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

Edward Wildgoose Edward.Wildgoose at FRMHedge.com
Thu Mar 20 11:24:41 EST 2003

> Edward Wildgoose wrote:
> ...
> > They may be able to capture higher, but as of myth 0.8, myth
> > can't capture 720x576 for PAL full resolution.  (Or in fact
> > 780x576 as stated in some docs?)
> >
> > It seems that the "height" box (in setup screen) is limited
>  > to a max of 480 only.  I assume that if I dig into the DB and
> > change the setting manually, myth will record at the higher
> > resolution ok? (obviously subject to CPU..)
> Bummer. I'm surprised none of the PAL users mentioned this
> before 0.8.

> Matt is right. The code exists and this used to work. However,
> the check to see if you use PAL or NTSC got lost in the shuffle.
> I don't have PAL either but I changed my settings and verified
> that it now allows 768x576 for PAL and a max of 720x480 for NTSC.
> If you, or anyone with PAL could volunteer to help, please update
> to the current CVS and test recording at 768x576 (or 768x288 to
> save CPU cycles). In looking at the bt878 specs (as opposed to
> vague recollections ;-), the chip should allow PAL widths up
> to 768. However, there is at least one reference to 720x576 in
> libavcodec so I'm not sure recording will work at this width
> even if it is supported by the chip.
> Please report the maximum width that does work so that we
> don't suggest a width on the setup page that would fail.
> If no one responds, I'll set it back to 720.

Yes, I will update from CVS tonight and retest (I am on UK time).  Will post an answer tomorrow.

I can record at that resolution using lavrec for what it is worth, so it definitely is a real mode (although I don't know whether I am really recording that much detail of course).  And it also meets the definition of 4:3 ratio, so perhaps this is why.

Any chance of pointing me at the spot of code that you changed?  I would like to add a set of eyes to the code, but so far I have found it slightly difficult to find the "meat".  Is there an overview document anywhere?  (Perhaps embeded in a source file, etc?).  In particular it would be useful to get a pointer to the relevant chunk of encoding code where I could add some debugging to check for "quality", ie framedrops, etc.  This would be useful for tuning settings for maximum performance.

Excellent product.  Thanks folks


More information about the mythtv-dev mailing list