[mythtv-users] Video Scaling questions

Peter Lee petel at cs.cmu.edu
Wed Dec 10 12:01:32 EST 2003


This leads me to another question: How feasible would it be to implement a
"justification" mode?  What I mean by this: I have a Panasonic 16x9 plasma
display.  Two nice features of this display are (1) it has a VGA input and
(2) it has a "justification" mode for stretching 4:3 signals to 16:9.  What
this mode does is leaves the middle 50% of the image untouched, but
stretches out the left and right 25% to fill the widescreen display.
(Actually, the stretching has more of a gradient, but you get the idea.)

This justification mode works remarkably well.  For most 4:3 programs, most
people don't notice that any stretching is going on at all.  I think this
happens because most of the "action" is in the middle of the image, not at
the left and right edges.

Now, for my question/problem: The plasma display provides justification mode
for component video and s-video inputs, but *not* for vga inputs!  By
connecting my MythTV box directly to the VGA input of my plasma display, I
get really sharp, clear images, which I use for watching dvds.  (I think I
have the display set to something like a 1280x800 or something like that, I
can't quite remember now).  But since I really like the justification mode,
I am watching TV and other 4:3 recordings via s-video.

So, my question (finally): What would be involved in implementing the
justification mode in MythTV?  With the increasing number of widescreen
displays, many of which don't provide justification mode, I think this might
be a nice feature.  Unfortunately, I'm not anywhere near capable enough to
contemplate implementing it myself (and I think it might be hard for anyone,
actually), and furthermore I'm not 100% sure that it is a good idea overall.

Comments?

Peter
 

On 10 Dec 2003 01:26:21, Brian Foddy wrote:
> 
> On Sunday 07 December 2003 08:14 am, Doug Larrick wrote:
>> On 12/06/03 23:56:33, Brian Foddy wrote:
>>> Is there a difference in doing this [DisplaySize in XF86Config], vs
>>> changing the aspect ratio in the card profile?
>> 
>> Well, the help text for the card's aspect ratio says "Sets the aspect
>> ratio of stream generated by your PVR," i.e. the aspect ratio of your
>> recordings.  XF86Config sets the aspect ratio of your output display
>> device.  Both of these need to be correct for the right thing to happen
>> automatically.
>> 
>> -Doug
> 
> A couple final comments on this thead.
> I tried re-setting the capture card ratio back to
> 4:3, and setting the DisplaySize to 1280x720, but I couldn't
> get Myth to default to a 16:9 display.
> 
> However, as I was playing around, I'm leaving it for
> now.  Somehow, and I'm really at a loss to explain,
> capturing a standard ntsc show using either a pvr or bttv
> card, displaying on a 16:9 hdtv using a component converter
> set to 1280x720p, and using the myth scaling set
> to 16x9, the whole screen is properly filled (which I expected),
> but the aspects are much closer to proper.  Not the
> standard 16x9 stretch I'm used to seeing when I
> use the TVs 16x9 scaling of live TV.  I can't explain???
> Not sure how you did it, but I like it...  The only thing
> I can think of is the normal TV overscans a bit, and I
> tweaked the 1280 numbers so the horizontal overscan is a minimum,
> thereby making the aspect ratios much closer to proper.
> 
> Brian



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