CurtPalme.com Home Theater Forum

lexx21 · Joined: 10 Oct 2008 Posts: 119

I was sort of curious about what the benefit would be to running my dwin 700 at 72hz for 1080i instead of 60hz. Would this be stretching the limits of reality with what I can do with this projector?

**kal** · Posted: Fri Jul 17, 2009 12:08 am Post subject:

If your Dwin can scan to at least 41Khz (which it seems it can as it goes to 65Khz from the specs I checked) then going with 72Hz instead of 60Hz will get rid of what's called "3:2 pulldown" or "inverse telecine" which is a process that is used to convert 24 frames/sec film to 60 frames/sec (or Hz) video.

See: http://en.wikipedia.org/wiki/Telecine

24 doesn't fit into 60 nicely so the trick is to show some frames more than others. The result is called "judder" which looks like image shake/instability.

It bothers some people so they run their displays at multiples of 24 (48, 72, or with some new digital displays, 120Hz).

I can see it if I look for it and it shows up more in smooth slow panning shots (like the slow downward pan in the opening of Shakespeare in Love) but frankly I think most people blow it out of proportion.

I ran 72Hz (or 71.928Hz to be exact) for years when I played DVD's on my HTPC but since I went to Blu-ray a couple of years ago I'm doing 60Hz and frankly don't even notice. With HTPC's it's easy to do so why not do it. With regular sources you need some sort of fancy scaler/video processor.

How were you planning on doing 72Hz anyway? What source?

Kal

lexx21 · Joined: 10 Oct 2008 Posts: 119

I have a dvdo vp30 scaler that will allow me to do 72hz output. My input sources are a toshiba hd-dvd, samsung blu-ray, htpc, and hopefully soon an oppo region free dvd player.

perisoft · Joined: 29 Aug 2007 Posts: 2920 Location: Ithaca, NY

Oh, man... do 72hz. It makes a HUGE difference! *looks at kal suspiciously* Smile

**kal** · Posted: Fri Jul 17, 2009 12:47 pm Post subject:

I would certainly try it if you have everything already to do it.

Kal

Mark_A_W · Posted: Fri Jul 17, 2009 1:48 pm Post subject:

Yeah...what are ya blind Kal?

Actually, I've noticed that not all sources do 60hz the same. My mate's HD-DVD player was much smoother than his HTPC at 60hz. But the HTPC at 48hz was smoother again.

**kal** · Posted: Fri Jul 17, 2009 2:25 pm Post subject:

Nope, not blind.

We've been running 60Hz for what? 50 years now? Only recently have we started to see consumer TV's that support 120Hz (an even multiple of 24 and 30 - the refresh rates of film and video). The public hasn't been complainint for 50 years.

I still think the difference is blown out of proportion and even when the difference is seen, it's very rare occurances.

Kal

Kiev Savoie · Joined: 25 Oct 2007 Posts: 432

[quote="kal"]The public hasn't been complainint for 50 years.
[/quote]

In all fairness Kal. Half the public couldn't tell the difference between SD and HD. I've literally been asked before, "So is this HD?"! After I hooked his flat panel up correctly I said "Yes". I even offered to calibrate the colors on his display with a DVD that had the THX freebie calibration tool since the colors were garishly over bright. He said, "what for? looks OK to me."!

Rolling Eyes

**kal** · Posted: Fri Jul 17, 2009 2:58 pm Post subject:

That's very true.

I was just surprised myself after having run an HTPC at exactly 71.928Hz for years for DVD playback that I didn't notice anything much in terms of judder when going to a PS3 to play Blu-ray/DVD.

Kal

ecrabb · Posted: Fri Jul 17, 2009 3:04 pm Post subject:

Kal, I forget - Do you run 1080i or 1080p?

Running 1080i/60 will diminish the effects of judder somewhat vs. running 1080p60.

I too think the effects of judder are overblown. I run 1080p/60 from the PS3 and rarely notice judder. Only very certain instances. We're talking MAYBE 5-10% of a typical movie, and much less if I'm not specifically looking for it.

SC

**kal** · Posted: Fri Jul 17, 2009 3:05 pm Post subject:

I ran 720p/71.928 on the HTPC and on the PS3 am now running 1080i/60.

Kal

Kiev Savoie · Joined: 25 Oct 2007 Posts: 432

It's one of those little details that some people who are perfectionist enough will spend the time and money to tweak and others won't bother.
Lexx, I'm going to agree with Kal. if you already have the equipment to do it and you like to experiment with your setup, why not? you might learn something. Unless I already had the equipment though, I would not bother either.

ecrabb · Posted: Fri Jul 17, 2009 3:15 pm Post subject:

Oh... I can't believe nobody has mentioned this, but running 1080i at 72hz isn't really solving anything. It will appear smoother than 1080i/60 at a glance, but not only will you still have judder (though it's smoother judder), you're actually going to be displaying two film frames mixed together every other film frame!

If you want film frames displayed perfectly both temporally and spatially, you should either run 1080p @ 24/48/72, or 1080i at 96.

SC

Kiev Savoie · Joined: 25 Oct 2007 Posts: 432

What about 1080i at 24? that must work pretty well besides the flicker issue?

ecrabb · Posted: Fri Jul 17, 2009 3:23 pm Post subject:

1080i/24 would only give you 12 progressive frames. You mean 1080i/48? Yeah... I guess that would work if you could stand the field flicker. Never tried that one.

SC

Kiev Savoie · Joined: 25 Oct 2007 Posts: 432

Oh, gotcha 24Hz = 24 passes of half the scan lines interlaced. Duh Embarassed

Mark_A_W · Posted: Fri Jul 17, 2009 11:32 pm Post subject:

Mark_A_W · Posted: Fri Jul 17, 2009 11:35 pm Post subject:

lexx21 · Joined: 10 Oct 2008 Posts: 119

"sticks out like dogs balls"... ROFLMAO!!!!!