[mythtv-users] What does the mythtv-vid branch and OpenGL renderer have to offer

[Steven Adeff]

On 2/7/07, Stroller <linux.luser at myrealbox.com> wrote:
>
> On 8 Feb 2007, at 02:20, Daniel Kristjansson wrote:
> >>>> What is the purpose of the mytht-vid branch??
> >>
> >> Presumably the plan is for this work to be folded back into the main
> >> tree at some point in the future?
>
> Whilst I've got your attention, any comment on this?
>
> I'd hate to get used to the features offered by the mytht-vid branch,
> only to find them removed when I upgrade to 0.21 (or whatever).

Daniel periodically merges head into the -vid branch, so in theory you
could continue using -vid after 0.21 comes out and still get access to
all that 0.21 has to offer.


> >> Is it not possible at present to display "standard def sources at
> >> 1080p in realtime", or are you referring to extra-quality
> >> upscaling &/
> >> or the constraints of your hardware?
> >
> > You can display these quite easily using the XVideo and XvMC
> > playback methods; I've been doing it for about 3 years now.
> > The problem is that the new OpenGL replacement for XVideo has
> > not yet been fully optimized so if you choose to use that
> > video output method you might get some stuttering.
>
> Thanks for your most helpful reply.
>
> > ... One of the the things the mythtv-vid branch gives you
> > is a choice in how to handle different types of video, so
> > you can use a high quality scaler for SDTV, ...
>
> Am I right in thinking the high quality scaler for SDTV will give a
> better picture than just "playing back" an SD source on a HD display?
> I have heard recently of enthusiasts buying "upscaling DVD players"
> which are supposed to give better IQ on a high-def telly than a
> regular DVD player. Is this the difference between the mytht-vid
> branch & regular Myth?

Right now the only scaling is the Xv hardware scaling, which is pretty
poor in terms of whats possible. The move to OpenGL opens the avenue
for better scalers and filters much like the expensive scalers use (or
ffdshow does for windows). This is pretty exciting for those of us
with large HDTV's.

> > ... but skip that
> > HQ scaling step when outputting HDTV since you don't need it.
> > The means that you can get the best quality/performance
> > trade-off for each video type.
>
> I would have thought that skipping the scaling would be "obvious"
> when playing back HD material on an HD display, but perhaps your
> words imply that an additional level of filtering / digital
> processing is applied to SD sources after they've been scaled up? (in
> the mytht-vid branch, I mean?) I guess this would the the way to
> remove or smooth jaggies?
>

Yups. Some in theory may want a high quality scaler to take 1080i
content and lower it to 720p, which would most likely look better with
the proper scaling and filtering than by the TV. This could also help
720p to 1080p scaling for those with 1080p HDTV's, though probably
with less noticeable effect.


-- 
Steve
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