Many of our customers ask what terms like "interlaced" and "progressive" mean, particularly in relation to HDTV (High Definition Television) and trying to determine the best format to choose for their intro video file.  There are many good resources on the Web that explain these concepts in much more detail but the following is provided to serve as a basic guide to what these terms mean.

Interlaced vs. Progressive

Choosing The Right Video Format For Your System

Supported Video Formats

Interlaced vs. Progressive

Most existing televisions available today display standard definition television (SDTV) signals which are interlaced.  Unless you have a newer extended definition television (EDTV) or an HDTV-capable model, you are probably watching interlaced images. 

The terms interlaced and progressive refer to how the TV displays the image on your screen.  Interlaced means that half the lines of the image are drawn first and then the second half are drawn.  They are interlaced because the first pass draws all the odd lines (1, 3, 5, ...) and the second pass draws all the even lines (2, 4, 6, ...), essentially weaving them together as you watch.  Naturally, this is done fast enough that your eyes cannot see the individual lines being drawn but the resulting image, particularly when compared with a similar progressive image, is relatively low quality.

Progressive systems draw each line of the entire image on each pass.  Two passes are still made but in each one all lines are drawn in sequence (1, 2, 3, ...).  This results in a much better looking image to the eye and eliminates jagged line effects that can be introduced by interlaced drawing.

Below are images representing interlaced and progressive displays.  The first two are the two individual passes, odd and even, of an interlaced display.  The third is the corresponding progressive image.

Interlaced:  Odd lines only

Interlaced:  Even lines only

Progressive:  All lines simultaneously

Choosing The Right Video Format For Your System

If you are planning to buy an intro video for your HTPC (Home Theater PC) system, there are two main factors to consider when selecting the right video format:  1) the display capabilities of the television and 2) the abilities of your HTPC to decode and display the file.

For your television, the best place to start is the owner's manual.  If you don't have the manual any longer, many manufacturers post their manuals in electronic form on their Web sites.  It should be able to tell you what formats you can support.  If the television is not digital or high-definition ready in some way, it will almost certainly only support 480i mode (see table of possible video formats below).

If your television is Extended Definition or High Definition-capable, there are several additional video formats it may support including 480p, 720p, 1080i, and 1080p.  Not all digital televisions support all of these formats so it is important to check your owner's manual to determine what your set is capable of displaying.

The second consideration is what format your PC can decode and display.  This is determined by the type and speed of the processor in your PC, the graphics card you have and, in most cases, how fast the hard disk drives in your system are. 

For 480i/p playback, we recommend a 1+ GHz processor and an AGP graphics card designed with video playback in mind. 

For 720p playback, a 2.5GHz+ processor and a 4X AGP graphics card are recommended. 

For 1080i playback, a 3GHz+ processor and a 4X AGP graphics card are recommended. 

For 1080p playback, a 3GHz+ processor and an 8X AGP graphics card are recommended. 

Note, all systems have different performance characteristics and there is no set rule for what will or won't work on your system.  We have provided sample videos in each supported format for you to download and test on your system before your purchase.  If the video plays correctly, without jumpy video or audio break-up, your system is capable of playing our video files.

Supported Video Formats