I am waiting to hear from at least a couple more people on various different tablets to make sure "my patch" (the same thing you duplicated already in about 10 seconds, just a define/undefine) is effective in different scenarios / all tablets. I've been away for a few days, so I haven't found anything else yet, but I am still examining the code and experimenting.

Edit: I've done a lot of testing, and at this point it's fairly safe to say that the problem with alsa playback is not mplayer's fault. ALSA completely ignores any attempts to configure the default device using functions like "snd_pcm_hw_params_set_period_size_near", etc. My initial thought is that this is the result of a "feature" designed to keep the values inside certain hardware boundaries... If that is the case, possibly the boundaries are being detected wrong by ALSA? This is pure conjecture at the moment, but I will be checking out ALSA in the morning to see what I can find out.