Mobile Smith

I wrote this for a friend as suggestions for a specific video, but the advice is generic. (Also, see my previous post on MPEG4 for an explanation of MPEG4 "Parts").

I spoke with the person who advocated 3ivx to me (due
to quality) and he has not tried DivX or XviD at all,
so any of the three encoders would probably work as
long as you are creating "MPEG4 Part 2"-compatible
encodings.

If I calculate correctly, 70MB for 30 minutes is
roughly 311 kilobits per second. That's getting close
to the limit of decent quality (I think) for 320x240
video, though you are using 180 vertical which should
allow you to reduce bitrate at the same quality of
320x240 by 30%. After verifying 5 frames per second
and key frames every 10 seconds, and 320 x 180, you
may want to crank down the bitrate to 200 kbps (file
size would be 45MB), or 250kbps (file size of 56MB).
With your frame size of 320x180, you may even get okay
quality out of 150kbps.

Once you determine the lower limit of decency
(bitrate-wise), then you can start using that for
everything. You'll probably want to always select
multiple passes and, if possible, variable bit rate.
Then if you run into video with fast movement, or a
lot of movement for more than 10 seconds (the keyframe
spacing), you'll want to verify the quality
post-encoding.