Sobel on EVMDM642

Hanief

Other Parts Discussed in Thread: CCSTUDIO

Hi,
I tried to use the Sobel function from the IMGLIB with my EVMDM642/camera/display. However, all I get is blank on the display. The relevant codes are as below (modified from example codes):
    while(1){
        /* copy data from capture buffer to array to display buffer */
        for(i = 0; i < numLines; i++) {
            DAT_copy(capFrameBuf->frame.iFrm.y1 + i * capLinePitch, Array1, disLinePitch);
            CACHE_wbInvAllL2(CACHE_WAIT);

IMG_sobel_c(Array1, Array2, cols, rows);

            DAT_copy(Array2, disFrameBuf->frame.rpFrm.buf + i * disLinePitch, disLinePitch);
            CACHE_wbInvAllL2(CACHE_WAIT);
        }
        ...
}
I also defined these locally somewhere up in the function:
#define cols 640
#define rows 480
and globally:
unsigned char Array1[640 * 480];
unsigned char Array2[640 * 480]={0}; /*intitialize coz Sobel produce 640 x 438 */

Anyone knows why this happens?
Thanks.
Hanief

over 16 years ago

0 Gagan Maur over 16 years ago

TI__Expert 8150 points

You may want to try:

   while(1){
        /* copy data from capture buffer to array to display buffer */
        for(i = 0; i < numLines; i++) {
            DAT_copy(capFrameBuf->frame.iFrm.y1 + i * capLinePitch, Array1, disLinePitch);
            CACHE_wbInvAllL2(CACHE_WAIT);

IMG_sobel_c(Array1, Array2, cols, rows);

            CACHE_wbInvAllL2(CACHE_WAIT); <-- MOVED ABOVE
            DAT_copy(Array2, disFrameBuf->frame.rpFrm.buf + i * disLinePitch, disLinePitch);
        }

If the above doesn't help, you may want to replace the sobel call with a memcpy to see if you get the same output as input. This will help understand if the issue is in the sobel call or not

0 Hanief over 16 years ago in reply to Gagan Maur

Intellectual 300 points

Hi Gagan Maur,
Moving the cache invalidate call doesn't seem to do anything. And the issue is in the Sobel call as expected. memcpy verifies that. I suspect it's something to do with the fact that the output image is 'cols' pixels wide and 'rows - 2' pixels tall.
Edited: I have also tried IMG_sobel instead of IMG_sobel_c. It produces 'striations' of vertical black lines on a white background (I'm imaging a black object on a white background). The shape of the object is quite visible to human eyes, but worthless for further processing.
Hanief

0 Gagan Maur over 16 years ago in reply to Hanief

TI__Expert 8150 points

You can include the C code in your build and single step to see what it is doing. You can get the source in the file: C:\CCStudio_v3.3\c6400\imglib\lib\img64x_c.src. Note it is a simple txt file. You can open it in any text editor and copy the sobel code.

Regards,

Gagan

0 Hanief over 16 years ago in reply to Gagan Maur

Intellectual 300 points

Firstly, the declarations below is incompatible with the FVID structure, so I discarded them & declared them as 'unsigned char' instead. Otherwise I'll get about 100 errors & warnings like 'expected an identifier', 'expected a ";"' even when there is one, 'declaration is incompatible with "VPORTDIS_Params EVMDM642_vDisParamsChan"', ' function call is not allowed in a constant expression'.
const unsigned char *restrict in,
unsigned char *restrict out,
After that, I managed to do as you suggested, build & load the program. Running it gives nothing (display is blank). When I try source-single step, the yellow arrow keeps going around in the for loop.

I found in a book that this "streaking" phenomena is caused by image noise. It recommended smoothing the image before applying filters like Sobel. But then, when I tried img_conv_3x3 & img_median_3x3, they both also have those streaking lines. Hanief

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Sobel on EVMDM642