-pass encoding (it interferes with current
one)<BR>
<CODE> mencoder -dvd 2 -ovc lavc -lavcopts
vcodec=mpeg4:vpass=1 -oac copy -o movie.avi<BR>
mencoder -dvd 2 -ovc lavc -lavcopts
vcodec=mpeg4:vpass=2 -oac copy -o movie.avi</CODE></P>
<P><U><B>3-pass encoding:</B></U> this is an extension of 2-pass encoding,
where the audio encoding takes place in a separate pass. This method enables
estimation of recommended video bitrate in order to fit on a CD. Also, the
audio is encoded only once, unlike in 2-pass mode. The schematics:</P>
<OL>
<LI>Remove conflicting temporary file:
<P><CODE>rm frameno.avi</CODE></P></LI>
<LI>First pass:
<P><CODE>mencoder <file/DVD> -ovc frameno -oac mp3lame -lameopts vbr=3 -o frameno.avi</CODE></P>
<P>An audio-only avi file will be created, containing
<B>only</B> the requested audio stream. Don't forget <CODE>-lameopts</CODE>,
if you need to set it. If you were encoding a long movie, MEncoder
prints the recommended bitrate values for 650Mb, 700Mb, and 800Mb
destination sizes, after this pass finishes.</P></LI>
<LI>Second pass:
<P><CODE>mencoder <file/DVD> -oac copy
-ovc lavc -lavcopts vcodec=mpeg4:vpass=1:vbitrate=<bitrate></CODE></P>
<P>Alias the first pass of DivX4 video encoding.
Optionally specify the video bitrate MEncoder printed at the end of
the previous pass.</P></LI>
<LI>Third pass:
<P><CODE>mencoder <file/DVD> -oac copy
-ovc lavc -lavcopts vcodec=mpeg4:vpass=2:vbitrate=<bitrate></CODE></P>
<P>Alias the second pass of DivX4 video encoding.
Optionally specify the video bitrate MEncoder printed at the end of
the previous pass. In this pass, audio from <CODE>frameno.avi</CODE> will
be inserted into the destination file.. and it's all ready!</P></LI>
</OL>
<H4>Example for 3-pass encoding:</H4>
<P><CODE> rm frameno.avi</CODE> - remove this file,
which can come from a previous 3-pass encoding (it interferes with current
one)<BR>
<CODE> mencoder -dvd 2 -ovc frameno
-o frameno.avi -oac mp3lame -lameopts vbr=3<BR>
mencoder -dvd 2 -ovc lavc
-lavcopts vcodec=mpeg4:vpass=1 -oac copy -o movie.avi<BR>
mencoder -dvd 2 -ovc lavc
-lavcopts vcodec=mpeg4:vpass=2 -oac copy -o movie.avi</CODE></P>
<H3><A NAME="rescaling">2.4.2 Rescaling movies</A></H3>
<P>Often the need to resize movie images' size emerges. Its reasons can be
many: decreasing file size, network bandwidth, etc. Most people
even do rescaling when converting DVDs or SVCDs to DivX AVI. <B>This is bad.</B>
Instead of even you doing so, read the <A HREF="#aspect">Preserving
aspect ratio</A> section.</P>
<P>The scaling process is handled by the <I>'scale'</I> video filter:
<CODE>-vop scale=widht:height</CODE>. Its quality can be set with the
<CODE>-sws</CODE> option. If it's not specified, MEncoder will use 0:
fast bilinear.</P>
<H5>Usage:</H5>
<P><CODE> mencoder input.mpg -ovc lavc -lavcopts
vcodec=mpeg4 -vop scale=640:480 -oac copy -o
output.avi</CODE></P>
<H3><A NAME="copying">2.4.3 Stream copying</A></H3>
<P>MEncoder can handle input streams in two ways: <B>encode</B> or
<B>copy</B> them. This section is about <B>copying</B>.</P>
<UL>
<LI><B>Video stream</B> (option <CODE>-ovc copy</CODE>): nice stuff can be
done :)<BR>
Like, putting (not converting) FLI or VIVO or MPEG1 video into
an AVI file. Of course only MPlayer can play such files :) And it
probably has no real life value at all. Rationally: video stream copying
can be useful for example when only the audio stream has to be encoded
(like, uncompressed PCM to MP3).</LI>
<LI><B>Audio stream</B> (option <CODE>-oac copy</CODE>): straightforward.
