question about real VCD quality

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I am doing my first experiences creating vcds. For now I am converting most of my anime collection, saving an awful lot of space. But I notice that the edges get weird. A diagonal line for example do not get straight, it looks more like a stairway or a sequence of dots. I beleive this is due to the resolution cause video vertical resolution is usually 480 pixels and vcd is exactaly half of it. My question is: this is normal of is there any way I can avoid it? Does interpolation have anything to do with this? I use vitual dub and tmpgenc, burn with nero 5 with a pentium 700 and 256M ram. Run vcds in a Pioneer dvl 909.

Thanks!

-- Ricky Nobre (rickynobre@rionet.com.br), January 30, 2001

Answers

What you observe is a limitation of VCD; it uses just one of the fields (240 or 288 lines) and on playback repeats it to make one frame. The other original field, which could have made the diagonal line appear smoother, isn't used at all by the encoding to MPEG-1. Some will argue that you can give the whole interlaced original 480 lines to the encoder and it will interpolate the two fields to create a unique 240-line new pix to use, compared with just giving it only 240 to begin with; fine, but during playback of the VCD you still have just that one 240-line field that will be repeated twice to make a frame and your staircase-looking diagonal line is still as staircase-looking as ever. This is one area where VHS still looks better because the 480-line interlaced structure is fully used; if it really bothers you I suggest going up to SVCD, where all of the 480 lines are used.

-- Mehmet Tekdemir (turk690@yahoo.com), January 31, 2001.

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