1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Anyway, this 576 lines thing...

Discussion in 'Projectors, Screens & Video Processors' started by PJTX100, Jan 10, 2005.

  1. PJTX100

    PJTX100
    Well-known Member

    Joined:
    Dec 21, 2004
    Messages:
    8,140
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +564
    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! :D

    ...PJ
     
  2. pingu

    pingu
    Active Member

    Joined:
    Nov 30, 2004
    Messages:
    440
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    28
    Location:
    Berkshire
    Ratings:
    +28
    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.
     
  3. KraGorn

    KraGorn
    Active Member

    Joined:
    Aug 30, 2003
    Messages:
    4,745
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    68
    Location:
    Warrington
    Ratings:
    +27
    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. ;)
     
  4. PJTX100

    PJTX100
    Well-known Member

    Joined:
    Dec 21, 2004
    Messages:
    8,140
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +564
    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
     
  5. SeaneyC

    SeaneyC
    Active Member

    Joined:
    Jul 26, 2002
    Messages:
    2,031
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    48
    Location:
    Reading, Berkshire
    Ratings:
    +54
    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.
     
  6. Peter Parker

    Peter Parker
    Distinguished Member

    Joined:
    Apr 6, 2001
    Messages:
    13,152
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    UK.
    Ratings:
    +2,671
    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.
     
  7. PJTX100

    PJTX100
    Well-known Member

    Joined:
    Dec 21, 2004
    Messages:
    8,140
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +564
    :oops: OK, will do, not gonna argue with you 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 :beer: ! :)

    ...PJ
     
  8. Peter Parker

    Peter Parker
    Distinguished Member

    Joined:
    Apr 6, 2001
    Messages:
    13,152
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    UK.
    Ratings:
    +2,671
    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.
     
  9. LV426

    LV426
    Administrator Staff Member

    Joined:
    Jul 14, 2000
    Messages:
    13,383
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Somewhere in South Yorkshire
    Ratings:
    +5,770
    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".
     
  10. PJTX100

    PJTX100
    Well-known Member

    Joined:
    Dec 21, 2004
    Messages:
    8,140
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +564
    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
     
  11. KraGorn

    KraGorn
    Active Member

    Joined:
    Aug 30, 2003
    Messages:
    4,745
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    68
    Location:
    Warrington
    Ratings:
    +27
    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.
     
  12. ozdvduser

    ozdvduser
    Active Member

    Joined:
    Apr 21, 2003
    Messages:
    170
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Location:
    At The Track or Melbourne Victoria Australia
    Ratings:
    +3
    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.
     
  13. PJTX100

    PJTX100
    Well-known Member

    Joined:
    Dec 21, 2004
    Messages:
    8,140
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +564
    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
     
  14. KraGorn

    KraGorn
    Active Member

    Joined:
    Aug 30, 2003
    Messages:
    4,745
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    68
    Location:
    Warrington
    Ratings:
    +27
    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.
     
  15. PJTX100

    PJTX100
    Well-known Member

    Joined:
    Dec 21, 2004
    Messages:
    8,140
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Ratings:
    +564
    That's even more interesting. ;)

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

    Thanks...PJ
     
  16. KraGorn

    KraGorn
    Active Member

    Joined:
    Aug 30, 2003
    Messages:
    4,745
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    68
    Location:
    Warrington
    Ratings:
    +27
    Maybe Lindy's quality has improved, I'm going back 12 months or so when projectors like the Z2 first came out and helped popularise DVI connections .. that said, I bought a 5m Lindy not long ago and didn't notice any difference from ones I was buying 12 months ago.
     
  17. JohnWH

    JohnWH
    Active Member

    Joined:
    Jan 23, 2004
    Messages:
    1,826
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    48
    Location:
    St Albans
    Ratings:
    +82
    Think it depends on the source and sink device as much as the cable. I can use the 10m lindy cable fine when feed from a samsung DVD into a Z200, but when I connect a PC I start to get a small amount of intermitant dropout. This may also be resolution and refresh dependent as well...

    John.
     

Share This Page

Loading...