Since I upgraded my N810 to diablo, I can sometimes hear repeated crackling when playing ogg files with mplayer 1.0rc1-maemo.29.n8x0 and using traditional headsets (no bluetooth). I never had such a problem on chinook. Now, I don't really know what the cause is because the mplayer version is newer and I now have an 8-GB external card. Has anyone had a similar problem?
Note that the load average is about 0.4 (however, when I run it, top doesn't report any process using more than 1% CPU time -- except itself).
Also, I did some experiments. Whether the ogg file is on the internal 2-GB card or on the 8-GB card doesn't matter (I get the same behavior). Whether wifi is on or not and whether the touch screen and keys are locked don't matter either. But it seems that crackling almost only occurs when the screen has switched off (it can also occur at some other occasions, but this is much less noticeable and annoying).