Poor Quality DVDs
 

Perhaps "poor" is too strong a word. I actually think that "not quite perfect" would be better, but then no-one would read the post.
I have Xine for playing DVDs on Linux. When they play, there's no lag or anything, but during times when things move quickly, it's just about discernible that instead of solid objects moving quickly, I am getting interlacing (I think that's the word - it means lots of little lines all mashed up together right?) . This is most obvious in my favourite DVDs - Futurama, due to the fact that it's mostly solid blocks of colour.
To illustrate a little better, using ASCII:

Instead of this three stage process:

------------++ -------+++++++ --++++++++++++
------------++ -------+++++++ --++++++++++++
------------++ -------+++++++ --++++++++++++
------------++ -------+++++++ --++++++++++++
------------++ -------+++++++ --++++++++++++
------------++ -------+++++++ --++++++++++++
------------++ -------+++++++ --++++++++++++
------------++ -------+++++++ --++++++++++++

I might get something like this:

------------++ ----++++++++++ --++++++++++++
------------++ ----------++++ --++++++++++++
------------++ ----++++++++++ --++++++++++++
------------++ ----------++++ --++++++++++++
------------++ ----++++++++++ --++++++++++++
------------++ ----------++++ --++++++++++++
------------++ ----++++++++++ --++++++++++++
------------++ ----------++++ --++++++++++++

Or maybe even this:

------------++ ------------++ --++++++++++++
------------++ --++++++++++++ --++++++++++++
------------++ ------------++ --++++++++++++
------------++ --++++++++++++ --++++++++++++
------------++ ------------++ --++++++++++++
------------++ --++++++++++++ --++++++++++++
------------++ ------------++ --++++++++++++
------------++ --++++++++++++ --++++++++++++


Obviously, there's only so much you can do with ASCII, but hopefully you get the idea.
Anyway, so my question is:
Is this anything fixable? Is it to do with DVD decryption not being perfect? My libdvdcss, libdvdread and libdvdnav are all pretty recent (very recent in fact - can't remember the version but they're less than a month old). Is it Xine? Am I just being over-sensitive? - my girlfriend can't tell, but she's not a vision perfectionist.
Thanks in advance
Guy

that's a good post describing your problem. :)
but have you tried mplayer? you can download it from http://mplayerhq.hu.

do you get the same effect if you play the DVD in a regular DVD player?

You don't mention what kind of machine you have so I cannot comment on whether it might be underpowered or not.

My laptop's a PII333 with 192 Megs of ram. Out of the box, DVDs are unwatchable, even though when I had win98 and powerDVD I could watch them flawlessly.

The things that saved me were 1) tweaking the machine to make sure I get the best performance I can get (ie: recompiling the kernel, turning on DMA for the DVD drives, things like that), 2) switching to Mplayer and 3) (most important) compiled Mplayer from source.

Even compiling from source I could never get DVDs to run in Xine...mplayer however handles them so well that I find the quality is even better than in Windows...the only thing I miss is having the DVD menus and such, which I never got to work.

I've been thinking about using MPlayer for a while now. I might give it a go. My machine is almost certainly not underpowered (2GHz with 1GB of RAM) and it plays fine in normal DVD players and also on Windows. My system is built from scratch (http://www.linuxfromscratch.org - highly recommended) so there shouldn't be anything stopping it. Have you installed libdvdnav? That will help with DVD menus
Guy

No that's certainly not underpowered. I find that strange tho...
I mean I have an athlon 1ghz also...and that plays DVDs just fine using Xine.

I won't say DON'T try mplayer...its great...I'm just saying that the problem probably lies elsewhere.

Do you have DMA enabled on your DVD drive?

Yes, I have DMA enabled. Personally I think the problem lies with libdvdcss not being perfect, but if no-one else has had this problem...

is there any specific reason you think libdvdcss is the problem?

Xine works fine for other formats (avi, mpeg, rm is all I've tried). Also, I know that libdvdcss is not the "true" way of decoding DVDs and has to "sort of crack the encryption". The other reason I think this is because when I have used transcode to rip dvds in the past, it had the same problem.
Guy

Bump!
Also, I have tried MPlayer to no avail - the exact same problem occurs. I have tried different output plugins on both, and the ones that work at all all work the same, i.e. not very well (if that makes sense)
Firstly, had ANYONE else had this problem.
Secondly, does anyone use an onboard SiS graphics card with Thomas Winischhofer's drivers (and DRI enabled)? Do you have this problem?
Thanks
Guy

Well, one thing to try, start it as root, with
nice --20 Xine
(note TWO minus signs)

If that fixes the problem, or makes it less noticeable, then it is a horsepower problem. My guess would be that it is the video driver. While windows has optimized drivers for your onboard SIS card, you are using the reverse engineered driver that simply takes too much CPU.

R.O.

Guygriffiths, all you need to do to solve your problem is to press the "i" key when you're watching your DVD. That will turn Xine's deinterlacing mode on. Press "i" again if you want to turn deinterlacing off. Xine's default deinterlacing algorithm drops one field (and half your video quality) but you can choose other algorithms from Xine's menus.

I've posted a somewhat more detailed reply to the following thread:
Non-interlaced DVD playback? No encryption-probs? Is this possible?

This problem has nothing, and I repeat, NOTHING to do with your computer's performance.

I don't even have a DVD player but that effect seems to me the so called "tearing", which happens when the graphics card starts sending pixels to the screen but it's not coordinated with the screen.

anyway, check for option like "vertical sync" and activate them, look in your video drivers and such.
I think there are also some issues with double buffering and activating vertical sync.

Not a very useful post, but at least now you have one name for the problem :D

Good luck

No offence, Hiper, but you're not correct. Here's the deal.

NTSC countries have 60Hz power, alternating current. NTSC signals, therefore, are composed of two sets of horizontal lines, called fields. One field shows every even line of the image; the other shows every odd line of the image. How often do we switch between fields? 60 times per second. Televisions look smooth and uniform because their images take time to fade, and one field therefore remains onscreen when the TV switches to the next. Watch an NTSC signal on a computer monitor, however, and it's normal to see where the fields are.

PAL countries have 50Hz power. The numbers are different but the same principals apply.

There are various "deinterlacing" algorithms that will show an interlaced signal on a progressive monitor without showing these artifacts. In Xine, you turn them on by pressing "i". Using MPlayer? Specify one on the command-line ("mplayer -vf help").

dugan: Thank-you. You are spot on with this. I wonder why it's not enabled by default, and why I've never seen it mentioned before.