Matt <[EMAIL PROTECTED]> wrote:
> Okay so well, I have quite a problem right now with a file stream. What
> I am doing is to use the Cannon SDK dlls to get control over my old
> Cannon A60 Camera for some surveillance useage.
>
> By using ctypes it all worked well until now. I am able to load the
> dlls, use a lot of functions, am able to connect to the camera, read out
> some params, send commands etc... but now I am stuck with reading the
> picture data.
>
> In C the code looks as follows (found in an supplemental *.h SDK file:
[snip]
> So, since I'm no C-Professional, I can only guess what that code does.
> With some previous commands I tell the camera to make a picture. This
> picture is then automatically moved to the PCs RAM and with the function
> above (CDGetReleasedData) I should be able to access this stream. Now I
> havn't accessed any stream with ctypes yet so I have only a rough idea
> how it could work.
>
> The following are the relevant parts of my code that don't work:
>
>
> # Definitions:
>
> class cdReleaseImageInfo(Structure):
> _fields_ = [("SequenceID", c_uint),
> ("DataType", c_uint),
> ("Format", c_ubyte),
> ("DataSize", c_uint),
> ("Filename", c_char * 2)]
>
>
> class cdStream(Structure):
> _fields_ = [("contextH", c_uint),
> ("open", c_uint),
> ("close", c_uint),
> ("read", c_uint),
> ("write", c_uint),
> ("seek", c_uint),
> ("tell", c_uint)]
These c_uints would be better as c_void_p at minimum
Howerver I suspect you are going to have to implement these callback
functions - read this section of the manual
http://docs.python.org/lib/ctypes-callback-functions.html
I suspect it will call back your functions for the given
functionality, eg "open", "close" etc...
> class memunion(Union):
> _fields_ = [("lpszFileName", c_char),
This should be c_char_p I suspect...
> ("pStream", cdStream)]
and this should be POINTER(cdStream)
> class cdStgMedium(Structure):
> _fields_ = [("Type", c_uint),
> ("u", memunion)]
>
>
>
>
> # command:
>
> datainfo = cdReleaseImageInfo()
> data = cdStgMedium()
> errorcode = cdsdk.CDGetReleasedData(devicehandle, byref(cbfunct),
> c_uint(1), c_uint(1), byref(datainfo), byref(data))
>
> The function "cdsdk.CDGetReleasedData" itself gets executed correctly,
> but returns an "Invalid Parameter" errorcode. there's also no useful
> data whereas datainfo gets written correctly. I know that my cdStream
> can't work, facing the C-code, but what'd be the right cdStream class?
> What can I do? Any ideas?
I've noted some obvious problems above.
To get this to work will require some C knowledge. If they supply
some example C code I'd work through that translating it line by line
to python+ctypes.
--
Nick Craig-Wood <[EMAIL PROTECTED]> -- http://www.craig-wood.com/nick
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