[mythtv] Re: [mythtv-commits] mythtv commit: r7463 by danielk (ie using 16:10 display)

[Glen Dragon]

Quoting Daniel Kristjansson <danielk at cuymedia.net>:

> On Thu, 2005-10-13 at 13:17 -0400, Glen Dragon wrote:
>
>> have been unable to use the full resolution of the screen. I am forced
>> to cut down the myth display size, othewise I get bad 1080i interlacing
>> tearing.
> You need to enable deinterlacing to prevent the tearing.

I actually do have it on (kernel i think), tho off/any mode doesn't 
make any difference.  I've described this problem to the list several 
months ago, and a couple of poeple helped me to  sort of figure it out. 
  The only way I've been able to make it go away is if i use an odd 
myth resolution, ie 1624x1010, so it doens't fully fill the screen. If 
I have the myth resolution fill X's resolution, then I get really ugly 
tearing, not just the normal interlacing tearing that I'm used to.


>> Does this commit help me?  I currently don't use Xinerama (to my
>> knowledge), since I only have a single screen in X.  X is configured
>> for the 16:10 resolution (1680x1050).  What options should I change to
>> enable this feature?  I looked quick, and I didn't see it on the GUI,
>> tho I might have missed it.
> You didn't miss it. It is only enabled when you are using Xinerama.
> When you don't have Xinerama, MythTV can detect the aspect ratio.

Okay, so this change, while nice, doesn't sound like it does me any 
good. Oh well.

>
> The problem you are having has nothing to do with the aspect ratio,
> the problem is that to fit a 1920x1080 video onto a 1680x1050 display
> you need to resize the frame, or cut off part of the video. In your
> case you are resizing the 1080 lines to something like 945 lines.
> This is done in hardware when you use XVideo. Your hardware uses
> point sampling without knowledge of the interlacing, giving you
> both spatial and temporal aliasing (better sampling would cost more).
> If you turn on deinterlacing in MythTV you will remove the temporal
> aliasing, which causes low frequency waves in the output.

This makes sense, although turning on myth's deinterlacer seems to make 
no change to to my ugly problem (the low freq waves?).  See my comments 
above & below.

>
> MythTV could have another letter-boxing mode which chops off the
> top 15 and bottom 15 lines and some portion of the left and right
> of the video to fit exactly onto 1050 lines of a 16:10 display.
> This would eliminate annoying low frequency waves, but you would
> still get the less annoying high frequency waves if you didn't
> use deinterlacing. However, these high frequency waves can be
> eliminated with hardware deinterlacer/"line doubler" hardware.

The alternate letterboxing (16:10) feature sounds like it has potential.

Your last sentence confuses me, Does the sw de-interlacer prevent low 
or high frequency waves? Your two paragraphs seem to contradict 
themselves, or maybe I just misunderstood.

Unfornately my display is only a LCD monitor, (Dell 2005fpw) and 
doesn't have the tv hardware (hw deint/line doubler/etc).

-----------------------------------------
Glen Dragon
Lead Firmware Engineer
Harris RF Communications