[Motmot] motmot.cam_iface + isight + snowleopard

[Laurent Perrinet]

Hi list!

I'm trying to grab frames from the iSight of a macbook. This was working well with pysight (*) but broke with the advent of Snow Leopard.

I was trying the motmot.cam_iface library since it appears to be implementing all I need. It seems to work in Leopard, but I thought I should share my adventures in trying to make it work on my platform (snow leopard) which drops support for Carbon and tries to push 64-bit forward.

First I tried the compiled version on:

http://code.astraw.com/libcamiface/download/libcamiface-0.5.9-Darwin.dmg

the /usr/bin/liveview-glut-quicktime and /usr/bin/liveview-glut-mega work just fine. they apparently run in 32-bit mode:

$ file /usr/bin/liveview-glut-mega
/usr/bin/liveview-glut-mega: Mach-O executable i386  

now, I try to use the python interface. obviously, using macports or apple's 64-bit version says:

$ /opt/local/bin/python
Python 2.6.4 (r264:75706, Oct 31 2009, 11:56:27) 
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 
>>> import sys
>>> sys.maxint
9223372036854775807
>>> import motmot.cam_iface
>>> # Also the example in ../README.rst -- so keep in sync
... import pkg_resources
>>> import motmot.cam_iface.cam_iface_ctypes as cam_iface
import numpy as np

mode_num = 0
device_num = 0
num_buffers = 32

Could not open shared library for backend "libcam_iface_mega.dylib"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/motmot.cam_iface-0.5.0-py2.6.egg/motmot/cam_iface/cam_iface_ctypes.py", line 55, in <module>
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/ctypes/__init__.py", line 353, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: dlopen(libcam_iface_mega.dylib, 6): no suitable image found.  Did find:
	/usr/lib/libcam_iface_mega.dylib: mach-o, but wrong architecture


So I tried to compile myself (that is in 64-bit mode) using the latest code in http://github.com/motmot/libcamiface
::

sudo port install glew
mkdir build
cd build
cmake .. -DCMAKE_GENERATOR=Xcode
make
cpack



However I could not compile whatever combinaison I tried (except pretending I was on Leopard 32-bit in xCode... certainly a problem with carbon which is dicontinued in SL). I was clueless whether I would see any other alternative than switching back to Leopard?

So I gave a try to the python distributed by enthought : 'Enthought Python Distribution Academic Download' : http://www.enthought.com/products/edudownload.php , that is 'only' 32-bit... sounded like an asset to me...

it comes with all batteries inluded (numpy, scipy, matplotlib) + some bonus (mayavi, ...), but in particular easy_install:

sudo easy_install motmot.cam_iface

then in ipython:

import pkg_resources
import motmot.cam_iface.cam_iface_ctypes as cam_iface
import numpy as np

mode_num = 0
device_num = 0
num_buffers = 32

cam = cam_iface.Camera(device_num,num_buffers,mode_num)
cam.start_camera()
frame = np.asarray(cam.grab_next_frame_blocking())
print 'grabbed frame with shape %s'%(frame.shape,)


just ... works!

so the moral is: early optimization (= 64-bit) is evil!

you may see a dummy demo: http://www.incm.cnrs-mrs.fr/LaurentPerrinet/SimpleCellDemo 

cheers,
Laurent

* http://livingcode.blogspot.com/2005/10/pysight-preview.html
----
Laurent Perrinet - INCM (UMR6193)/CNRS 
http://incm.cnrs-mrs.fr/LaurentPerrinet