drcl
13th May 2005, 15:27
Why would i want that?
Well acording to what i have read, DCT based video compression doesnt like hard edges like where there are small black strips along the edges of the picture.
So the obvious thing to do is letterbox to a 16 pixel border using letterbox(16,16,16,16) or similar....
thats fine on a 720x576 but on smaller pictures a 16 pixel border impinges on the tv screen and also on interlaced where it should be 32 pixels to cover the vertical chroma.
so i figure instead of using letterbox(8,8,8,8) on vcd and letterbox(32,32,16,16) on dvd it would be better just to apply a letterboxing to the luma. This would leave the original bad edge in the chroma in place of a very hard edge if I was trying to avoid the letterboxing being viewable.
not sure if I am explaining it adequately or if my theory is correct but if someone knows of a filter that only letterboxes the luma I would be very grateful.
While writing this I just realised I could do this with Mergeluma/mergechroma but I would prefer a filter if ther is one because it would probably be optomised.
Well acording to what i have read, DCT based video compression doesnt like hard edges like where there are small black strips along the edges of the picture.
So the obvious thing to do is letterbox to a 16 pixel border using letterbox(16,16,16,16) or similar....
thats fine on a 720x576 but on smaller pictures a 16 pixel border impinges on the tv screen and also on interlaced where it should be 32 pixels to cover the vertical chroma.
so i figure instead of using letterbox(8,8,8,8) on vcd and letterbox(32,32,16,16) on dvd it would be better just to apply a letterboxing to the luma. This would leave the original bad edge in the chroma in place of a very hard edge if I was trying to avoid the letterboxing being viewable.
not sure if I am explaining it adequately or if my theory is correct but if someone knows of a filter that only letterboxes the luma I would be very grateful.
While writing this I just realised I could do this with Mergeluma/mergechroma but I would prefer a filter if ther is one because it would probably be optomised.