[mythtv-users] Objective IVTV quality measurement instructions

dean vanden heuvel deanv at cox.net
Sat Aug 14 23:10:39 EDT 2004


I myself have been experimenting with capture on the PVR-250.  I can't decide with my eyes alone using normal content whether or not I gain anything by capturing 720x480 as opposed to 640x480 or even less.  It takes too many keystrokes in Myth to go from one to the other, and by the time I display the alternate, I can't really say for sure if the higher resolution is better.  I do receive (and capture) HD content that is broadcast @ 1280x720, but because I have only the S-video input for my PVR-250, I must use the S-video out from my satellite receiver, and thus some of that resolution is lost.

So, would your experience tell you that I can get replay that is *just as good* if I capture at 640 (or less), or should I stay with 720?  for live TV, storage does not matter, but for recorded content, using the lower resolution and a lower bit rate could save space.  Alternatively, using the lower resolution for capture and keeping the same bit rate, resulting in roughly equivalent storage requirement, MAY result in a BETTER picture, If I understand this correctly.

What would your experience tend to recommend?

-dvh

On Fri, 13 Aug 2004 09:50:43 -0400 (EDT)
Cory Papenfuss <papenfuss at juneau.me.vt.edu> wrote:

>  	I posted this awhile back, but I never got too many responses.  My 
> PVR-250 OEM has what I consider to be only adequate capture resolution.  The TV 
> it's connected to can do a better job of displaying cable TV signal and 
> produces cleaner results.  I've reduced the variables enough to know it's 
> not my tvout on the mythtv box.  Playing test patterns in a DVD player 
> recording it with mythtv can help find this out.  I mastered a burnable DVD 
> image awhile back:
> 
> http://www.ee.vt.edu/~mythtv/TEST.tar.bz2
> 
>  	The EIA1956 test pattern is on there, at 720x480.  Since it's limited 
> to 720 pixels, the test pattern itself is only 720*3/4=540 "lines of 
> resolution" on a 4:3 TV.  My pvr250 can only resolve about 400-450 lines, even 
> when capturing via the svid direct from the DVD at 720x480.  The TV OTOH can 
> resolve the full 540 lines when connected directly to the DVD player.
> 
>  	Anyone who feels like testing this and reporting back would be 
> appreciated.  I discovered just how crappy my low-end BTTV card was (350-400 
> max)... took it out of the box after that.
> 
> -Cory
> 
> 
> *************************************************************************
> * Cory Papenfuss							*
> * Electrical Engineering Ph.D. Graduate Student                         *
> * Virginia Polytechnic Institute and State University 			*
> *************************************************************************
> 
> 


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