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[Doof]

Anybody know what's required to build an JRMedia Center centered HTPC that's capable of progressive scan / HD upconverting DVD playback? Is it just a particular DVD drive that's required? Software?

[jmone]

It really comes down to the video card, its drivers (and the filters).  The card can only output one resolution at a time, so your HTPC will end up scaling content to whatever you have selected (I'v got mune at 720p which scales some stuff up and some stuff down...it just looks the best on my mid price plasma)


In selecting a video card, how do you plan to;
- connect to AV equipment (eg HDMI/DVI, Component, VGA D-Sub for Video, and also sound, HDMI, S/PDIF, Analogue etc)
- What resolution do you want to run (eg what looks best on your TV).

Card selection is important as they have different issues.  I'v used nVidia (poor) and Intrl G33 (better) but have heard ATI is pretty decent.

Nathan

[glynor]

I like my ATI cards for HTPC use.  Nvidia's newer stuff is pretty good as well, but generally you can't go with their cheap, low-end parts.  The mid-range is the sweet spot for both vendors, though AMD/ATI tends to scale a little better (HTPC wise) on the low end.

If you're looking for a new card, I'd probably wait a tiny bit right now, as AMD and Nvidia are both gearing up to launch new midrange parts at the end of this month or the beginning of next month.  AMD is launching their new RV670 GPU (expected mid-November with a sub-$250 price tag) and Nvidia is launching their 8800GT card late this month or early next with a $250 price tag.  For now, it looks like in 3D performance the AMD card is winning.  They'll likely be somewhat equal in video-related capabilities.

[Doof]

So the gist I'm getting is that progressive scan capability is just a function of the video being output by the device, correct?

[jmone]

Correct, you will pick a resolution and the PC (CPU / Vid Card / Drivers / Filters) will do the required scaling & deinterlacing - the Q will be how good it is at it!

[glynor]

So the gist I'm getting is that progressive scan capability is just a function of the video being output by the device, correct?

Mostly.  All CRT TVs are interlaced, and all computer displays are progressive.  The trick is that (because the standard was designed for interlaced CRT TVs) all DVDs are interlaced.  No ands, ifs, or buts.  It's part of the standard, and it is the only "DVD-Video Compliant" way to put video on a DVD.

What a "progressive scan" DVD player does is reconstruct the original progressive film frames out of the interlaced content on the DVD disc.  It does this because it knows what "magic" trick is used to convert 24 frames per second film (progressive obviously) into ~60 fields per second (interlaced) video (called Telecine 3:2 Pulldown) when creating the DVD.  It then just does the reverse of this process to reconstruct the original progressive 24 fps video (called Reverse Telecine).  This, of course, only applies to video that was "originally" recorded as progressive.  A progressive scan DVD player cannot magically turn a DVD that was encoded from interlaced (video usually) source content into a "true" progressive video.  What it does then depends on the player, but most run the video through a "de-interlace" procedure, which adds varying smartly-applied amounts of blur to mask the interlacing artifacts.

NOTE: I'm actually simplifying the process in some ways and making it more complicated in others... Most modern DVDs actually have true 24fps video on disc (when sourced from film anyway).  It is still interlaced, but since it is 24fps "native" it doesn't have to do reverse telecine to reconstruct the frames, it simply ignores the normal "flag" to reconstruct the 54.94 (60i) fields per second video stream and displays field 1 and 2 for each frame simultaneously.  However, many DVDs that were created from video source rather than re-scanning the original film (which is more of them than you'd think because scanning film is expensive) still use Telecine 3:2 pulldown.

If you want to learn more about how 24fps progressive footage is embedded in 59.94 fields per second interlaced footage check here: http://www.dvdfile.com/news/special_report/production_a_z/3_2_pulldown.htm

Because all computer monitors are progressive scan, video card vendors have developed detection algorithms that detect this 3:2 pulldown being displayed and then do a "Reverse Telecine" on the video to restore the progressive footage and incorporated this technology into both their hardware and their software.  Different vendors have varying degrees of success.  Also, some DVD Playback applications also have this feature built in (though the proper place is really in the decoding DirectShow filters).

Generally, AMD (ATI) has the "best" pulldown detection.  However, for standard 24fps film --> NTSC DVD playback (reverse 3:2 pulldown) both Nvidia and AMD's systems work perfectly well.  It's only when you get into the weirdo Anime framerates and pulldown patterns (such as 3:2:2:3) that AMD's filters are a bit better than Nvidia's PureVideo.

[jmone]

Isn't Telecine / Reverse Telecine actually used to recreate a 24fps from a 29.97 fps NTSC feed and can be done on both Progressive and Interlaced content?  The PC it self will the use on of the deinterlace techniques (eg BOB) to combine the feilds into frames.
Thanks
Nathan

PS In the PAL world we don't tend to use Telecine during the 24fps film to 25fps video conversion, they just run it 5% quicker!

[glynor]

Isn't Telecine / Reverse Telecine actually used to recreate a 24frames-per-second (fps) from a 29.97 fps NTSC feed and can be done on both Progressive and Interlaced content?  The PC it self will the use on of the deinterlace techniques (eg BOB) to combine the feilds into frames.
Thanks
Nathan

Telecine 3:2 Pulldown is used to embed 24fps video into standard NTSC/ATSC 54.94 fields-per-second video (which is the same thing as 29.97 frames per second or so-called 60i video).  Note, fields vs. frames.  29.97 is actually a misnomer because there is no such thing as a full frame of content in interlaced video.  There are only fields evenly spaced in time.  We think of them in frames because it is easier to think about 1/2 frames than these odd half-resolution fields.  In reality though field 1 is equally spaced from field 2 which is equally spaced from field 3 and so on.  The video signal doesn't know or care about the "virtual" frames.

Reverse Telecine is used to reconstruct those original progressive frames.

Telecine is actually the name of the physical film-scanning machine that does this process.  There are many different "types" of Telecine processes.  3:2 pulldown is just the most common because it is used to convert 24fps to 60i.  There are others though.

And, yes, PAL is better.  NTSC is older though, so it's no surprise that it's stinkier.  However, the downside to PAL is that you never get to see a film at it's original "intended" speed.  Ever.