http://www.crtprojectors.co.uk/sdi_dvd.htm
Q: So why do I need SDI?
A: SDI* is 4:2:2 YCrCb component video, exactly what comes out of a DVD players MPEG decoder.
The point of having a DVD player with SDI output is to remove one D/A* conversion and one A/D* conversion in the video chain to a scaler. For a scaler to de-interlace and scale interlaced video it must work in the digital domain, in a normal DVD player the digital signal from the MPEG decoder must be converted to analogue video to be output as component video then digitised again as soon as it arrives in the scaler for processing. By adding an SDI output connected directly to the MPEG decoder a pure 4:2:2 YCrCb signal can be sent straight to the scaler with no D/A or A/D conversion. This means no D/A or A/D conversion artefacts, higher frequency response, less picture noise, reduction in visible edge enhancement** and much improved colour saturation and purity. All this does require a scaler with an SDI input, check the Crystalio or Plasma Enhancer Pro scaler and get some of the best DVD images you will ever see. It is also worth noting that SDI carries no encryption or copy protection, DVI / HDMI does, SDI is just the raw digital picture information straight off the disc in the form that broadcast studio's have used for many years.
* SDI = Serial Digital Interface. A/D = Analogue to Digital conversion. D/A = Digital to analogue conversion.
** Edge enhancement is added to DVD's during the authoring stage to make them appear sharper than normal, this is fine on a regular 28" TV but results in ghostly white halos round objects on screen when the image is much bigger. Edge enhancement is normally made worse by D/A and A/D conversion to the point where some DVD's look terrible. SDI cannot remove what's on the disc, but it can stop it being made worse.
Note: SDI modification of lower cost DVD players tends to produce a bigger relative increase in performance than modifying high cost players. The reason is simple, high cost players may have up to 14 bit 216Mhz D/A conversion that's extremely good, in other words the players analogue output is also very good. Lower cost players may have 10 bit 54Mhz or 12 bit 108Mhz D/A conversion which is not so good, SDI modification of these players can produce quite startling results, because SDI modification takes the D/A converter out of the video chain. You still remove the need for A/D conversion into a scaler with any SDI modification, but the relative gain is often more on lower cost players.
Note: For trouble free SDI performance use only 3Ghz rated cable. We use, sell and recommend Belden 1865A, or Liberty Interflex-SD for longer runs / noisy electrical environments. See bottom of page.
Many SDI related problems can be caused by use of poor specification coaxial video cable, avoid image flashing and other related issues by using only 3Ghz rated cable. SDI is a very high frequency digital signal. Correct cable specification theoretically allows SDI to be robust enough to work with cables up to 300 meters long. If you have problems with a 1 or 2 meter cable, change it for the correct type below.
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