Capture Card Resolution -- was: Re: [mythtv-users] 2 Capture card questions

Ray Olszewski ray at comarre.com
Wed Mar 19 06:24:20 UTC 2003


My understanding too is that cards like the WinTV series can capture up to 
720x384 or thereabouts (whatever the full PAL resolution is, a bit higher 
than the full NTSC 640x480); I'd certainly believe 720x480 is possible, 
though I can't vouch for it.

I don't know what you've seen that you think are "all the specs", for the 
WinTV cards, so I can't "clarify" what they say. The spec sheet produced by 
Hauppauge for the WInTV Go card, for example, does not list a maximum 
resolution. Perhaps if you would provide some references to what you are 
reading, I or someone else here can assist.

The 320x240 (for NTSC) limit is often a practical one, set by the CPU's 
processing speed and hard disk transfer rate. (And the fact that actual 
NTSC signals consist of 59.94 fps, composed of interlaced pairs of 320x240 
images.) As CPUs get better, buffer memory more plentiful, and hard disks 
and controllers themselves faster, that limit becomes less binding, and the 
equipment used in a typical MythTV setup (as I infer from reading this 
list; I use wimpier hardware myself) should not be subject to this 
constraint. This *may* be the source of what you refer to as the 
"confusion" about resolution capabilities.

At 11:18 PM 3/18/2003 -0600, Brian Foddy wrote:
>On Monday 17 March 2003 01:02 pm, Bruce Markey wrote:
> > Unit3 wrote:
> > > Brian Foddy wrote:
> > >> 2nd question...
> > >> There are several specs I've seen that the same WinTV series
> > >> only has capture resolution of 320x240.  I can't say I know
> > >> for a fact if this is correct in Linux or not.  Does anyone know
> > >> for sure.  I know I can set myth higher, but is the card really
> > >> giving the higher resolution?
> > >
> > > I was under the impression that *all* bt878 cards could capture at
> > > 720x480, given a proper set of drivers.
> >
> > AFAIK that is correct.
> >
> > > I'd say pump the res up in MythTV and see if the quality increases or
> > > not.. it should be evident right away if you're getting 4x the
> > > resolution or if it's just scaling up 320x240.
> >
> > http://www.mythtv.org/docs/mythtv-HOWTO-19.html#ss19.4
> >
> > In Setup->Playback, turn off Fixed Aspect Ratio then during
> > playback, press "f". The picture will be in a window the size
> > of the original recording dimensions.
> >
>
>Thanks for the reply, but I don't think your proof is valid.  I'm sure
>the Myth will replay whatever resolution it thinks its capturing, but
>that says nothing to what the card is delivering...
>
>Can someone clarify why all the specs state 320x240 for many of
>these cards and where the confusion comes from?






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