[mythtv-users] Correctly behaving 576i (or 480i) from vdpau-capable chip?

Paul Gardiner lists at glidos.net
Mon May 24 07:51:57 UTC 2010

Ronald Frazier wrote:
> On Sun, May 23, 2010 at 8:13 AM, Paul Gardiner <lists at glidos.net> wrote:
>> Hi,
>> New TV!!. So I want to build a new front end, mainly to be able
>> to connect via HDMI. For the next year or so, I don't foresee
>> having any HD content to play, so I don't need vdpau, but I'd
>> like to build a vdpau-capable system for future proofing.
>> For now though, with the entirely SD content (PAL 576i), I'd rather let
>> the TV do all the processing (deinterlacing and scaling), and
>> not use vdpau at all. I'm planning on using software decoding,
>> the "2 x Interlaced" software deinterlacer, with X set up to
>> a 576i mode. The TV accepts that mode via HDMI.
>> So what I'd like to know, is whether the vdpau-capable chips
>> can be set up to run that way. I know some chips/drivers
>> don't support interlaced modes. In the past there were problems
>> with nVidia cards and interlaced modes (although possibly
>> only if using XVMC).
> If I'm reading correctly, you want to buy a VDPAU capable card now but
> let the TV do the scaling and deinterlacing anyway. Is there a
> specific reason you want to take that approach? I welcome someone to
> correct me if I'm wrong, but I believe the processing done by the
> VDPAU card beats pretty much everything except (maybe) the highest end
> TVs. Even the cheapest $30 G210 based chip can do Advanced 2X deint on
> an SD stream (and every other deint on HD). I'm not sure what you'd
> gain by ignoring the capabilities of the card you are already going to
> be buying. I'm not aware of any significant VDPAU bugs in mythtv
> either (I haven't encountered any in the last 5 months, and in fact
> the OSD looks much nicer on a VDPAU system)

That's the thing, the TV is pretty high end. It has something called
600Hz intelligent frame creation, which makes motion smoother than
I've ever seen before from a TV. (It also causes the odd artifact
when it gets confused, but over all it's a definite win). That
feature can still be enabled if the frontend does the deinterlacing
and scaling, but I can't be sure without trying it whether that
might look slightly worse than the TV doing it. I have a history
of building frontends, finding they aren't quite as good as other
equipment and then having to build another. I want to avoid that
this time if I can. I do want to try vdpau as well, but I want
to be sure I have the 576i option because that seems pretty certain
to give the best quality the TV can do itself on SD content. If
I then find vdpau is even better then great, but I also have
the case of vdpau being worse covered.

I can nearly get away without a frontend with this TV. It has DLNA
and can play my MythTv recordings directly via ethernet. The big pain
though is for some reason the 600Hz option isn't available when
playing via DLNA. And also it doesn't remember which I've watched
and how far through I am, or let me edit them, or let me set up
recordings - so I think I still need a frontend. :-)


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