Capture Card Resolution -- was: Re: [mythtv-users] 2 Capture card questions
ken at bizrace.com
Wed Mar 19 18:36:08 UTC 2003
This is great info, but I can't seem to capture above 320x240. I have a WinTV
Go on a P4 1.5G system. I try anything higher than 320x240 the quality gets
worse. It appears to be capturing at 320x240 and scaling up. Do you think
that is what is happening? I would really like some guidance. Is it possible
to force it to not use overlay mode?
Any help would be appreciated.
Quoting Unit3 <unit3 at demoni.ca>:
> Brian Foddy wrote:
> >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...
> I believe that someone had a good idea about deinterlacing which would
> be adequate.
> >Can someone clarify why all the specs state 320x240 for many of
> >these cards and where the confusion comes from?
> I think I can actually answer this! ;)
> When trying to find better software for my TV Wonder under Windows, I
> found some documentation that basically said that if you were using the
> video overlay mode of your video card for display, the card could only
> capture one field of the incoming video, but not both. Essentially,
> limiting the maximum vertical resolution to 240 pixels. The
> documentation suggested that it was easily possible to capture both
> fields if you didn't use overlay mode directly from the card, but
> instead captured both, did some processing, and then output the result
> back to the screen (which is what MythTV, Descalar, and WinDVR all do).
> However, most companies who make these cards would like them to run
> smoother on lower end systems (for purely marketing reasons I'm sure),
> and so their supplied software uses overlay mode for display and is
> limited to 240 vertical pixels. Not suprisingly, most companies then
> also limit their software to capturing 320 horizontal pixels, since
> capturing at 640 or 720x240 would be just silly. :)
> I hope this makes some amount of sense. Also, I don't know if this "can
> only capture one field when using overlay" issue is simple a windows
> driver issue, a WDM issue, or a chipset issue. All I know is that it
> does exist under Windows, as even generic DirectShow capturing software
> will refuse to capture full frames when using video overlay. (I know,
> I've tried)
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