Judder/Stutter...Scutter

Firstly lets make sure that I have my terms right, if not, please set me right

Judder: a momentary skip every five or ten minutes while the sound and video get them selves back into sync.
Stutter: Constant microskipping (often attributed to fitting 24fps into 60hrz refresh rate-but I really don't buy that explanation)
Scutter: collective term for all HCPC hardware/software

I have never noticed the phenomon described above as judder, scutter (and ofter words of a stronger nature) is a word I seem to be using alot since I got into this HCPC.

Stutter I see all the time. I have viewed three different projectors with a HCPC (Tosh MT3, Ae100 and a Hitachi data pj) and four different PCs varying in speed from a PIII 600 to an Athlon 1.7 and a P4 1.8. Windows 98, ME and XP. Powerdvd (three different versions), WinDVD, TT dvd players. And yes it's also there when viewing a movie on a monitor. So I conclude that this stutter is a part of HCPC. But I'm sure that most people on this forum have a more critical eye than I do so why does it not drive you all crazy.

BTW I have tried (I'm sure) everything under the sun to get rid of this.

Is this something that everybody lives with? does nobody else notice it? or is this a curse that follows only me no matter what PC, projector or monitor that I use?



Conor

 

Stutter: could be dropped frames , could be large mismatch between refresh rate of output signal and refresh rate of projector. ( most digital devices are 60Hz refresh)

I use theatertek on a 1.13GH tualatin system.Outputting at 60Hz to an ae100 (powerstrip for 1:1 pixel mapping). I only occasionally see microstutter . Most normal healthy human beings won't notice anything wrong.

 

Stutter - I run my HTPC @ 50HZ into my CRT projector, of course your display device may not accept this, but i don't know what refresh rates the devices you mention expect. I assume you know of the program Powerstrip to enable you to use custom refresh rates and/or display resolutions. (I currently 1024x576@50hz, hardly a standard windows resolution!)

The reason for this is my DVDs are all region 2, and when the film is transferred to the DVD, the 24 frames of film per second are mapped to 24 frames of video on the DVD, then the next second of film is mapped to the next 24 frames of video on the DVD resulting in a PAL DVD lasting 4% less than the original film. (Because difference between 25 and 24 is 4%). Purists would say this is a bad method, clearly, as all soundtracks etc are raised in pitch, and the film plays more quickly, but to be honest who notices it?

Running at 60Hz, you will run into errors when the computer has to start refreshing at a different rate to the inputted information. I believe this is what causes stuttering, but i could be totally wrong!

I use a (now feeble) Athlon 1Ghz with 640MB of ram with no problems at all. To be honest it was fine with 256, and i only upgraded for my video editing because my friend had some PC133 he was getting rid of.

If of course you're running region 1 DVDs then this is a wholly different prospect altogether, i will explain in detail if this is the case, and there are a whole other load of reasons why this may be happening.

I'm currently running Zoomplayer with windvd4 codecs, on XP with a Geforce2 mx, but will be "upgrading" to a "proper" htpc soon with a Radeon card and the new ravisent codecs.

I have never experienced any judder on my HTPC, but i guess i could be a number of things. I can throw a few ideas in that really cripple systems, task scheduler, screensavers, auto shut down of hard drives after 20 mins (power management).

Personally, switching from 60Hz to 50Hz when i got my projector solved all my stutter problems. If you don't have this option however i'm afraid i have no more advice. If your display device does not take 50Hz (my monitor said it was too low), try a multiple of 25, people have had great results with 75hz. Unfortunately my CRT PJ can't handle this, so i can't comment.

Hope this was of some help. Somone advise me if i'm blabbering again

 

Most digital devices are fixed 60Hz refresh AFAIK.

 

I'm running an HTPC into a Hitachi business PJ (CP-X325) which handles refresh rates up to 120Hz I believe. Tried running it at 75Hz and 100Hz and I still get noticeable stuttering on PAL DVDs running PowerDVD 4 XP. HTPC consists of P3-600, 256MB RAM, Radeon 7000, SB Live Value, running WinXP. It's not hideous - as in, I don't believe it's a lack of speed/power on the CPU/graphics front, but more likely an intrinsic fault with PowerDVD (I believe it happens with WinDVD as well, but will have to double check when I get home) or a refresh rate mismatch somewhere. Will have to experiment further, I suspect.

To me, it's bearable (just) but undesirable, and I'd really like to fix it.

