castleinthesky wrote:Could someone please explain to me what HD DVD will be, and how much different it will be from DVD?
castleinthesky, just as DVD (Digital Versatile Disc) was a 5" disc that was "bigger" (had higher capacity or "space") than CD (Compact Disc), some form of HD (High Density actually) DVD disc will eventually replace it. CD has 0.650 GB (gigaBytes) of space. DVD has 9 GB of space. Right now theres no HD DVD standart, but there are two main "contenders" for it.
CD as a consumer format is mainly used for music.
DVD is mainly used for video (tho there are Audio only variations like DVD-Audio).
Altho DVD has great storage space, the 9 GBs wasn't enough to store digital video, so a video compression codec called mpeg2 was used to store 2 or more hours of standart definition (SD) video. mpeg2 compresses video about 15 to 30 times to gives us the DVD quality video we have now today. In the US and other NTSC TV standart countries that video is 480 pixels tall by 720 pixels wide in quality. In Europe and other PAL TV standart countries that video is 576 pixels tall by 720 pixels wide. On average we would say this is 500 line video, as the average height is about 500 pixels rounded.
You could use your computer's screen height resolution as a comparision stick
HDTV (High Definition) encompasses a series of higher quality formats that vary in size, but are mainly one of two: the 720 pixel tall by 1280 pixels wide one, or 1080 pixels tall x 1980 pixel wide one. So we could call those about 700 line and 1000 line video. HDTV has also the chracteristic that it was designed from conception as 1.78 wide (16:9) as opposed to the old analog TV standarts that were 1.33 wide ("4:3")
The future HD DVD disc format (or formats), having much higher capacity than current DVD, would easily accomodate this higher resolution video.
The 2 main contenders are AOD (Advanced Optical Disc) which will have a maximum capacity of 32 GB. It has recently been called HD-DVD by its proponents, so most people think it's THE HD DVD, but that remains to be seen. The other one is Blue-Ray DVD (BD-DVD?) which uses a more advanced blue laser so it will have a maximum capacity of 54 GB.
As you can see these higher capacity discs by themselves can store video thats 3.5 to 6 times higher in resolution than current DVD using the current mpeg2 compression. But now there's also "new and improved" mpeg4 compression, which has different "names" or "flavors" depending on its variations and pedigree. Microsoft's version is the one used in WM9, then there's the mpeg4 consorcioum's own H.264/AVC that was ratified by the DVD Forum and is part of Quicktime (as Quicktime is basicaly the same as mpeg4), and the independent 3ivX, DivX5, xviD, etc. Those codecs, being more efficient, can further compress the video up to 3 to 6 times more than current mpeg2 with the same quality results.
At present time AOD has chosen mpeg2, H.264/AVC, and VC-9 as codecs, and Blue-Ray mpeg2 and H.264/AVC
So adding 3 to 6 times more compression to 3.5 to 6 times more capacity, make possible a whopping 10 to 36 times higher resolution HD DVD format, which could accomodate 700 line HDTV, 1000 line HDTV, and BEYOND: 35mm film quality (1200-1500 lines, some much wider than 1.78 wide) and up to 70mm quality (2000 lines) if they wanted to. (You can see some film format quality numbers in my previous post
)
When will this happen and how it will happen has yet to be determined. The AOD camp, promising quicker implementation usually talks about the 700 line, lowest quality one the most...
Hope you have a better idea now of what HD DVD might (or might not) be.
