Can't make fakenect working with python wrappers

[rguillome]

Hi,

Here is the output I get while trying to launch the python demo_cv_aysnc.py with fakenect. I specified the LD_PRELOAD and FAKENECT_PATH env var :

Traceback (most recent call last):
  File "demo_cv_async.py", line 2, in <module>
    import freenect
ImportError: /usr/local/lib/libfreenect_sync.so.0.5: undefined symbol: freenect_camera_to_world

I investigated a little bit since this wiki page presents a sample with this python demo, it should be my mistake ...

So I dig into the freenect import build from C libs with cython : the libfreenect_sync.h (and so on libfreenect_sync.c) declares a freenect_sync_camera_to_world and its implementation makes a call to freenect_camera_to_world. But fakenect.c which should fake the call to the real kinect I/O doesn't implements this method but moreover, the libfreenect.h doesn't declares this signature...

Why this method isn't overrided or just cloned under the fakenect.c source code?
I will try a fork but It should be nice to have your return BTW.

Regards,
Guillaume

[piedar]

The method freenect_sync_camera_to_world() is declared in freenect_registration.h, but your observation is correct: it has not yet been implemented in fakenect. A patch is always welcome!

[rguillome]

I dig deeper and found that my first analysis was Wrong. Indeed, a patch has already been made adding the header lib_registration.h to the c_sync wrappers which is the synchronous bridge between python wrappers and the libfreenect (which by design is asynchronous).
With the LD_PRELOAD env var, the fakenect resulting libs only overrides a couple of target functions that make real call to the device. So freenect_camera_to_world should be offered by the usual libfreenect.so.

I finally expected a mistake in the libraries linking configuration.

Two tests that shows that having the same library name between the fakenect one and the usual one is (now?), a mistake :

± |debian U:2 ?:1 ✗| → export LD_PRELOAD=

± |debian U:2 ?:1 ✗| → ldd freenect.so 
	linux-vdso.so.1 (0x00007ffda99b8000)
	libusb-1.0.so.0 => /lib/x86_64-linux-gnu/libusb-1.0.so.0 (0x00007f49e531f000)
	libfreenect.so.0.5 => /usr/local/lib/libfreenect.so.0.5 (0x00007f49e5110000)
	libfreenect_sync.so.0.5 => /usr/local/lib/libfreenect_sync.so.0.5 (0x00007f49e4f0c000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f49e4cef000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f49e4950000)
	libudev.so.1 => /lib/x86_64-linux-gnu/libudev.so.1 (0x00007f49e492d000)
	/lib64/ld-linux-x86-64.so.2 (0x000055ea25885000)
	librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f49e4725000)

But of course, without the LD_PRELOAD, it expects the connected device...
So with the documented LD_PRELOAD :

± |debian U:2 ?:1 ✗| → export LD_PRELOAD="$LIBFREENECT_SRC_PATH/libfreenect/build/lib/fakenect/libfreenect.so"

± |debian U:2 ?:1 ✗| → ldd freenect.so 
	linux-vdso.so.1 (0x00007fff5edbd000)
	LIBFREENECT_SRC_PATH/libfreenect/build/lib/fakenect/libfreenect.so (0x00007f5019c80000)
	libusb-1.0.so.0 => /lib/x86_64-linux-gnu/libusb-1.0.so.0 (0x00007f5019a37000)
	libfreenect_sync.so.0.5 => /usr/local/lib/libfreenect_sync.so.0.5 (0x00007f5019833000)
	libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f5019616000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f5019277000)
	libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f5018f71000)
	libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f5018d6d000)
	libudev.so.1 => /lib/x86_64-linux-gnu/libudev.so.1 (0x00007f5018d4c000)
	/lib64/ld-linux-x86-64.so.2 (0x00005606cedcd000)
	librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f5018b44000)

As shown, the libfreenect.so.0.5 => /usr/local/lib/libfreenect.so.0.5 (0x00007f49e5110000) line disappear, probably by the fakenect lib overriding...

Altering the generated fakenect lib from libfreenect.so to libfreenect_fake.so does the job.
The change in the file fakenect/CMakeLists.txt (change the OUTPUT_NAME):

set_target_properties ( fakenect PROPERTIES
  VERSION ${PROJECT_VER}
  SOVERSION ${PROJECT_APIVER}
  OUTPUT_NAME freenect_fake)

and us the libfreenect_fake.so as the preloaded library with LD_PRELOAD.

I will create a patch tomorrow

[rguillome]

This issue is corrected by the Pull request : #511