I just registered to be able to respond, I have been following this thead (and the now closed libstagefright development thread) for months.
I use an MK808B with Finless 1.7 ROM (android 4.1 which works better for me than 4.2, specially WiFi), libstagefright.so patch from the Rockchip developer and the advancedsettings.xml file to enable it. I use a recent XBMC nighty (see log link below) and found the following which has not been reported before; this behaviour has been present since the first version with the working libstagefright.so and every nighty I used since August 1st (used 7 or 8 different samples or so).
Playing a 1080p MKV movie works fine and smooth, when I press 'o' to see the diagnostics I see 0 drops. That is, for the first 30 minuts or so (although there are still some sporadic drops, especially when there are user actions). After this time I get interruptions where XBMC drops frames frequently.
My first thought was overheating, so I replaced the stock cooler whith a bigger copper cooler, in the end even added a small fan. Now the CPU stays really cool, but still the dropouts start at about 30 minutes. So now I'm suspecting it was not a heat problem at all and could be a software problem afterall.
Does this happen to others as well? The first 30 minutes it is just as it should be, no (or little) drops and smooth, so you can only reproduce it after watching 30 minutes at full HD.
This happend with all 1080p MKV movies I tried, so it is not an error in one specific film. The data is read over USB from an external disk, no network used. A 3 hour 1080p movie can be viewed completely using MX Player Pro, so the hardward has the potential to pull it off.
Playing 720p material in XBMC goes flawless.
I created debug logfiles. I made 2 runs.
First run started with 0 drops. After little than an hour I stopped playback and XBMC and made a copy of the logfile. By then over 1000 frames were droped, only a few in the first half hour but very frequently after that.
I quickly copied the log and started XBMC and the movie again with no reboot of the stick and very little time to cool down. The same pattern as the first run occurred (not immediatly or after a much shorter time, visibly it looked just like the first run!). I stopped when dropcount exceded 100, drops where now frequent again, by the time I hit stop it was already at 120 drops.
So this suggests it is indeed not a heat problem, a restart of XBMC again gives about 30 min of usable viewing time.
Logs:
Run 1:
http://xbmclogs.com/show.php?id=53316
Run 2:
http://xbmclogs.com/show.php?id=53320
As it is now, I can't watch a full 1080p movie using XBMC.