It is possible to take an external audio file (MP3, Vorbis) and mux it
into the output stream. Use the <CODE>-audiofile <filename></CODE>
option for this.</LI>
</UL>
<H3><A NAME="fixing">2.4.4 Fixing AVIs with broken index or interleaving</A></H3>
<P>Easiest thing. We simply copy the video and audio streams, and
MEncoder generates the index. Of course this cannot fix possible bugs
in the video and/or audio streams. It also fixes files with broken
interleaving, thus the <CODE>-ni</CODE> option won't be needed for them
anymore.</P>
<P>Command: <CODE>mencoder -idx input.avi -ovc copy -oac copy -o output.avi</CODE></P>
<H3><A NAME="libavcodec">2.4.5 Encoding with the libavcodec codec family</A></H3>
<P><A HREF="codecs.html#libavcodec">libavcodec</A> provides simple encoding to a
lot of interesting video and audio formats (currently its audio codecs are
unsupported). You can encode to the following codecs:</P>
<UL>
<LI>mjpeg - Motion JPEG</LI>
<LI>h263 - H263</LI>
<LI>h263p - H263 Plus</LI>
<LI>mpeg4 - DivX4</LI>
<LI>msmpeg4 - the old DivX</LI>
<LI>msmpeg4v2 - Micro$oft MPEG4 V2 (DivX alias MP43 predecessor)</LI>
<LI>rv10 - an old RealVideo codec</LI>
<LI>mpeg1video - MPEG1 video :)</LI>
</UL>
<P>The first column contains the codec names that should be passed after the
<CODE>vcodec</CODE> config, like: <CODE>-lavcopts vcodec=msmpeg4</CODE></P>
<P>An example, with MJPEG compression:<BR>
<CODE> mencoder -dvd 2 -o title2.avi -ovc lavc
-lavcopts vcodec=mjpeg -oac copy</CODE></P>
<H3><A NAME="image_files">2.4.6 Encoding from multiple input image files (JPEGs, PNGs or TGAs)</A></H3>
<P>MEncoder is capable of creating movies from one or more JPEG, PNG or TGA
files. With simple framecopy it can create MJPEG (Motion JPEG), MPNG
(Motion PNG) or MTGA (Motion TGA) files.</P>
Explanation of the process:
<OL>
<LI>MEncoder <I>decodes</I> the input image(s) with
<CODE>libjpeg</CODE> (when decoding PNGs, it will use <B>libpng</B>).</LI>
<LI>MEncoder then feeds the decoded image to the chosen video compressor
(DivX4, Xvid, ffmpeg msmpeg4, etc...). Watch for the PNG decoder, as
currently it can output only to RGB formats, thus can't be used with codecs
that require YUV as input, like DivX4 or ffmpeg's msmpeg4.</LI>
</OL>
<H4>Examples</H4>
<P>The explanation of the <CODE>-mf</CODE> option can be found below in the
global <A HREF="#options">Options</A> section and in the man page.</P>
<P><I>Creating a DivX4 file from all the JPEG files in the current dir:</I><BR>
<CODE>mencoder \*.jpg -mf on:w=800:h=600:fps=25 -ovc divx4
-o output.avi</CODE></P>
<P><I>Creating a DivX4 file from some JPEG files in the current dir:</I><BR>
<CODE>mencoder frame001.jpg,frame002.jpg -mf on:w=800:h=600:fps=25
-ovc divx4 -o output.avi</CODE></P>
<P><I>Creating a Motion JPEG (MJPEG) file from all the JPEG files in the current dir:</I><BR>
<CODE>mencoder \*.jpg -mf on:w=800:h=600:fps=25 -ovc copy
-o output.avi</CODE></P>
<P><I>Creating an uncompressed file from all the PNG files in the current dir:</I><BR>
<CODE>mencoder \*.png -mf on:w=800:h=600:fps=25:type=png -ovc raw
-o output.avi</CODE></P>
<P><I>Creating a Motion PNG (MPNG) file from all the PNG files in the current dir:</I><BR>
<CODE>mencoder \*.png -mf on:w=800:h=600:fps=25:type=png -ovc copy
-o output.avi</CODE></P>
