I'm using mencoder (version 1.1-4.8 on Ubuntu 14.04) to encode various avi, mp4 and mkv files into smaller .avi files with srt subtitles "burned in" (to view in a portable dvd player that has very limited format support). It usually works great, except with some mkv files that already include one or more subtitle tracks. In those cases the output file displays the original subtitle lines for around half a second and then switches to the text from the srt file I provided, repeating this behavior for every piece of dialog. I use spanish language .srt files, and the mkv files usually have english subtitles produced from closed-captioning, so the quick switch (nothing on screen -> english dialogue -> Spanish dialogue) can be extremely confusing.
I can't find a way of telling mencoder to ignore any subtitles that come with the mkv file and use only the srt file I provided, so I wonder if anyone here had a similar problem and could find a solution.
for reference, I'm doing 2-pass conversion and these are the parameters I use for the second pass:
original_file.mkv -oac mp3lame -ovc xvid -vf scale -zoom -xy 720 -xvidencopts bitrate=2500:me_quality=6:threads=2:pass=2 -noautosub -forcedsubsonly -sub subtitles.srt -subfont-text-scale 2.5 -subcp latin1 -subpos 85 -passlogfile /tmp/logfile -o output.avi -quiet