Question about Subtitle command

[HighInBC]

When I create a subtitle with avisynth, the subtitle is not interlaced. Meaning that the even and odd lines represent physical distance, not temporal distance.

Becuase of this, when I use the Subtitle command on an interlaced clip, the resulting subtitle shimmers when viewed on a TV.

Am I missing something fundemental? Or am I imagining the effect? If an image is not moving, like a subtitle, then the even and odd lines should be identical. I looked in the Subtitle documentation and saw nothing about interlacing.

Does anyone know how to take just the subtitle image and deinterlace it by duplicating fields?

I know I can do it with the ColorKeyMask command by putting the subtitles on a colored background, but I assume the anti-aliasing in the font will result in artifacts around the edges. Also, this would be very slow and an overly complicated solution.

Any help would be appreciated. Mabye there is a 3rd party plugin to do this?

Thanks,

HighInBC

[Wilbert]

Becuase of this, when I use the Subtitle command on an interlaced clip, the resulting subtitle shimmers when viewed on a TV.

Am I missing something fundemental? Or am I imagining the effect? If an image is not moving, like a subtitle, then the even and odd lines should be identical. I looked in the Subtitle documentation and saw nothing about interlacing.
I never thought about this. I don't understand why you would see a shimmering effect though.

I don't know how general it is, but i know that someone caps tv-shows where the subs are located in one field (thus not in the other field). Perhaps you can try that?

[IanB]

The text flickers because of the single pixel halo around the characters. This results in a high contrast difference between the contents of the fields at the top and bottom horizontal strokes of some characters.

A simple cheat to reduce the effect is to render the text half height then bilinear or soft bicubic upsize it to full height then mask it onto your image. This softens the vertical transitions and makes the halo 2 pixels high.

Also reducing the contrast between the text colour and halo colour can help a lot.

To improve performance when overlaying a static image use FreezeFrame(1, FrameCount()-1, 0) to force a cached access to frame 0 for all references.

IanB

[HighInBC]

"A simple cheat to reduce the effect is to render the text half height then bilinear or soft bicubic upsize it to full height then mask it onto your image. This softens the vertical transitions and makes the halo 2 pixels high."

hmm, that seems to me to be what would solve the interlacing problem. But when you make a subtitle on a blank background, change it then isolate it with say ColorKeyMask, then there are artifacts around the edges.

Considering the importance of the Subtitle command, I think that more options should be added to it(either in the core or via 3rd party plugin).

There needs to be an option to blur the mask for the subtitle to avoid the sharp contrast(I find subtitles on a black screen that have been blurred a little look better at the edges).

And another option to make sure the even and odd feilds are identical in a subtitle(for interlaced video).

Perhaps someone knows of a 3rd party plugin for subtitle that can do this? I am working on a feature for TV and it has to look professional. I am attempting to demonstrate to a local video club how avisynth can go from raw footage to final render in one file.