Could you please test '-ao sdl' in mplayer_1.0rc1-maemo.25 setting various audio delay values (using -delay option)? The actual value of audio delay that is needed for proper lipsync for various types of audio (different sampling rate, mono/stereo) is interesting.

I strongly suspect that we can't rely on audio delay reported by esd at all. The reason why previous build worked, may be because several bugs negated each other

If we assume that the audio delay is constant, we just need to measure this constant.

Right now you can try editing '/home/user/.mplayer/config' file and add the following lines:
ao=sdl
delay=0.2

Actual delay value should be probably somewhere in the range between 0.10 and 0.30, please report if you get some good results.