BTW, I intend to try ZoomPlayer with the new Cinemaster filters, and see if that improves things.

Oh, one question - for NTSC DVDs what is the ideal refresh rate? I presume 60Hz should work fine? Cheers,

Dunc

 

Bear in mind that handling up to 120Hz might only suggest that the projector will only be able to handle these refresh rates it doesn't necessarily mean that the projector panel is refreshing at this rate ie it might well be resampling the incoming image before addressing the panel at 60Hz.

 

P3-600 could be a potential stumbling block, but IMHO there shouldn't be problems unless a lot of programs are running in the background. I know XP is a bit greedy if you have all the nicities turned on, i run it in the more classic look which seems to use a bit less CPU power with all window transition effects etc turned off.

As for NTSC discs, it depends whether the subject is film or video sourced. If it is video sourced, (Eg A TV series) then a multiple of 30 should be good. For Film source, a multiple of 24 is better because of the way the film is transferred to the DVD. I was going to explain, but realised i am not 100% on the process involved. Try a search on google for 3:2 pulldown. That will reveal all. It's all to do with getting 24 frames into 60 fields by duplicating certain frames and not duplicating others. It sounds complicated but it's really quite simple. I just can't explain it very well! Not so simple is getting the right picture (IE 24 frames) back out of the source, AFAIK this has a lot more to do with the codec used that the refresh rate.

120Hz is the best for NTSC sources as 60 and 24 are both factors. As for PAL & NTSC, i have no real solution.

THat's all the advice that this newbie has to offer

 

Keith,

That's interesting - it never ocurred to me that the PJ might not actually be displaying 120Hz when it says it is... Is there any way of testing this? I'll have to have a read thru the manual when I get home.

Seaney,

How do you know if a particular DVD player software is compensating for 3:2 pulldown or not? I didn't realise they could do this (silly me - just assumed it kept it at 30fps...)

As to my HTPC, I have it in Classic windows mode (it definitely improves performance) and have all tweaks & niceties off. I also avoid background programs, and shut down any that happen to be running before watching a DVD.

As I say, I'll have a play when I get home and see what I can see.

Thanks guys,

Dunc

 

Download Video2000 test program and run tearing test few times in a loop. http://www.madonion.com/products/video2000/

Usually digital projectors show terrible tearing at any other refresh rate than 60Hz.

 

Dunkyboy - I have NO clue as to how to tell if 3:2 pulldown is being performed correctly - Sorry!

I stick to my region 2 DVDs. (i've christened them in my mind as new High - Resolution DVDs after realising that Region 1 DVDs have 20% less resolution. Makes this poor student feel better after blowing loads of money on DVDs then finding out they've been out on region 1 for ages at a cheaper price.)

Still stuck in Reading at the moment but i can't wait to get back to sunny Edinburgh for more tweaking of the HTPC and prjector.....

 

Well, I had a play with the PJ last night and it definitely makes a difference switching the refresh rate between 72 and 60Hz when watching NTSC discs. I couldn't find any that are sourced from video, but when using film-sourced discs, 60Hz was quite nasty - so presumably 3:2 pulldown correction is being performed correctly by the software.

I must say, after considerable experimentation, the stuttering I mentioned really isn't that bad. It's only occasionally noticeable, and only when the image is panning at a certain slow speed. I think it may just be an inevitable part of 24/25fps video reproduction, and it's just more noticeable in progressive scan on an 8ft screen than it was on my interlaced 28" telly! After all, movies in the cinema can appear quite stuttery at certain points - I guess ideally we should aim for something a bit higher than 24fps, but somehow I don't see that happening in the forseeable future...

Just out of curiosity, what is the refresh rate of HDTV? Is it 30fps or something else?

Cheerio,

Dunc

P.S. - Seaney, Edinburgh is actually looking rather gorgeous today so maybe you'll be in luck when you return. On the other hand, we HT freakos like our weather grey and gloomy - less chance of light leakage spoiling our front-projected fun!

 

HDTV refresh?? depends on the format

1080i is 60Hz I think ?
720p not too sure about
480p is 30fps I think.

not 100% on this though

 

I would imagine that you are mentioning the wonderful HDTV system that the yanks use, i'm pretty sure that as it's still NTSC (ATSC is it's proper name i think) based, then it's 60hz for interlaced sources, and 30 for progressive. As for the system reaching our shores - doubtful. Have you ever seem a High res capable display for sale in the UK? (apart from projectors). Most of the plasmas that i've seen can't even resolve 540 lines properly, so that rules out 720p, 1080i and leaves just 480p (SDTV). My projector will only resolve 540p (1080i) and not 720p so i guess i'm just not really interested either! But it the price of those D-Theatre machines came down who knows........... Glad to see that your region 1 stuff is working better at 72Hz. I'll stick to my cherished hi-res region 2 ones....

