1405 framegrabber with RS170 signal Acquisition WIndow?

[AndyN]

Hello,

What is the proper setting for the acquisition window with RS170 (standard monochrome 525 lines) with the 1405 framegrabber? The width and height are standard 640x480. I do not want to make it any smaller than it is.  I am referring to the MAX settings. Thanks.

[Matt_McLaughlin]

Hello AndyN,

Are you getting any sort of error with the current settings? With most cameras, you should be able to set the Acquisition Window to the following values:

Left - 0

Top - 0

Width - 640

Height - 480

Does that look to be working?

[AndyN]

My settings are Xoffset 113, Y offset 19. The image is not perfectly symmetric and very rarely not syncing perfectly.

When I tried both to be zero I lose 20 % of the image.

W 640 H480

[AndyN]

Here ia snapshot of the vid feed. Does it look to you like the interlacing is working properly? I am talking about the dark edges and "sawtoothing" in the right bottom corner. The picture "chair" is from a tv using a raw signal. I am cutting off the edges of the image, so the size is not the same.

[AndyN]

I found a generic rs170 camera file on NI ftp. Apparently the X offest should be 117. Still would like to know where it comes from etc.

[Matt_McLaughlin]

Hi AndyN,

I am not too familiar with the inner-workings of the RS170 standard, but I fill follow up and see if I can track down an answer on that.

For anyone who is interested, the Camera Support section of the NI FTP site will contain camera files for specific cameras and general camera standards, like RS170

[kellam]

Hi Andy,

The 117 comes from the offset in pixel clocks from the falling edge of the hsync to the first pixel of image data.  In an analog video signal (assuming you want square pixels), each line is 780 clocks long, of which 640 are image data, and the other 140 are blanking, syncs, and (if color) colorbursts.  Not all cameras follow the standard to the letter, so these parameters are modifiable to meet the foilbles of individual cameras.  If you'd like a more in-depth explanation, take a look at this document, which explains analog video signals in more depth.

-Jeff

[AndyN]

I read this document before and did not find those numbers mentioned explicitly.

Assuming that we have 640 cycles of pixel data, 117 for offset (going left in time scale), what is happening with the 23 others?

It is a good start,  but it would be nice if this document was rewritten once again with some respect for MAX settings and more numbers. It seems it is a compilation of documents form different sources.

[kellam]

The other pixels are the part of the front porch.  You'll see on the image of the video signal that the reference point is the falling edge of the sync signal.  The idle period shown on the diagram as being before the sync pulse is the front porch, and actually "belongs" to the previous line.

We have chosen not to document these settings more carefully because they are very confusing, and the exact values are not generally useful to customers.  The best way to choose the value for the acquisition windows offset is simply to point the camera at something bright, and adjust the window so that there isn't any black around the image.  Since the camera has a known image size (640x480 for RS-170), you can leave the window size set to that and just adjust the top and left edges.