Actually, you can tell the difference if the 1080i source is: a) Truly interlaced (each field is temporally unique) b) Full of horizontal motion
So, you can see the difference in a sports broadcast with text scrolling left to right on the bottom. Each field is really only 540 lines. This field is scaled up to 1080 lines (if you have a 1080p panel, otherwise, its probably 768 lines). The problem that shows up with scaling each field up to full screen is that the flat tops of the letters seem to bob up and down due to the 1/2 line offset between the field pairs. So you will see horizontal lines sort of shake at the tops.
A more sophisticate deinterlacing algorythm will combine several fields to a single frame. This eliminates the shimmer on horizontal lines, but usually gets it a little wrong for text scrolling sideways. Side-scrolling text is extremely hard to deinterlace. The main issue is that motion vectors can get confused with side-scrolling text. So errors will show up with the edges of the text in this case.
1080p content skips all of this issue by having no fields, just full size frames. Some 1080i content is really 1080p content that sends half the lines at a time. In other words, the fields are not temporally unique. This sort of content is extremely easy to deinterlace to a 1/2 frame rate 1080p.
Hope this helps. I'm actively solving some of these problems in the industry.
Reader Comments (Page 1 of 1)
HarperBrad @ Jul 24th 2006 2:33PM
Actually, you can tell the difference if the 1080i source is:
a) Truly interlaced (each field is temporally unique)
b) Full of horizontal motion
So, you can see the difference in a sports broadcast with text scrolling left to right on the bottom. Each field is really only 540 lines. This field is scaled up to 1080 lines (if you have a 1080p panel, otherwise, its probably 768 lines). The problem that shows up with scaling each field up to full screen is that the flat tops of the letters seem to bob up and down due to the 1/2 line offset between the field pairs. So you will see horizontal lines sort of shake at the tops.
A more sophisticate deinterlacing algorythm will combine several fields to a single frame. This eliminates the shimmer on horizontal lines, but usually gets it a little wrong for text scrolling sideways. Side-scrolling text is extremely hard to deinterlace. The main issue is that motion vectors can get confused with side-scrolling text. So errors will show up with the edges of the text in this case.
1080p content skips all of this issue by having no fields, just full size frames. Some 1080i content is really 1080p content that sends half the lines at a time. In other words, the fields are not temporally unique. This sort of content is extremely easy to deinterlace to a 1/2 frame rate 1080p.
Hope this helps. I'm actively solving some of these problems in the industry.