Michael Zucchi

 B.E. (Comp. Sys. Eng.)

  also known as zed
  & handle of notzed


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Monday, 25 March 2013, 12:03

#$#@$ Android

One of those "I can feel the hair going grey and falling out" mornings. Although at least it wasn't one of those "I made every mistake I could have, every time I did anything" one. My throat is hoarse from all the screaming of definitely un-pc obscenities.

I'm trying to get some jjmpeg stuff working on android - but I can't use the jjmpeg android branch due to licensing issues. I need to use a fully shared library version.

Compiling the code was easy enough but trying to use shared libraries on Android turned out to be a complete head-fuck.

First, for some fucked reason although shared libraries are placed into a per-architecture location, the bloody library path isn't setup to automatically use it. So you have to hard-code all the architecture into the dlopen() calls.

Actually second, it's even worse than that, you need to use absolute paths for dlopen() otherwise it doesn't work. I just hard-coded it, a stack overflow answer stated that finding the path from Java was 'trivial', but then neglected to include which api trivially provided it. I didn't really want to change jjmpeg anyway.

And thirdly, it's flaccid linker doesn't support versioning of the shared libraries. To fix that I hacked up ffmpeg/library.mak to only create non-versioned sonames, and then hacked a build script to make it compile properly as with that change it didn't seem to want to build the libraries properly. I did this by specifying each lib*/*.so manually as the build target.

And the fun's only just started, i've still got a pile of C and NEON code I've got to get to work ...

Update: Oh fucking joy, no complex numbers now.

Update 2: Well I managed to replace complex.h with a few lines of #defines - fortunately they're complex numbers are in the compiler, just not in libm, and apart from the basic arithmetic I only needed creal/cimag and conjf.

And somehow, after re-arranging 1500 lines of C and 1500 lines of NEON assembly language, creating JNI wrappers, and hooking it into ffts and jjmpeg/head ... it worked almost first time. I'd set myself all week to get that far so i'm pretty chuffed, even if the headache from the days earlier tribulations hasn't yet receded.

I really have the beagleboard and a GNU operating system to thank for that - without being able to develop on a proper system first it would've been a nightmare.

Time for a couple of glasses of nice Barossa red methinks.

Tagged android, hacking, jjmpeg, rants.
Another pointless bruhaha at an IT conference | clAmdFft
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