Hi friends,
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:
------------------------------CODE-----------------------------------------
#define cdSTDCALL __stdcall
typedef void cdSTDCALL cdSOpen(cdContext contextH, cdPermission,
cdError* err);
typedef void cdSTDCALL cdSClose(cdContext contextH, cdError* err);
typedef void cdSTDCALL cdSRead(cdContext contextH, void* buf,
cdUInt32* bufsize, cdError* err);
typedef void cdSTDCALL cdSWrite(cdContext contextH, const void *buf,
cdUInt32* bufsize, cdError *err);
typedef void cdSTDCALL cdSSeek(cdContext contextH, cdWhence, cdInt32
offset, cdError* err);
typedef cdInt32 cdSTDCALL cdSTell(cdContext contextH, cdError* err);
typedef void cdSTDCALL cdSProgress(cdContext contextH, cdUInt16
percentDone, cdError* err);
/* cdStream
*/
typedef struct {
cdContext contextH;
/* stream I/O function pointers */
cdSOpen* open;
cdSClose* close;
cdSRead* read;
cdSWrite* write;
cdSSeek* seek;
cdSTell* tell;
} cdStream;
/* cdStgMedium
*/
typedef struct {
cdMemType Type; /* Type of the medium (u). */
union {
cdChar* lpszFileName;
cdStream* pStream;
#ifdef macintosh
cdFSSpec* pFSSpec;
#endif
}u; /* Union of all transfer medium */
} cdStgMedium;
------------------------------\CODE----------------------------------------
and this is the function definition that should give me access to the
data stream (available via DLL):
------------------------------CODE-----------------------------------------
cdCAPI CDGetReleasedData(
cdHSource hSource,
cdProgressCallbackFunction * pCallbackFunc,
cdContext Context,
cdProgressOption ProgressOption,
cdReleaseImageInfo* pInfo,
cdStgMedium* pStgMedium
);
------------------------------\CODE----------------------------------------
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:
------------------------------CODE-----------------------------------------
# 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)]
class memunion(Union):
_fields_ = [("lpszFileName", c_char),
("pStream", 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))
------------------------------\CODE----------------------------------------
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?
Best regards and thanks,
Matt
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