[MPlayer-users] Question on converting to DivX4...

[Rich Felker]

On Sun, Jul 10, 2005 at 08:33:40PM -0700, RC wrote:
> On Sun, 10 Jul 2005 22:24:12 -0400
> Rich Felker <dalias at aerifal.cx> wrote:
> 
> > no it is not. the original content is 'half height'. 
> 
> Yes, yes...  It's half-height, but it's not displayed as such on a TV.
> On an interlaced display, it is properly rebuilt into a full-height
> image.

nope. your eyes rebuild it, not the display. and your eyes will do
exactly the same thing if it's displayed as 60 fields/sec on a
noninterlaced display.

> > interlaced video works like this:
> 
> Blah, blah.  You don't have to explain to me how interlaced video works.

apparently i do since you do NOT get it!

> > no. tfields loses no information, pp=lb loses up to half the
> > information, 
> 
> Okay, I'm listening.  How does pp=lb lose half the information?  It uses
> all the lines in both two fields to generate one frame, so all the
> information is still there.

Compute the number of possible frames, and the number of possible
outputs of pp=lb. You'll find that the latter is vastly smaller.

> It doesn't throw away half the fields and
> interpolate, so I fail to see how you can say it throws away half.
> 
> > tfields throws nothing away. playing back video encoded with tfields
> > to an interlaced display should look identical to watching the
> > original interlaced video...
> 
> You can say it "should" all you want, but I've tried to use tfields
> every different way you can imagine, and it looks terrible.  Not even
> close to a real interlaced signal.  I've tried on a TV-out, on a normal
> CRT, etc.  

Encoding the video first, then playing it at 60 fps with proper
refresh rate, etc.? It looks just like tv to me.

> Objects that should look still, seem rather shaky and unstable.
> In particular, things like the bars across the lower part of the screen
> on cable news channels look absolutely awful with tfields.  The edges
> all around it are obviously flickering, noisy, etc.  Watching the same
> image live on TV, those kinds of things look _rock solid_, and very
> clear.

My guess is that the timing on your computer is very bad.. Maybe bad
ao driver? Does the problem go away with -nosound?

> What an interlaced display does _should_ be identical to what tfields=0
> does (no translation/interpolation)

NO! again you prove that you do not understand interlacing. One field
_really_ is offset by half a scanline from the other.

> in theory, but watch the output of
> that, and the jumping/ flickering is obvious to anyone.

Of course, because you're misaligning the fields!!

> pp=lb doesn't mask all the aliasing, but it sure helps immensely.

no, you just don't know what aliasing is... aliasing is basically
impossible to mask once it's there.

> I appreciate your attempts to help (I don't appreciat being called
> ignorant, but never mind that) but there's hardly any debate.  You
> don't even need very good eyes to see that the output of tfields (even
> on a TV) looks nothing like a normal TV signal.  

again you must be doing something wrong. it looks just like tv signal
on my monitor, and i am a serious videophile who will not tolerate
shitty quality whatsoever..

rich