Also what PJ do you have? In your setup i can only see your baby TV listed. I have to admit i've never seen a decent DLP so cannot comment on the "rainbow" effect so many people talk about. I'll stick to "old faithful" (my CRT PJ), apparantly it was used on some program called the golden shot (maybe 50 hours use) but this is WAY before my time, i'm only 20! Now to build up my DVD collection as i have finally upgraded my stereo to a point i feel happy at. Last day at work. Here i come Edinburgh!

 

comer

a few questions...

did you still see microstutter with your xcard via vga\component?
do you see it with your radeon @640x480?

I agree with your comments about stutter, with powerxp, windvd + gf3 I could see it all over the place, even with the theatretek ravisent decoders I could still see stutter.

my mpact2 @640x480x16bit is smooth though, I think as its hardware based and I run it at its lowest resolution, anything above that and I see stutter.

I think it depends on how your eyes pickup movement, ie to many dlp is the way to go, I can't watch the image as I can tell its flickering.

I know a few guys have given up the htpc route and gone for prog scan dvd players with good results.

a route I will take....eventually.

john

 

Hey John

I'm like a broken record with this stutter thing.

I sold my xcard so that is no longer in the picture. Running the radeon card at 640X480 @16bit has eliminated any tearing, and reduced the stutter but it's still there. That said I now see stutter everywhere, on TV (mostly on cartoons and on the discovery channel) so perhaps I'm just too sensitive to it. It doesn't really bother me since I got rid of the tearing and at least now I know that it's not the projector.

Tell me more about this mpact2 card, can u point me to a link for it with specs and prices.

Thanks for all the replies, I'm convinced that alot of people have stutter, but the lucky buggers don't notice it. Maybe someday I'll get to the bottom of this, in the mean time I'm enjoying the big screen experience more than I ever did before (since reducing my res. to 640X480)


Conor

 

It is possible to get rid of judder, stutter and scutter as long as it's not in the source material and you use a CRT projector (or monitor), the correct refresh rate and a scaler/HTPC solution that doesn't introduce any of the above problems. I never achieved 100% stutter free with software players (got close), but I finally managed it using DScaler, an SDI capture card and an external SDI DVD player.

 

I thought VHS (that is what you were referring to, right?) only resolved about 200-odd lines?

 

comer

mpact2 agp card info :
http://www.digitalconnection.com/mpact2.htm

It's discontinued now but was highly sought after in it's time (esp by crt lovers) and can still get a decent value 2nd hand.

As an all-in-one solution its great, you get the mpact2 agp vga card with mpeg2 decoding/vga/svid/composite + spdif/stereo on the same vga card, the dvd software is included.

They were developing the mpact3 but they (chromatic)got bought by ati so it was halted and I don't think they could sell enough mpact chips to make it worthwhile either.

I bought mine through the forums a few months back after trying to get my gf3 to run smoothly. Its has had its low pass filters removed which apparently improves the image no end, very difficult to do with the m/b version.

with your 10 mins of xcard experience did the image microstutter or was it smooth??? can youremember that far back?

john

 

Ahhh, interesting. So.. the 200-line thing was actually referring to the approximate number of pixels along the horizontal aspect of the image, if the VHS image was actually represented by pixels.

I just thought it was referring to the fact that although the VHS output will be 576-line PAL, the detail resolution that is actually produced will only be approx. equivalent to 200-odd lines, just because the format isn't really capable of resolving all of the PAL scan lines.

Okay, now I'm just confusing myself...

Cheers,

Dunc

 

I used to have a small problem with a slight jump / jitter every minute or so but last night I changed my player to the new nvdvd player from nvidia.

What a difference! I find an improved quality of picture with no skip or jitter. Still a slight jerk on slow smooth pans but thats something i think i will always have.

Hope this may help some of you with geforce/nvidia based cards!

 

ninc0,

Where did you download NVDVD?

It don't seem to be available on nVidia's site.

Wouldn't mind having a look at it.

 

got it on kaza site, same place you can download mp3's