Richard Rauch said:
> No, I don't think so.  The color variation between what mplayer produces is
> visually substantialy higher (more than rounding/truncating to 12 bits can
> explain).  However, such truncation may explain the slightly less smooth
> effect of mplayer.  (On the other hand, 12bpp *is* fairly capable,
> especially if you don't have 20/20 vision and don't press your nose to the
> monitor...(^&)

Could be - absolutely... posterization, however, is one possible cause.

> My present theory is that Ogle is doing some kind of simplistic color
> correction that washes out the low end---or isn't doing any color
> correction at all, while mplayer either isn't doing correction (thus
> leaving "black" as "black"), or is doing more intelligent correction.

Yes, this could be too.  If they have different decoders, they could be doing
very different things.
[snip]

> Remember that 4 bits per channel != 4 levels, and 12bpp != 12 colors.
>
> Calling 12bpp "severely posterized", I think, is a bit extreme.  (^&

Not at all.  I use my pc as a DVD player to feed a projector which hits a
screen about 6 ft wide.  At this size, the difference from 30bpp to 24bpp is
apparant.  When viewing on a 19" monitor which has been calibrated, the
difference from 24bpp to 16bpp is very apparant.  Trust me, if you see a well
setup DVD player on a PC, many things become apparant - the exactness of the
PC unmasks many faults of the system.
Again, I'm picky.  But these are realworld "issues" - it's not a blue stripe
around the outside of a CD...
If 12bpp works for you, then go for it.  4 bits/channel = 16 distinct
shades/channel (of course, this assumes an even color distribution, which is
reasonable but not always realworld).  Trust me, seeing 16 shades of green
trying to represent a big, green field just doesn't work.  It looks like a
1970's psychedelic poster.
> I suspect you've not actually used it, or do not appreciate how
> significant the variation between mplayer and ogle is---or overestimate the
> difference between 12bpp and 16bpp (or even 12bpp and 24bpp).  If
> represented in 12bpp, Ogle's "black" would be about 222 on my system, I
> think.  mplayer's black is black (000).

Again, I've used ogle [albeit briefly, say for 45 minutes] on my 6 ft wide
front projection screen.  It's definitely got room for improvement, but it's
not _bad_.  I have not used mplayer - I can't comment there.
> If the server is running in 24bpp, there are artifacts (most visible when
> the image changes rapidly, as when a beam of light moves rapidly over an
> object).  This causes visible tearing.  At 16bpp, the images don't degrade
> (since they are 12bpp anyway) and the tearing goes away, being replaced by
> smoother animation.

That's a possible effect of posterization (not enough color space to
accurately display detail).  It could also be inadiquate bandwidth to the card
(24bpp == more data == more dropped frames == artifacts).  If you want to
avoid the tearing and combing, then you have to deinterlace the image.  Most
DVDs these days are encoded as interlaced sources.  Modern DVD decoders for
the PC will do 3/2 pulldown reconstruction and conversion to a progressive
frame rate to avoid combing, tearing and jutter.  The DVD playback software I
use (on an M$ platform) does a relatively good job of this.  ogle does not do
any of it (yet - that's something I'm hoping to help change when I have more
copious spare time).
[snip]

> I'm not sure what constitutes "getting serious".  A movie *is*
> entertainment, after all.  (^&  (And I don't plan on charging admission to
> let people watch movies on my computer.)  However, I'm satisfied enough
> that I'll probably buy a movie from time to time.

Well, that's fine for you.  Many people will argue that music is entertainment
as well, yet there are people out there willing to spend tens of thousands of
dollars on good loudspeakers, amps, etc...  Same thing for wines, cars and
computers...
Again, as long as you enjoy it, that's what's most important.

But there are well known facts, problems and solutions of DVD playback that
are real and have been researched to a great extent by fanatics like myself. 
Posterization is real.  Tearing and combing are quite real.  Video signal
bandwidth issues are quite real, in almost any form.
> But how much is actually coming out of your card?  If your card claims to
> be a 32bpp card, realize that 32bpp usually means 8bpp are taken up by an
> alpha channel.  If your card is "really" only doing 24bpp of actual color
> output, then those extra 2 bits per channel per pixel are just going to
> help with antialiasing.  (Not a bad idea, but not fundamentally impossible
> with a software decoder, either.  (^&)

Nope, 30bpp is actually coming out.  IIRC there is no alpha channel for the
overlay.  Overlay isn't even visible in the framebuffer - it's "merged" onto
the output signal as the video signal is produced.  Try using an M$ box for
playback sometime, and try taking a screen snapshot.  The whole screen will
come out, except for the DVD image.  It's not due to copywrite protection
(although I'm sure M$ thinks it's a great side effect) - it's due to the
overlay not even existing in the framebuffer.
>> difference.  But, then again, I'm picky about my video.
>
> Heh.  Most are, I think.  The question is the relative weight that <X>
> enjoys versus <Y>.  I'm a grad student with very low income at the moment,
> so a $400 or $500 video card just on which to watch a handful of movies is
> a huge waste.  A $40 or $60 card that I'll "have" to replace in time with a
> "real" card for DRI support is also a waste.  A $100 or $150 card when DRI
> is available is almost defensible, though, so I'm waiting...the longer I
> wait, the more leverage I get for that $100 or so.

Absolutely.  But realize that if you're going to be bothered by some of what
you've seen, it will either be solved by 1) hacking some good filter code into
ogle/mplayer and/or 2) upgrading to an AGP card.
> As am I.  (^&

Good to hear!  Now, if you want my opinions on some good movies...

[just kidding ;-]

Enjoy the movies!

P.S. if you're ever around NYC and want to see some of what I've been
soapboxing about, do get in touch.  We'll grab a beer and see some movies. 
Maybe we can get some of the other netbsd-nyc people over for a good film.
-- 
-Jon
 "As three unwavering bands of light, we were simple and separate and
 beautiful.  As machines, we were flabby bags of ancient plumbing and
 wiring, of rusty hinges and feeble springs.  And our
 interrelationships were Byzantine."
 - Kurt Vonnegut, Breakfast of Champions