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Originally Posted by bkman
Well, yes I understand that, but it doesn't really answer my question about how to deal with DVD's that require cropping off the black bars.
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When you crop away the black mattes from a DVD source, the important thing is too make sure you end up with horizontal and vertical resolutions that are in multiples of 16 pixels (aka: "mod16").
However, because this is not always possible with cropping alone, you may end up having to re-size the image slightly until you obtain a "mod16" frame size.
In theory, it is possible to display an encode at any shape you want, once the required AR signalling value has been applied.
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Originally Posted by bkman
Another related question is: Why are the padding bars even there on the DVD? Are they part of the original image as it was meant to be displayed or just artifacts of DVD conversion?
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The black mattes are there because that is what was agreed upon and later defined within the MPEG-2 DVD standard.
It was decided that the most effective way of displaying images with different aspect ratios was to overlay the "image portion" onto a "black background portion" (aka: matte) with a fixed Frame Aspect Ratio (FAR). So this is why all commercial PAL DVD's have an fixed FAR of 720x576 or 5/4. All commercial NTSC DVD's have a fixed FAR of 720x480 or 3/2.
Hope that helps.... a bit
