Using CVI to Read an AVI

[shawnhunt]

Hi,

I am trying to read an AVI in my CVI code, but it isn't working.  I am able to read the same AVI fine in a VI, just not on the C side of things.  Here is the code I am using:

	AVISession session = 0;
	session = imaqOpenAVI("C://MKX.avi");
	int error = imaqGetLastError();

	AVIInfo *info = NULL;
	imaqGetAVIInfo(session, info);

	printf("There are %d frames at %dx%d\n", info->numFrames, info->height, info->width);

The call to imaqGetAVIInfo returns null.  I made sure the path to the AVI was correct. 

Any suggestions are much appreciated.

Shawn

[ChristopheC]

Have you tried "C:\\MKX.avi" for the path? (use backslashes instead).

-Christophe

[shawnhunt]

Whoops, that was an error in my code posting.  That was left over from trying "/" instead of "\\". 

imaqOpenAVI returns 1, which I think means it opened it okay.  I also did a imaqGetLastError after the imaqOpenAVI and it returns 0.  I also added an error check after imaqGetAVIInfo and it comes back with: -1074395269 Null pointer.

Am I just missing something obvious with my code?

Thank you for the reply.

[BlueCheese · Accepted solution]

---

@shawnhunt wrote:

Whoops, that was an error in my code posting.  That was left over from trying "/" instead of "\\". 

imaqOpenAVI returns 1, which I think means it opened it okay.  I also did a imaqGetLastError after the imaqOpenAVI and it returns 0.  I also added an error check after imaqGetAVIInfo and it comes back with: -1074395269 Null pointer.

Am I just missing something obvious with my code?

Thank you for the reply.

---

I haven't looked up the documentation for that function, but it looks like from the way you called the function (and also the error code) that you are passing it a NULL pointer. The function would have no way to return the info you asked for with the way you are calling it. I imagine it expected you to allocate the structure and pass it by reference.

Your code should probably be modified like this:

AVIInfo info;
imaqGetAVIInfo(session, &info);

Hope this helps,

Eric

[shawnhunt]

Ah, yes, totally my fault.  I was having a total brain freeze on that one.  Thank you!