Sharpening interlaced source

[feeras]

Hi,

Just a general question. Is there any benefits to the sharpening (or indeed other filters such as blurring) when the source is interlaced. The way i think about it, with all those combed-like lines whenever there is movement, sharpening it would be a waste of effort.

Any thoughts on this?

Cheers,
feeras

[racer-x]

First of all, the comb-like lines you refere to in interlaced videos won't show up when viewed on the TV, for witch it was created.

As far as filters, they are for effects. If you want to sharpen, blur, adjust color or whatever.

[snowmoon]

If you must use filters on interlaced materal, first split the materal into two streams ( top field and bottom field ) and filter each individually.

In AVISynth it would be similar to the following..

video = AVIsource(..)

video = SeparateFields(video)
even = SelectEven(video)
odd = SelectOdd(video)

# do filtering on each here

Interleave(even,odd).Weave()

[feeras]

Just a follow on question.

Would software like tmpgenc or others (procoder, mainconcept encoder, etc) take into account of the interlaced when they apply their (sharpening)filters? I would presume that they do.

Cheers,
feeras

[snowmoon]

Not unless they specifically mention it. There is usually a check box for interlaced source or field based, at least that's how TMPGenc works.

[SatStorm]

With virtualdub, most of the filters support interlace, so the "use fields as frames" technique isn't neccessary. Sometimes, this gonna help, but I don't believe that it helps with temporal filters that well...

Basicly, I can't find a good sharpening filter myself. Most of them are good for anime, but not for real video. If I need sharpening, then using the built in sharpen filter of Virtualdub, in a very low value (4 or 8 at best) gonna give you a bit this sharpen feeling we all want to see on our TVs.
Another alternative is Unsharp Mask filter. Personally, I don't like it (I tested this filter extensivly the last 4 months), but this is a matter of personal taste: Many likes a lot what this filter do to the picture, so maybe try it also your self, you might like it.

Of course, avisynth is a far more advance solution for filtering.

[DJRumpy]

I use AVISynth, and the built in filter:

Sharpen(value)

It does an acceptable job, although a value set too high (I usualy use 0.3 or less), will cause artifacts. If you need more, just string multiple Sharpen commands together:

Sharpen(.1)
Sharpen(.1)
Sharpen(.1)

This way, you can do a finer, more precise, sharpen than with a higher value. I definately agree with Snowmoon. When in doubt, seperate your fields, and work on each seperately.