> However, all attempt to use the webm container have led to crashes for
> me. If you have a working build, would you share it?
>
This may happen when attempting two pass as mencoder's use of lavf
differs from ffmpeg in that it will call write_trailers on the muxer
even if no data has been written (which is true in the first pass).
Using the default avi muxer in the first pass with /dev/null as the
file will avoid this.