[MPlayer-DOCS] [PATCH] DOCS/tech/tearing.txt

[Oded Shimon]

On Thu, Jun 30, 2005 at 11:06:16AM +0200, Diego Biurrun wrote:
> Wow, this patch sure got stuck in the queue for a long time...
> 
> On Tue, Mar 08, 2005 at 12:07:23AM +0100, Diego Biurrun wrote:
> > On Mon, Mar 07, 2005 at 04:44:21PM +0200, Oded Shimon wrote:
> > > What happens with tearing is that halfway through this process, the 
> > > image changes - a very likely event. Because of this, the monitor 
> > > displays the first half the first image, and the next half it shows the 
> > > new image, thinking it's all the same image. The mistake will be 
> > > "corrected" in the very next refresh, as then the entire screen will be 
> > > the new image - too slow. Our eye already caught the mistake. With 
> > > extremely high refresh rates (150hz+), tearing is practically 
> > > unnoticeable.
> > 
> > I'm not particularly fond of this paragraph.  It could be slightly clearer.
> > Sorry for not being more specific right now..
> 
> I must admit I don't get the above paragraph 100%, can somebody
> elaborate?  Rich?

Wow that's old...
Umm, I'll try to explain to you and you try to help me phrase it please - 
It takes 1/60th of a second (or, whatever your refresh rate is) for the 
video card to display a monitor "picture". It does this gradually, from top 
to bottom.
1/60th of a second is a lot of time, enough for our eye to see a defect. 
Half way through this time, MPlayer changes video frames, to the next 
frame. This operation is _immedeate_. The result is, the video card is now 
working on new data, and earlier it worked on old data, and it just thinks 
all of this is the same, and continues showing it. you end up with the top 
half of the monitor being frame 1, and the bottom being with frame 2.

11111111111111 } "painting" all of this on 
11111111111111 } the montior is a 1/60th second process
11111111111111 } ...
11111111111111 }
11111111111111 }
11111111111111 }
11111111111111 }

11111111111111
11111111111111
11111111111111 } oops, halfway through, MPlayer changed the picture!
22222222222222
22222222222222
22222222222222
22222222222222

22222222222222
22222222222222
22222222222222
22222222222222
22222222222222
22222222222222
22222222222222

I hope that's clear enough...

- ods15