Thin Lines Vibrating, Why? at DVinfo.net

Ben Gurvich · May 10th, 2005, 09:05 PM

I have some footage with some striahgt lines in it creating a strobing effect, which does not look good.

Any ideas why this is happening and how to reduce it?

My guess is its something todo with interlacing?

Cheers,
Ben Gurvich

Jimmy McKenzie · May 10th, 2005, 09:15 PM

That's exactly correct. Your raw footage will be difficult to correct to remove this malaise. A very slight Gaussian blur or scaling the clip down a bit or even a pip will eliminate this, but the artistic vision of the scene could be compromised. If the scene is short enough you could de-interlace. Or try the flicker removal option in your NLE. This is easy to get at in Premiere.

If the area strobing is text, use a sans serif font or avoid "font with feet". Arial black , Tahoma and Helvetica are good choices.

If the area is a raster graphic, be sure to use lines of no less than 4 point size. You can also feather larger edges to keep flicker to a minimum.

The above assumes the trouble is during the edit stage. If this persists once you have exported to dvd, perhaps try a different encoder/dvd authoring program. They do come in various shapes and sizes and the quality is variable.

Boyd Ostroff · May 10th, 2005, 09:58 PM

The reason for the flicker is that a thin line can exist (for example) in the odd 60i field but not the even field. Therefore every 1/30 second it flickers on and off.

Glenn Chan · May 10th, 2005, 10:34 PM

Which editing program are you using?

In most programs, there is a de-interlace setting/option that can blend or interpolate fields to get rid of the interlace flicker. Blend fields is usually good.
Flicker removal filters are also good.

In Vegas, you can try unsharp mask with negative values (-0.500 amount, 0.005 radius, threshold bout 0.040 or so).

May 10th, 2005, 09:05 PM	#1
Ben Gurvich Major Player Join Date: Dec 2003 Location: Australia Posts: 329	Thin Lines Vibrating, Why? I have some footage with some striahgt lines in it creating a strobing effect, which does not look good. Any ideas why this is happening and how to reduce it? My guess is its something todo with interlacing? Cheers, Ben Gurvich

May 10th, 2005, 09:15 PM	#2
Jimmy McKenzie Major Player Join Date: Jan 2004 Location: Waterloo Ontario Posts: 721	That's exactly correct. Your raw footage will be difficult to correct to remove this malaise. A very slight Gaussian blur or scaling the clip down a bit or even a pip will eliminate this, but the artistic vision of the scene could be compromised. If the scene is short enough you could de-interlace. Or try the flicker removal option in your NLE. This is easy to get at in Premiere. If the area strobing is text, use a sans serif font or avoid "font with feet". Arial black , Tahoma and Helvetica are good choices. If the area is a raster graphic, be sure to use lines of no less than 4 point size. You can also feather larger edges to keep flicker to a minimum. The above assumes the trouble is during the edit stage. If this persists once you have exported to dvd, perhaps try a different encoder/dvd authoring program. They do come in various shapes and sizes and the quality is variable.

May 10th, 2005, 09:58 PM	#3
Boyd Ostroff Wrangler Join Date: Dec 2002 Location: Mays Landing, NJ Posts: 11,802	The reason for the flicker is that a thin line can exist (for example) in the odd 60i field but not the even field. Therefore every 1/30 second it flickers on and off.

May 10th, 2005, 10:34 PM	#4
Glenn Chan Inner Circle Join Date: Jun 2003 Location: Toronto, Canada Posts: 4,750	Which editing program are you using? In most programs, there is a de-interlace setting/option that can blend or interpolate fields to get rid of the interlace flicker. Blend fields is usually good. Flicker removal filters are also good. In Vegas, you can try unsharp mask with negative values (-0.500 amount, 0.005 radius, threshold bout 0.040 or so).