Anyway, this 576 lines thing...

[PJTX100]

I touched on this in the HD announcement thread, but it sort of got lost in all the excitement , so I'll have another go...

Regarding DVD as a source (realise a lot of you connect PC etc to the PJ)...

It looks like PAL DVD's output 576 vertical lines, 480 for NTSC

This seems to tally with me briefly seeing 576p or 480p info every time my PJ detects component input from the DVD

The guy in Richer who was convincing me about DVI-D was saying "but you are only getting 576 lines at the moment, with DVI-D it can be 720 and up"

My question is, if there's only 576 lines to play with, why bother using a connection which can carry more? The only advantage I can see, and it may be a noticable one, is that the D/A conversion in the DVD and the subsequent A/D conversion in the PJ is being avoided. But then DVI links (and HDMI I presume) are a bit iffy over large distances (7.5m +), sparklies etc.

If what I'm spouting here is roughly correct, I think I'll wait for me wanting to output a hi def source to the PJ before shelling out more wonga on a DVI/HDMI capable DVD player and a top end cable.

...or can you convince me otherwise? This is your challenge should you wish to take it!

...PJ

[pingu]

Originally Posted by PJTX100

The guy in Richer who was convincing me about DVI-D was saying "but you are only getting 576 lines at the moment, with DVI-D it can be 720 and up"

Just goes to show that these people know very little!

As you say, the main thrust of it is that the all digital transfer from DVD to PJ should lead to higher quality.

Also, some component inputs/outputs can carry hi-def material, but as it seems most HD content will be digitally protected you will need an HDMI / DVI(+HDCP) connection for it anyway.

I'm thinking of delving into the PJ scene this year, so am also concerned with apparent problems with long lengths of digital cable - anyone know more about this?

Cheers,
Steve.

[KraGorn]

PJ, you're right that the main reason for using DVI-D is simply to keep the video stream entirely digital, from source to display .. depending on the quality of the player and projector the difference between digital and analog component can be almost impossible to see, with other combinations you'll definitely notice the difference.

Also, when projecting on a large screen, say 80" or more, pixellation at 1024x576 starts to become visible and the image coarser as a result, hence you'd want to try to feed 720p into the projector from the player/scaler/HTPC.

I run a 9m DVI cable without a problem, the 7.5m 'issue' is with standard quality cables such as those from Lindy, while not cheap runs of 20m and 30m are available and longer than that you can use fibre.

[PJTX100]

Originally Posted by KraGorn

Also, when projecting on a large screen, say 80" or more, pixellation at 1024x576 starts to become visible and the image coarser as a result, hence you'd want to try to feed 720p into the projector from the player/scaler/HTPC.

Thanks KraGorn.
Regarding the pixellation point, I'm still a bit confused.
I would have thought that at some point (using component), I'm assuming in the projector, the 576 lines are being smeared across the 720 pixels (depth) to fill the screen. If the DVI allows the DVD to pump 720p straight into the PJ, is the "smearing" taking place in the DVD player then? At the end of the day the DVD disc is only 576 lines of information?...PJ

[SeaneyC]

Originally Posted by PJTX100

Thanks KraGorn.
Regarding the pixellation point, I'm still a bit confused.
I would have thought that at some point (using component), I'm assuming in the projector, the 576 lines are being smeared across the 720 pixels (depth) to fill the screen. If the DVI allows the DVD to pump 720p straight into the PJ, is the "smearing" taking place in the DVD player then? At the end of the day the DVD disc is only 576 lines of information?...PJ

Basically it's an issue of quality, and whether the projector takes the 576 lines and fits that to the 720line panel internally, or whether you get the DVD player to convert the 576 lines up to 720, before it sends it to the projector, where it will not be converted.

Clearly if the scaler (the gismo that takes 576 and outputs 720) in the projector is better than the dvd player, there is little or no benefit to buying the dvd player, but if the scaler in the DVD player is better, a clear gain can be seen by taking this route.

This is why HTPC is such a good option, as it can use all it's processing power to take the 576 lines and process it into 720 (aswell as other tricks you can do with it) which is generally far superior to almost all DVD players.

[Gary Lightfoot]

Don't say 'smearing', say 'scaling'!

