Getting Rid Of Unwanted Lines
Another great technique to apply to your video clips as you are encoding them is to use deinterlacing. If your processing systems allows, this feature will let you select from odd lines, even lines, blend, adaptive, and possibly even a few more options. Normal video that gets recorded by a camera or broadcast into your television is made up of alternating lines, or what we call interlacing. We use the reference that video runs at 30 frames-per-second here in America. This means video captures or reproduces 30 individual frames every given second. That's what creates the illusion that movement over time. If you could slow down the process fast enough for the human eye to see, you would actually see that there are 60 fields-per-second. It takes two fields to make up one single frame. A field is made up of half of the lines of resolution of the full-framed image. The video signal is actually writing, or drawing onscreen if you will, every other line starting from the top of the screen down. Then, in one-sixtieth of a second, it goes back and fills in the missing lines. This happens so fast that the human eye cannot see this happening. Where this interlacing effect is noticeable to the human eye is when you have small, thin horizontal lines (especially one or two pixels high). These lines may be stationary, yet your eyes may perceive that they appear to be flickering. This is because of the interlacing effect, or redrawing of alternating video scan lines. When you compress your video, the nature of compression is to remove small details of unwanted data. Sometimes, these details get lost with compression, yet we don't want to have them removed. Using the deinterlacing effect, you can avoid flickers and possibly keep wanted details within an image as it is being compressed. Just about any system that allows you to deinterlace an image will give you at least the choice whether to select odd (the first set of lines drawn) or even (the secondary lines drawn). Blending is a feature that mixes the pixel information from two lines and creates one new line with the "blended" information. Sometimes, this is the only choice, but be aware that blending tends to soften your image because you are combining pixel information.