Progressive scan from a PC - need the facts

[Steve MF Lai]

If one plays a DVD from a PC DVD ROM set to 800x600 at 75Hz, does it mean that one is getting 600p at 75Hz.

If one sets the PC display to 1600x1200, does this mean the one is now getting 1200p (progressive scan at 1200 horizontal lines ?

Does this mean that the quality of the movie quality is better at 1200p, assuming all else is the same ?

Has the refresh rate any meaning when the output goes to a LCD or Plasma screen ? I was told that refresh rates are only applicable to CRT based TVs or monitors.

Can someone help clarify ?

[cjb110]

not sure about the progressive scan issue but I do know that refresh rates are an issue on LCD/TFT screens.

The PC based LCD/TFT screens can have poor refresh rates so anything that moves fast (games/dvd) can break up into a mess of digi corruption.

Plasma's don't have this problem, either cause their refresh rate is high enough or that the technology works different:)

about the pscan, have you tried it? and can you see a difference?

[Steve MF Lai]

There are some dark secrets here that mfrs are not prepared to speak out or it is in the domain of the ultra specialist.

Reasoning from simple physics, I believe that LCD & Plasma are switchable as a combination of individual pixels. Hence they can be "on" or "off" at any time anywhere on the screen. CRT based TVs & monitors cannot because a "pixel" is only "on" when the electron beam hits the phosphor spot. Hence in CRTs the pixel can only be switched "on" by the e beam. Therefore CRT has refresh rate issue & LCD/Plasma should not.

However, if during use eg PC DVD ROM playing DVD movies there appears to be pixelations etc, I believe this could be due to

> slow CPU & low RAM on board
> software based decoder that not good or fast enough
> poor mpeg 2 material

or a combination of these problem. Some of these problem can be solved by using an addition PCI hardware mpeg2 decoder I was told.

At this point I can say that it is diffcult to pick out the difference in picture quality overall between PC DVD ROM output (progressive)and DVD player + iScan line doubler (that outputs progressive scan & double the lines). My display is a Panasonic 42" plasma screen and the test DVD movies are Super Speedway (Mach II special addition), Independence Day & the Abyss.

Of course the PC DVD ROM is a cheaper solution for me.

[cjb110]

mmm, sounds ok, but has the video format was designed to be displayed line by line, wouldn't the technology in the plasma/lcd work in a cycle from top to bottom? so it would have a refresh rate of sorts...not sure though

As for PC hardware decoders, I would be careful and test first.

I have a hollywood+ card and that produced worse results than PowerDVD. Neither of them had playback problems, it was just that the picture was much better on PowerDVD. (the system was a PIII 800, 256Mb) Plus the card had problems with the the menu systems, the overlay graphic that should show which item you've selected, was often garbled and in the wrong place. (but this could be a driver issue, which was another problem, they didn't update the drivers reguarly enough, and I doubt the XP ones are gonna be out anytime soon)

[Steve MF Lai]

Thanks for the tip on Hollywood+ decoder. I have been thinking about whether I get better quality this way although I am getting pretty good quality pictures fr Intervideo 2000.

With the convergence of TV & PC, I was wondering if the TV tuner cards will be a better way to go. Some of these cards are designed to provide higher progressive scan output.

[cjb110]

Yea TV cards seem like a good solution, I would be careful of Hauppage, again I had one, and although the hardware was good, the drivers and the software where very very poor.

But that was a good 3 years ago, so hopfully they've changed.

Both hauppage and ATO do cards with built in tivo/replay style functionality...so that would be a bonus, considering most of the standalone designs come with pointlessly small 40Gb hard drives, where the pc could easily be kitted out with 3*80Gb...or more via the scsi route.

The (hopefully announced and confirmed soon) Thompson Sceninum, DVD+RW with tivo functionallity as well sounds like a great idea. record everything, keep the good stuff.

[Steve MF Lai]

Thanks, will keep a lookout for the Thomson product.

Incidentally I have built a RAID system (RAID card - about 100 pounds sterling) with cheaper 5,400 rpm disk drives. This is a cheaper way than getting into SCSI. The RAID system is used in Servers and they are really quite good for video editing & related work that needs sustained data throughput.

[cjb110]

yea forgot about that solution :)

I'm gonna have to find out how much spec a PC based tivo would need. We've got a old system acting as a internet gateway in the front room, we could easily connect our blueyonder cable system to a suitable card...but as its quite old, were not sure if it could cope...oh well some fact hunting to do:)