One problem with mencoder is the lack of a way to interleave the AVI you create. So you have to turn right around and use AVIdemux to create the final interleaved AVI so you can seek in it using mplayer. I expect this to be the source of most of the A-V desync issues announced on this list when seeking.

you mean that mencoder created avi files aren't interleaved?

Let me rephrase this, it's too confusing. Actually I'm not 100% sure whether mencoder interleaves at all or interleaves improperly to maintain A-V sync on playback. But, I can only get good A-V sync of AVIdemux AVI's when seeking in mplayer. And I know AVIdemux is using interleave every frame. Shaun