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Originally Posted by RichDanby
So I guess it only shows the modes for the format your using. I'm even more confused on the number of lines in PAL now, most sources say 625 but some use 576. I'm fairly sure some lines are used for teletext so that might be the difference.
The reason for all this is to avoid any scaling of the image. If the incoming signal is 576 lines, and the display is expecting 576 lines, then you really want to record and output 576 lines.
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Now this is something I know a bit about. It's my job to know
There is a difference between tha analog signal comming through and what results in a picture. The full PAL image size is considered to be 768x576 if digitized i nto a computer. D1 video (DV cameras things) will digitize at 720x576. Nothing is lost, the line of video is just representet by a slightly smaller number of pixles. When doing Special effects and thing there are lots of things to think about because of this but lets drop it for now.
625 is the full number on TV scallines for PAL. Like you wrote, the "leftover" ones are there for teletext and other things. If you have anolder TV set that is out of sync you can see flickering white dots at the top (and/or bottom) outside the picture area. That is why they are not digitized by Video/TV cards. If we did we could look at the teletext of recorded shows, which would actually be pretty cool cme to think of it.
NTSC also has more lines that 480. Can't remember exactly byt prabably around 525 lines.