Why are my video grabs not 4x3?

[avpeterjohn]

I'm using PAL 4X3 & I have noticed that the background images included in DVDWS are 768x576, which is 4x3 in proportion, whereas the grabs I make from the video to use as menu backgrounds are 720x576. Why is this ?
Using my grabs produces vertical black bands at the edge of the menu screen.

[Devil]

The PAL format is actually much larger than 768x576. I forget the H size but the V is 625. Only the 768x576 is permissible for video info, the rest being for synchronisation pulses, black level, blanking, setting gain etc. However, TVs are designed to display only about 680x520, give or take a few grams, because the position of the display cannot be guaranteed as the moment that a synch pulse triggers the time base depends on the signal strength, the trigger sensitivity etc. The difference between the displayed pic and the theoretical one is called overscan. PAL definition says that the image must be multiple of 16 wide so, for economy of bandwidth, it is perfectly permissible to use only 720 (e.g., DV) or 704 (e.g, some analogue MJPEG capture systems), leaving the remaining 48 or 64 pixels black. As these fall into the overscan area, these are not seen, so do not matter. But, whichever format is used, the image is always 768 pixels wide. The DVD spec accepts 704, 720 and 768 pixels of actual image. This is also why WS2 shows a title area much smaller than the image, to make sure that the titles, buttons, sub-titles are all fully visible and never cut off by your TVs overscan.

I've two Panasonic prosumer DV cams and the black border on one is symmetrical and on the other is somewhat offset. This is called manufacturing tolerances.

Whatever, the aspect ratio of the frame is always 768x576 for PAL, even with 16:9, which is anamorphic or letterboxed, depending on the system.

[avpeterjohn]

Thanks Devil.
I think I understand it !?! Pal DV is 720 X 576. Yes ?