[mythtv-users] Having problems / Need info on BOB Deinterlacing

[Mark Kendall]

On 5/31/06, James Buckley <james at logicland.co.uk> wrote:
>
> Hello, I've been building my Myth box for well over 3 moths now;
> everything
> works except for one major problem, TV playback (lol).
>
> I find that TV playback with either no deinterlacing or non BOB
> deinterlacing just doesn't have enough frames a second to be watchable.
> For
> example, if you compare news tickers you get on sky news or BBC news, over
> normal Freeview / DVB-T, they are much smoother than through MythTV.
> Unless
> I can get the tickers to be as smooth as normal TV (or very close to), I'm
> gonna end up scrapping this project, something I really don't want to do.
>
> My setup is as follows, I have a Myth box running latest SVN build,
> outputting over DVI (from a Nvidia 6200 chipset) direct to my LCD TV. I
> haven't created a custom modeline, as I can get crisp, no overscanning
> output, using the resolution 1360x768, progressive. Now, the solution to a
> low frame rate is to use BOB deinterlacing, this makes TV smooth, but has
> some very horrible side effects.


James

Is this live tv? if so, you should be aware that there is an issue with live
tv in svn that has resurfaced - probably dvb related. Playback is all over
the place until you pause and unpause - very noticeable for me and proving
nigh on impossible to track down.

That aside, I've been working to get the same 'perfect' output for some
time. My solution was feeding my lcd tv 720x576i over the DVI connection
(Samsung LE32xxx). With BOB deinterlacing enabled the tv syncs with the
incoming feed and performs all the de-interlacing and image enhancement
itself. Result - picture quality almost indistinguishable from the tv's own
dvb tuner. Tickers, panning, sport - all perfectly smooth. I still get a
slight 'bobbing' but barely noticeable unless you're really looking for it.
Even better, the tv seems to do some buffering of its own internally and
smooths out the smaller glitches in playback.

If you can get that up and running, the downsides are:-
 - interactive tv and osd display is lower quality due to the way the osd is
rendered onto a 'half' frame (unavoidable with bob)
 - gui runs at 720x576 (and is stretched - gui cannot handle non-square
pixels). You can use xrandr to avoid running the gui in this mode, but there
are issues with xrandr and aspect ratio at the moment.
 - you will get overscan but you get used to it quickly enough -
interactive, for example, actually expects some overscan.

Once HD is fully functional, I'll start using xrandr to switch between
1080i, 576i etc but at the moment I'm happy with 576i. (and be aware - I
have an FX6200 as well - there is a bug (bugs!?) in the latest nvidia
drivers that prevent 1080i playback using xv/xvmc with certain settings.
Cost me a large chunk of last weekend to find that out...)

Regards

Mark
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mythtv.org/pipermail/mythtv-users/attachments/20060531/f9611609/attachment.htm