Some DVD players can scale the 576 DVD up to 720 so matching the 1280 x 720 resolution of some projectors perfectly (Pioneer 868 for instance). If the projector is being fed 576, it will have to scale it itself in order to fill the panel. SOme projectors have better scalers than others, in which case an external scaler would show an improvement.

Gary.

[PJTX100]

Originally Posted by Gary Lightfoot

Don't say 'smearing', say 'scaling'!

OK, will do, not gonna argue with you Gary!

Originally Posted by Gary Lightfoot

Some DVD players can scale the 576 DVD up to 720 so matching the 1280 x 720 resolution of some projectors perfectly (Pioneer 868 for instance). If the projector is being fed 576, it will have to scale it itself in order to fill the panel. SOme projectors have better scalers than others, in which case an external scaler would show an improvement.

Gary.

Now this makes sense. Thanks all.

Just one more question (in the tradition of Columbo )

For a 2.35:1 DVD, are all the 576 lines used in the picture, or are the black bits taking some of the lines? I'm sure this is a stupid question, perhaps i've had too much !

...PJ

[Gary Lightfoot]

Originally Posted by PJTX100

For a 2.35:1 DVD, are all the 576 lines used in the picture, or are the black bits taking some of the lines? I'm sure this is a stupid question, perhaps i've had too much !

...PJ

Yes they are, and as you've surmised, the black bars top and bottom are encoded as if it were the rest of the image. All DVDs are 720 x 576, it's just how they should be displayed that's different.

A 16:9 DVD is basically a 16:9 image stretched upwards to fill the 4:3 area of 720 x 576, and the display will keep the height but stretch it sideways if it's a widescreen display.

If it's 2.35:1, the image including it's black bars are stretched up to fit, and the image and black bars are stretched sideways by the display.

Gary.

[LV426]

Quite. In fact, you might say that, because a DVD is a video medium, there is no such thing as a "2.35:1 DVD".

In terms of video signals, there are only two intended shapes - 4x3 and 16x9. So, it could be argued that all DVDs (in terms of their video signal) are either 4x3 or 16x9. Exactly. 16x9 video is also referred to as "anamorphic" and "enhanced for widescreen TVs".

In the case of a (very) widescreen film, in most cases, 16x9 video is used, and it contains the film, plus some black padding to get it to the right shape. So, it's perhaps better described as (for example) "a 16x9 DVD containing a 2.35:1 (or 22x9) film".

[PJTX100]

Originally Posted by pingu

I'm thinking of delving into the PJ scene this year, so am also concerned with apparent problems with long lengths of digital cable - anyone know more about this?

I only know that up to 7.5m seems to be the prevailing safe distance for DVI, though more expensive cables do claim to be good for lengths up to 20m...PJ

[KraGorn]

Originally Posted by PJTX100

Thanks KraGorn.
Regarding the pixellation point, I'm still a bit confused.

I see the discussion moved on later in the evening.

As has become clear, my reply presumed that instead of coarse pixels one instead has to deal with a softer image due to scaling .. it's a trade-off but after swapping projectors personally find a softer image less distracting than the coarser, un-scaled image.

[ozdvduser]

Originally Posted by PJTX100

I only know that up to 7.5m seems to be the prevailing safe distance for DVI, though more expensive cables do claim to be good for lengths up to 20m...PJ

I'm running a 10Mtr (33') DVI-D cable from Lindy that I imported from the UK some 1 1/2 years ago without any problems. You get what you pay for and their cables seem to be reasonably good quality.

[PJTX100]

Originally Posted by ozdvduser

I'm running a 10Mtr (33') DVI-D cable from Lindy that I imported from the UK some 1 1/2 years ago without any problems. You get what you pay for and their cables seem to be reasonably good quality.

That's interesting, thanks. Yes, Lindy do 15m and 20m too I think. When these HD DVD's take off, and/or I plan to upgrade one of my DVD players, I'll probably go for it.

Just blown the rest of my budget on a sub so it won't be for a while!!

...PJ

[KraGorn]

There have been a few forum members report problems using Lindy 10m cables, I had one that worked by it wasn't completely noise-free.

Whether these problems are down to the cable or an inadequate transmitter of course is unclear.

[PJTX100]

Originally Posted by KraGorn

There have been a few forum members report problems using Lindy 10m cables.

That's even more interesting.

I'll probably have to re-think the DVD player location if I go for this.

Thanks...PJ