Converting MKV to AVI

[Patrick O'Callaghan]

I occasionally need to convert Matroska videos to a format my
stand-alone player (an LG DVD unit) can play. I don't need to author
DVDs since the player can read from a pendrive via a USB port, but it's
fairly limited in the formats it will accept. Xvid seems to work well so
it's what I tend to use.

The MKV files are for standard NTSC or PAL broadcast TV (not even HD in
most cases, though they could be). I've so far been unsuccessful in
hitting reasonable combination of options for producing a useful result.
I've tried ffmpeg, transcode and mencode, but the resulting videos tend
to have have noticeable blocking artefacts (despite playing with
bitrates) and severe sound synch problems. Here's a random example of
the kind of thing I've been trying:

mencoder example.mkv -oac mp3lame -ovc xvid -xvidencopts bitrate=1000:profile=dxnhtntsc:quant_type=mpeg -vf scale=720:480 -o output.avi

I've also messed a little with the mkv* tools, but they appear to assume
a familiarity with Matroska terminology which I would prefer not to have
to acquire.

<rant>
Part of the problem is that all the above tools are clearly aimed at
people who know what they're doing. Those of us uninterested in a career
in multimedia technology are liable to be completely lost when
struggling with any of the (incomplete and ambiguous) manuals, not to
mention the baroque syntax of the command-line options. Why are there no
"multimedia conversion for dummies" tools in Linux as there are in
Windoze?
</rant>

Anyway, my question is this: does anyone have a useful recipe for this
kind of thing?

And for extra credit: how about converting FLV (Flash video)?

poc