60Hz in, 48Hz out, stutter with subtitles

[ihan]

Hi,

A belated happy new year to everyone!

I have the VP50, and have been experimenting with 60Hz in & 48Hz out (via Arcam DV29 & Tosh HD-E1). The telecine motion judder disappears and the display seems to flicker a bit more. I understand this is the normal state of affairs.

My problem (or question) arises when subtiltles are enabled on either source. When each subtitle appears and disappears, there is a momentary stutter which lasts a small fraction of a second. This stutter is not present with 60Hz in & out.

What I want to know, is whether this is normal for any video processor doing 60Hz in & 48Hz out, or whether it is an issue with the VP50.

Regards,
Ian

[Avi]

Originally Posted by ihan

Hi,

A belated happy new year to everyone!

I have the VP50, and have been experimenting with 60Hz & 48Hz out (via Arcam DV29 & Tosh HD-E1). The telecine motion judder disappears and the display seems to flicker a bit more. I understand this is the normal state of affairs.

My problem (or question) arises when subtiltles are enabled on either source. When each subtitle appears and disappears, there is a momentary stutter which lasts a small fraction of a second. This stutter is not present with 60Hz in & out.

What I want to know, is whether this is normal for any video processor doing 60Hz in & 48Hz out, or whether it is an issue with the VP50.

Regards,
Ian

Hi Ian


What display are you using?

I use a Lumagen HDP to convert HD DVD 1080i 60hz to gen locked 1080p 48hz . The image motion is very smooth with no flicker on the Sony Pearl. I haven't used sub titles so can't comment on those.

AVI

[ihan]

I'm just using a 50PHD7 panasonic panel via the VGA socket.

Motion is very smooth, until any subtitles are enabled. I think somehow that the subs are causing the 3:2 cadence detection to falter, but I can't explain why or if this is normal for all processors with 60 to 48Hz conversion capabilities.

BTW, it does the same with 24Hz output as well.

[Steve_B]

not wanting to spoil the thread...or have much understaning in video proceesing..

why would you want to convert from 60 to 48hz...? what benefits does this give?

cheerss

[madshi]

Originally Posted by Steve_B

why would you want to convert from 60 to 48hz...? what benefits does this give?

Movies were originally shot in 24fps. Showing them in 60Hz means that you need to show the even frames twice and the odd frames three times (or vice versa). Repeating one frame twice and another one three times results in some stuttering being visible, especially on camera pans. Going 48Hz means that every frame is repeated exactly twice. This way the motion judder is gone.

Microsoft uses an iScan VP50 in their HD-DVD demo truck to convert the 1080i60 output of their HD-DVD player to 48Hz, so that their projector can show movies without any motion judder.

[The Nightfly]

Ian,

I've been using a VP50 for a few weeks now and have noticed some minor stutter problems on 60Hz material output at 48Hz. Not tried subtitles but I'm noticing it usually just after a scene change/transition, which may have some similarity to your subtitles on/off. Also, similarly, no issue when displaying at 60Hz other than the usual telecine judder.

I first noticed it with HD-DVD from the Xbox360 HD add-on. I made a posting to the main VP50 thread on AVS and got a couple of responses back from other Xbox HD users confirming what I'd seen but it seemed to be confined to being an Xbox 360 issue. Since then I've begun to notice the same thing with DVD from my Arcam DV27A using SDI. It's much less frequent with DVD, it happens maybe only 3 or 4 times in a whole movie but it's beginning to get annoying non the less.

I was beginning to put this down to 'bad edits' or something similar disk related, although I don't ever remember seeing this with the VP30 and DVD. I'm not sure now whether I'm just sensitised to seeing it after having the problem with the Xbox HD add-on or if this is a problem just with the VP50. Next time I've got the system fired up I'll give subtitles a go and see if the same thing is happening. Any particular disks you've tried?

Allan

[ihan]

Hi Allan,

It does seem like the same issue, looks like an additional 'force 3:2' setting may be required. Any 60Hz film material (both HD & SD) does it when I enable the subs with 48Hz output.

Thanks for replying, at least I know it isn't my vp50 that is defective. I don't use subtitles a great deal, but with some films, the dialogue isn't very clear (despite having spent a fortune on amps & speakers), so it would be good to get to the bottom of this.

Feel free to post this on AVS (if you can replicate the problem), as I'm not a member there.

Regards,
Ian

[Rob100]

Originally Posted by ihan

whether this is normal for any video processor doing 60Hz in & 48Hz out, or whether it is an issue with the VP50.

Just tried this using HD-A1 and 963SA SDI into Lumagen HDQ (using Fast and Furious HD-DVD and Revenge of the Sith R1 SD respectively) and there's no problem with 1080i60 from the HD-A1 and 480i from the 963 in and 1280x720 @ 47.952Hz out.

Looks like it's an issue with the VP50.

HTH,

Rob.

[ailean]

Won't the subtitles be generated by the player at 60fps (Video) where as the movie is 24fps with 3:2?

Sounds like a mixed mode kind of issue, especially if the subs aren't being generated frame locked to the original 60Hz film.

[ailean]

Had a play with this last night, watched some of ResEvil via an Oppo 971 SDI into the VP50 and out to the Sony Pearl (mmmmm very nice picture ).

With 1080p24 I eventually got the tearing issue in the bottom 1/4 of the image but it worked longer then my last try with T2. Again didn't notice any tearing with 1080p48.

With subtitles switched on the only thing I remember seeing was something I'd expect from my comment above, very occasionally as the text appeared or disappeared the text would seem to go interlaced. It would loose half it's scanlines as the DVD Player is generating 60 interlaced fps where as the VP50 is locking to the 24 progressive fps of the background film. So there's like a 1/5 chance that the appearance or disappearance will happen in a half frame.

There's not a lot of dialog in this film so I only saw this 3-4 times in about 40mins of watching.

I'm not as eagle eyed as some around here and not knowledgeable enough to say something else wasn't going on but the film itself seemed smooth, doing the pause/play trick with 24p tearing worked for a little while and I don't remember any tearing or possibly interlaced subs while in 48p (but like I said it was very occasional and most of the watching was in 24p).

[StooMonster]

ihan:

Are you getting tearing with the judder test pattern? I assume not as Panny plasma are good at 48Hz over VGA.

Sounds like a cadence failure 'Auto', it may be dropping in/out of video/film mode. It's highly recommended for inputs that are always going to be film (e.g. DVD player, HD DVD player, Blu-ray player) you select 'Film Bias mode'.

StooMonster

[ihan]

Yes, the 48Hz white bar judder test is fine.

I see the problem even if the deinterlacer is set to film bias mode (I suppose I should have mentioned that earlier).

[StooMonster]

Just reread your Original Post, are they electronic subtitles from a DVD player or are the in the film print?

StooMonster

[ihan]

Hi StooMonster,

They are electronically generated subtitles from a DVD or HD-DVD player. I'm now pretty certain that a '3:2' deinterlacing option would be an ideal workaround solution. Perhaps you could suggest such a thing to the DVDO guys?

Regards,
Ian

[Rob100]

Ian,

Just a follow up from my previous post regarding Lumagen HDQ.

Originally Posted by ailean

very occasionally as the text appeared or disappeared the text would seem to go interlaced.

I watched Crank R1 (using 963 SDI) last night and for no reason other than this thread I enabled subs for a while. I did notice something similar to this, but on no occasions did it cause the Lumagen to lose lock on the 3:2 sequence. The Lumagen does have a force film mode, but this did not prevent the occasional combing/interlacing of the subs.

Rob.