QUOTE(terry@android @ Jan 5 2012, 02:01 AM)
please mr angelictears. at least i know that. it seems like it will unable to recognize da device if u change it to sys with rw-r-r permission.
here da situation, i got 2 sd with one class 6 and class 4, i swap da class 4 to make sure it will play hd video but i wanna reserve internal only for app data and dalvik cache only as class 6 react faster. i wanna turn any app that i install into sys so app will conserve at system so da internal will be reserve, i m no gamer, but a maniac when it turn to anime, all app turn nice but only mx with it codec refuse me as a god. i try many way but fail, so i wanna some advise from u as a cooker for rom, how u intergrate alien app into sys?
and please...no childish advise please. i hav use android since 1.5, no brag as u re more superior as u choose to be dev.
anyway thanks for da advice.
i create my own setting to make my mi300 more superior than galaxy s coz i got no money to buy it. I learn and helped my friend on how to flash galaxy s, htc desire hd, galaxy ace and galaxy 5,galaxy tab, jailbreak iphone and ipad, but none of da owner thanks me for that. i been using mi300 almost 1 and a half year already.
but u re da only one dev who reply to all my selfish request, and i really appreciate it. i really thanks u for that. THANKS ALOT MAN
i dont really care bout ics, or miui coz what da point flashing to da new instead da old one is better?
Added on January 5, 2012, 2:21 amanyway keep up ur good work and thanks again for all ur work and support for this machine. glad i know u
Hmm, I am sorry that I forgot that you are a power user

I am apologizing for that.
The post before is the one that I usually do, but as I am not familiar with mx player, I am guessing that the apk structure it self doesn't allow manual run, and it must be install. This however usually solve by running the apk itself with proper permissions from the system/app/ folder. Which rendering the OS to think that the apk have to install in the system itself making it a sys app. Do note that the system/app folder does also need to set all permissions to -rwx, or at least -rw. I presume that you already know that.
And I believe that you have tried the above.
You can also try to make a flashable zip for that app, which usually the best way with 100% working, again note that I am not familiar with mx player and how the apk works, as most media player do need to install codec on other system and/or the sd card Android folder. By far in my experience no video player can be put as a sys app, different from music player as it uses native android codec and/or codec installed in sdcard/Android.
Other than that is to edit the ROM itself by putting the apk in the romzipfile/system/apps folder.
That's all that I can think of, other than that I presume that it is the apk's fault. But I am not certain, I will try to search and test it on my phone and see what I can find.