[mythtv-users] Resolution for PAL analgue TV

Steve Christall mythtv at mctubster.com
Mon Dec 13 09:07:00 UTC 2004

Phill Edwards wrote:

>I'm in Australia so I'm using PAL. I read that the recording dimensions for
>PAL should be 720 wide x 576 high, but when I do this I notice that it uses
>a lot more CPU (20% more) and the picture quality improvement is only
>marginal. Is 720 x 576 right? What do most people set this to on PAL
>systems. Also, I thought I should also set the X "modes" and "metamodes"
>settings  to 720x576 but it doesn't allow this. Am I trying to do something
>stupid here?
Phil.  Is your capture card hardware based encoding or software? 

In my case I have a PVR350 (h/w based) + DVB card.  Both are set to 
record at 720x576 in Myth Setup.

The capture resolution should reflect your source resolution ..... ie 
there is no point capturing at 720x576 if you have a 4:3 analogue 
stream.  640x480 (4:3) is more than enough. 

If you are capturing an analogue output (but digital broadcast) stream 
such as Sky, (Foxtel?) then you want a higher resolution.  Generally 
these broadcasts are widescreen, so you want as much vertical resolution 
as you can get, since most of them are letterboxed anyway.  720x576 only 
gives 5:4 aspect, whereas most shows are 16:9 or movies even worse

My settings are

1 / The DVB card ignores this setting (it doesn't have a choice about 
the resolution, as Myth just saves the mpg2 stream
2004-12-12 20:01:53 DVB#0 Recorder: Card opened successfully.
Videostream: ASPECT: 16:9  Size = 704x576  FRate: 25 fps  BRate: 15.00 
Audiostream: Layer: 1  BRate: 128 kb/s  Freq: 0.0 kHz

2 / More interestingly (for me at least) is that I tried to get an 
display compatible modeline out of my TNT2 card, to drive a 1280x720 
projector.  In the end I gave up and feed it 800x600, which gives me the 
correct aspect ratio.  I assume that Myth on playback is scaling the 
720x576 to 800x600, and then the projector is scaling it to 1280x720 to 
display.  It looks fine, but not for a purist to consider

Hope something helps!

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