[MPlayer-users] iMovie encoded h264, mplayer says "first frame is no keyframe"

[Towncat]

I encoded some home videos with iMovie under Mac OSX. I used the "Export
using QuickTime" feature, Movie to MPEG-4, "video format" H.264, bitrate
2000, framerate 25, keyframe: automatic (btw., what would be a reasonable
number here?), optimized for CD/DVD-ROM.

The resulting clips play nicely under MacOSX's QuickTime player (what would
you expect...? :-) ), but when I try to play them with mplayer either under
Mac or Linux, I get the error "first frame is no keyframe". The clip is
played, but the first few seconds are garbled.

Is there an option for mplayer playback to avoid this, or maybe an encoding
option in iMovie I might try?

(I also tried the "MPEG-4 Improved" "video format", and that did not cause
the same error ("video format" in iMovie I guess is used to mean "codec").

Thanks,
   tc.