Denis Papathanasiou

I first used LaTeX while an intern at a very old-school software company that ran only unix workstations.

When I needed to write a letter (that had to be printed on paper and signed, for some bureaucratic task), I was told "try this".

At first, the idea of writing in markup, then compiling it to get final document seemed strange, but I quickly came to love using it. Pretty soon, anything that I used to do in Word I would do in LaTeX instead.

I got away from it entirely these last few years, as most things that used to require a printed letter or memo have succumbed to email, web forms, and the like.

But recently I had the need again, for a new project, and thought: why not?

The only difference now is that instead of printing to paper, I would be sending pdf files by email.

Fortunately, the Ghostscript ps2pdf utility makes that simple, and it was already installed on my computer.

Likewise, LaTeX itself was already installed and available, thanks to the TeX Live package.

The only remaining annoyance was all the commands I needed to run for each document:

$ latex test.tex
$ dvips test.dvi
$ ps2pdf test.ps

and, to clean-up all the intermediate files those commands generated:

$ rm test.aux test.dvi test.log test.ps

So I wrote this latex2pdf shell script:

#!/bin/sh

if [ $# -ne 1 ]
then
    echo "usage: latex2pdf.sh [file(.tex)]"
else
    # split $1 on / to get the path and filename
    path=`echo ${1%/*}`
    file=`echo ${1##*/}`
    if [ $path = $file ]
    then
        path=`pwd`
    fi

    # check if the file already has the .tex ext
    suffix=`echo $file | grep ".tex$" | wc -l`
    if [ $suffix -eq 0 ]
    then
        f=`echo "$file.tex"`
    else
        f=`echo "$file"`
    fi

    # define the filename base string w/o the .tex ext
    # (what the .aux, .dvi., .ps, .log files will be named)
    s=`echo "$f" | sed -e 's/\.tex$//'`

    # compile the .tex file and convert to pdf
    latex "$path/$f"
    dvips "$s.dvi"
    ps2pdf "$s.ps"
    rm -f "$s.aux"
    rm -f "$s.dvi"
    rm -f "$s.log"
    rm -f "$s.ps"
fi

Now, with a single command, I can build and view the result immediately:

$ ./latex2pdf.sh test.tex; xpdf test.pdf &

Who needs WYSIWYG?

One of the nice things about MythTV is that it lets me save any broadcast as an unencrypted, DRM-free mpeg file.

I recently found out how to use MEncoder to split and trim those mpeg files into single or multiple clips.

MEncoder is a good tool to use because it’s free (as in both freedom and beer), and runs on all major platforms (there are even pre-built binaries for Mac OSX).

MEncoder has two command line options, -ss and -endpos, which let you define the start or end position of the clip you want to extract.

Unfortunately, the default command doesn’t work with mpeg files.

The work-around is to convert the mpeg file to avi format first:

$ mencoder original.mpeg -ovc lavc -oac lavc -o original.avi

Then, create a copy starting or ending at a given point in time, defined as hour:minute:second using either the -ss or -endpos options.

For example, to extract a clip from the 17 minute 50 second mark to the 57 minute 47 second mark from a one-hour file, these two commands will do the trick:

$ mencoder -ss 00:17:50 -oac copy -ovc copy original.avi -o clip_start.avi
$ mencoder -endpos 00:39:57 -oac copy -ovc copy clip_start.avi -o clip.avi

Note that the -endpos was recalculated for the second command as 39:57, not 57:47.

That’s because the clip_start.avi file is 17 minutes and 50 seconds shorter than the original, and so we need to recalculate the clip end position in terms of the new length.

The file clip.avi contains the clip from 17:50 to 57:47 extracted from the original file, and we can discard the intermediate clip_start.avi file.

It takes two commands because MEncoder seems to ignore the second -ss or -endpos option it finds, and uses just the first one.

It would be nice if it would just let us do this instead:

$ mencoder -ss 00:17:50 -endpos 00:57:47 -oac copy -ovc copy original.avi -o clip.avi