[vdr] Re: choosing a FF card

[Ian Molton <spyro@f2s.com>]

Tony Houghton wrote:

> Too large for what? ICBW, but my understanding is that if a device is
> outputting 576 lines in PAL, the height is fixed by the TV and can't be
> controlled by the device, except that it can probably be shifted up and
> down a bit. Then the device has to fill the horizontal field, including
> overscan, to make sure the aspect ratio is correct.
The overscan is the part of the picture thats displayed offscreen such 
that blooming and other distoprtions present in the garbage TV tubes we 
have dont encroach so visibly on the picture.

The amount of overscan is determined by the timings of the video mode 
you present to the TV, not the number of pixels per row or number of 
lines. with analogue TVs (or monitors) there isnt any defined 1:! 
mapping of pixels on screen to pixels in the framebuffer and its not 
uncommon for poorly adjusted TVs and monitors to have half pixel 
overlaps or worse between pixels, etc.

> If a graphics card is showing an 800x600 desktop on a TV with no
> overscan, then it's probably scaling to fewer than 576 lines. If you're
> only concerned with video, then I think you'll find the amount of
> overscan is the same as you'd get from a DVD player or STB.
Im displaying a pal res output, 576 lines. but the amount of overscan in 
the timings produced by my board is both too great and unadjustable.

> > 3) Is the TV output properly interlaced? what about when playing a DVD 
> > which is progressive-scan (most movies) ?
>
> I don't know about FF cards, but my DXR3 handled both extremely well,
> although I had to use it in NTSC mode for NTSC DVDs. AFAIK FF cards are
> better than the DXR3 in terms of scaling non-standard sizes and
> displaying an OSD.
So how does the card do the re-interlacing for progressive scanned 
material? (do they all use some standard algorithm?)

> > basically, I want really really good TV output from both DVB and DVD, 
> > possibly divx (how does that work on these cards?) too.
> DivX has to be converted to MPEG1 on the fly. You've got an EPIA system
> haven't you? You might well not have enough CPU power. And what's wrong
> with the CLE266?
well the epia decoder works very well. what doesnt work so well is the 
chrontel tv encoder in the thing which gives a low quality, noisy, 
non-frame-parity-aware output. if only my TV had RGB progressive input...

> Also, I don't think there's such a thing as a DVB-T FF card,
Some people seem to have them...