Home Theater PC and DVD-Video Processing

DVD Video has revolutionized the consumer entertainment industry like no other format before it, and the ever decreasing entry price has the world replacing their outdated equipment at an unprecedented pace.  Prices have spurred purchase of Hollywood content as never before, and the thriving sales and rental market of DVD will soon ensure the demise of tape as a medium.  Below is a primer on what's available for DVD playback on a PC and why it maybe a better solution for you. 

History of DVD-Video and Progressive Scan

Our entertainment has been defined by the NTSC format standardized 50 years ago by the national broadcasters for delivery of television.  To display anything on the NTSC TV, the video signal must be fed in the interlaced format.  The introduction of PC based DVD proved that with compatible displays, progressive delivery offers higher quality image of video, and the industry is catching up to comply with the standards in the new equipment that is being introduced.  

Progressive Scan DVD requires high-frequency display, such as today's direct view and rear projection HD-Ready TV, Computer Monitor, Plasma Flat TV, or Front Projector.  The signal cannot be displayed on older analog interlaced sets. 

To understand Progressive Scanning for DVD material, you must first understand how the image is laid on the DVD disk.  DVD standard states that the video image is encoded in 720 lines horizontally and 480 lines vertically.  This image is defined as a "frame", a full snap of a picture from the original film with the full 720x480 lines of image. 

This image will be divided to two halves by taking each alternate lines to create a "field".  The division of the picture is required to display on an analog NTSC set which can show only half the picture in each pass of the electron gun, hence the term "interlaced".  In the next pass, it will draw the alternate line and repeat the scan 60 times per second.  The process reveals dark lines inbetween each line of the picture called scan lines.  The eye can be fooled on smaller TV sets, but the same image blown up to twice, three times, or four times it's original size becomes torturous as is the case with large screen displays. 

Progressive scan imaging was designed to show both of the fields in one pass, doubling the scan frequency and eliminating the artifact of interlacing.  To do so required re-engineering the display device and the type of input connector used. To define the interlaced process, a video signal is described as 480i, whereas progressive signals are identified as 480p. 

In the early days of DVD video, manufacturers and the committee setting the DVD standard known as the DVD Consortium bickered heavily over making progressively scanning players available to the public.   Rumours circulated in the industry about brand new players that were destroyed due to pressures from the Hollywood studios and the Motion Pictures Association of America as they combatted the ability of the home user to obtain high-resolution video quality and the lobbying groups high-hopes on the DIVX video delivery standard to combat piracy of their property.  The Home Theater PC because the vehicle for the first introduction of true progressive scan DVD decoder.

What is Progressive scan DVD

In this instance, an explanation into how information is stored on the DVD disk is pertinent to the topic. There are currently two distinct types of video technologies available on the digital video MPEG-2 formats.

Video - Derived from video sources which are captured as interlaced images at 30 frames per second.  This is the source often used for television studio cameras and hand held camcorders. 

Film - Derived from 24 frames per second sources, which must be converted to 30 frames per second, using a technique called 3:2 pulldown, or converting the  24 fps. material into 30 fps.

MPEG-2 Decoding Methods

The PC utilizes two methods to decode MPEG-2 video, BOB and WEAVE.  When presented with sources from video cameras (interlaced video), the BOB method is often employed, while WEAVE is normally used for film sources.

All PC DVD software decoders do quite well with film based sources, but do not perform as well on video based material.  With film sources on various displays optimized for higher than 60Hz (i.e. front projector that support higher refresh rate), running the video at faster refresh rates also results in much better performance that eliminates some motion artifacts.  Most DVD material on the market today is film based (Motion Pictures shot on film) and therefore benefit from the use of PC based software decoders.  

DVD options available for the PC

Listed below are the most common software decoders:

PowerDVD
WinDVD
Cinemaster DVD
TheaterTek DVD

Our recommendations are that two software decoders be installed, and we prefer TheaterTek and PowerDVD.  This allows for an alternate software in case one fails with specific disk which can occur on occasion.  Scaling algorithms and decoding capabilities as well as user interface is some of the reasons for this recommendation.  

The second method is hardware decoding using a scaler card.  This method allows you to use a hardware decoder such as X-Card or a stand alone player fed into a video scaler card like Holo3DGraph.  This method is ideal for both film and video sources and can be employed in conjunction with niche products such as SDI modified DVD players.  The benefit of a scaler card is that you can also feed other NTSC sources such as VCR, cable/satellite STB, and LD players.