<P><I>Creating a Motion TGA (MTGA) file from all the TGA files in the current dir:</I><BR>
<CODE>mencoder \*.tga -mf on:w=800:h=600:fps=25:type=tga -ovc copy
-o output.avi</CODE></P>
<H3><A NAME="vobsub">2.4.7 Extracting DVD subtitles to a Vobsub file</A></H3>
<P>MEncoder is capable of extracting subtitles from a DVD into
Vobsub fomat files. They consist of a pair of files ending in
<CODE>.idx</CODE> and <CODE>.sub</CODE> and are usually packaged in a single
<CODE>.rar</CODE> archive. MPlayer can play these with the
<CODE>-vobsub</CODE> and <CODE>-vobsubid</CODE> options.</P>
<P>You specify the basename (i.e without the <CODE>.idx</CODE> or
<CODE>.sub</CODE> extension) of the output files with <CODE>-vobsubout</CODE>
and the index for this subtitle in the resulting files with
<CODE>-vobsuboutindex</CODE>.</P>
<P>If the input is not from a DVD you should use <CODE>-ifo</CODE> to
indicate the <CODE>.ifo</CODE> file needed to construct the resulting
<CODE>.idx</CODE> file.</P>
<P>If the input is not from a DVD and you do not have the <CODE>.ifo</CODE>
file you will need to use the <CODE>-vobsubid</CODE> option to let it know
what language id to put in the <CODE>.idx</CODE> file.</P>
<P>Each run will append the running subtitle if the <CODE>.idx</CODE> and
<CODE>.sub</CODE> files already exist. So you should remove any before
starting.</P>
<H4>Examples</H4>
<P><I>Copying two subtitles from a DVD while doing 3-pass encoding</I><BR>
<CODE>rm subtitles.idx subtitles.sub</CODE><BR>
<CODE>mencoder -dvd 1 -vobsubout subtitles -vobsuboutindex 0
-sid 2 -o frameno.avi -ovc frameno -oac mp3lame -lameopts vbr=3</CODE><BR>
<CODE>mencoder -dvd 1 -oac copy -ovc divx4 -divx4opts pass=1</CODE><BR>
<CODE>mencoder -dvd 1 -oac copy -ovc divx4 -divx4opts pass=2 -vobsubout
subtitles -vobsuboutindex 1 -sid 5</CODE></P>
<P><I>Copying a french subtitle from an MPEG file</I><BR>
<CODE>rm subtitles.idx subtitles.sub</CODE><BR>
<CODE>mencoder movie.mpg -ifo movie.ifo -vobsubout subtitles
-vobsuboutindex 0 -vobsuboutid fr -sid 1</CODE></P>
<H3><A NAME="aspect">2.4.8 Preserving aspect ratio</A></H3>
<P>DVDs and SVCDs (i.e. MPEG1/2) files contain an aspect ratio value,
which describes how should the player scale the video stream, so humans
won't have egg heads (ex.: 480x480 + 4:3 = 640x480). However when encoding
to AVI (DivX) files, you have be aware that AVI headers don't store this
value. Rescaling the movie is disgusting and time consuming, there
must be a better feature!</P>
<P>There is.</P>
<P>MPEG4 has an unique feature: the video stream can contain
its needed aspect ratio. Yes, just like MPEG1/2 files (DVD, SVCD).
Regretfully, there are <U>no</U> video players outside which support this
attribute. Except MPlayer.</P>
<P>This feature can be used only with <B>libavcodec</B>'s <CODE>mpeg4</CODE>
codec. Keep in mind: although MPlayer will correctly play the created file,
other players will use the wrong aspect ratio.</P>
<P>You seriously should crop the black bands over and below the movie image.
See the manpage about the usage of the <CODE>cropdetect</CODE> and
<CODE>crop</CODE> filters.</P>
<H5>Usage:</H5>
<P><CODE>$ mencoder sample-svcd.mpg -ovc lavc -lavcopts
vcodec=mpeg4:aspect=16.0/9.0 -vop crop=714:548:0:14 -oac copy -o output.avi</CODE></P>
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