Quick question about 480p and DVDs (1 Viewer)

[Chris_S]

I am new to the whole HDTV stuff. I just got an HDTV a few weeks ago. A couple of things I've noticed is on DVDs there is a little saturation or grain in certain scenes of DVDs in bright spots. Is this because of compression or am i picking up interference from something? Just wondering.

Could someone answer me this?

 

[Michael Reuben]

It's impossible to answer without talking about specific DVDs. What you've described is so generic that it could be caused by any number of factors (including the intended look of the source material).

I'm not sure why the title refers to "480p".

M.

 

[Chris_S]

I have a JVC 48wp30 HDTV. My DVD player is a XV-N50BK. The DVD's are American Beauty for one. One scene where Spacey is talkin to that "Brad" guy at the beginning of the movie. The wall behind Spacey has a small fuzziness about it. Some movies have this same affect. Everything looks great except for a few spots like that.

Hope that helps. Also the reason 480p is in the title I thought maybe it was just because of progressive scan and seeing the screen bigger.

I don't really see it in anything other then 480p.

 

[Neil Joseph]

I don't have American Beauty so I can't comment on that. When you switch over to 480i are you saying that the "grain" disappears?

 

[Chris_S]

The grain is not as noticable. I sometimes think I am just being over critical.

 

[Robert_Barlow]

It is also possible that your television has a better line doubler then your DVD player. That could be one reason why the 480i picture looks better(thats how it was explained to me anyway).

 

[Bob McElfresh]

It is also possible that your television has a better line doubler then your DVD player

Well... most DVD players dont have line-doublers. They have other circuitry like 3:2 pulldown and some other stuff. But DVD's contain and produce only 480 lines. (Yes, there is a Samsung DVD player that will do up-conversion to 720/1080 - but it is the exception.)

DVD Video IS compressed and sometimes the un-compression in a DVD player has problems with lots of fine-grain patterns. Some classic problimatic scenes are:

- The begining of The Fifth Element on wide shots of the stairs leading to the tomb. The lines in the stairs would break-up/rainbow fairly badly.

- In Twister, Bill Paxton wears a Houndstooth jacket with lots of small, black threads that often cause grain/artifacts.

Different brands of DVD players solve these problems differently.

 

[Chris_S]

Thanx Bob. I think that's what it is. The way you explained it pretty much sounds like what I got. Not a big problem just notice it sometimes. I'm just anal and never truly satisfied with any picture no matter how great. Always looking for it to be better.

Thanks again

 

[Allan Jayne]

>>> most DVD players dont have line-doublers...

I am not sure whether this is true, but if it were, then there will be many instances when a TV's line doubler will give better performance than the DVD player's 3-2 pulldown sensing. The player needs a good de-interlacing doubler to fall back on if the 3-2 pulldown is absent, not perfect or incorrectly flagged on the DVD.

Video hints:
http://members.aol.com/ajaynejr/viddoubl.htm

 

[Bob McElfresh]

Well think about it: standard video is 480i. Progressive DVD players produce 480p.

Where is the line-doubling if the lines of video are the same?

 

[Allan Jayne]

The 3-2 pulldown flag sensing and frame re-assembling mechanism that progressive DVD players have (should have) can be thought of as a de-interlacer (loosely called a doubler) in that interlaced video (480i for NTSC) always coming from the player's MPEG decoder goes in and progressive video (with twice as many scan lines per second) comes out.

The problem is, if the only de-interlacing mechanism is that one, should the flags on the DVD be absent or incorrect, frames will be assembled in a fashion that leaves much to be desired subject matter wise, although they are still 480p.

So good DVD players often have the same de-interlacing chips inside them that TV sets and stand alone de-interlacers may have, including Faroudja DCDI chips and Silicon Image (iScan) chips.

If we want to argue semantics, if and when DVD MPEG decoders deliver progressive scan video directly (I don't think any do today) then the MPEG decoder must have de-interlacing built in for non-film source material.

 

[Sean Moon]

i thought that model JVC television upconverted everything to 1080i anyways? Also, American Beauty has a good ammt of grain in the picture, but was intentional