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

Andre mythtv-list at dinkum.org.uk
Thu May 27 10:33:35 UTC 2010

On 27 May 2010, at 11:05, Paul Gardiner wrote:

> Jean-Yves Avenard wrote:
>> Hi
>> On 24 May 2010 17:51, Paul Gardiner <lists at glidos.net> wrote:
>>> 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
>> is that the LG one? they are the only ones who dare to use the word
>> 600Hz TV AFAIK...
>> I would still use the Advanced 2X vdpau deinterlacers and see how it
>> looks for you.. I'm sure you will be surprised.
> Tried it now, and it's not as good. But I don't think this is because
> of vdpau doing any worse a job of deinterlacing than the TV. I think
> it's a UK specific problem. As I've mentioned before, our SD TV here,
> although it is supposed to be 50i, is effectively 25p because each

It does vary depending on content but 50i is rare on SD channels, they are so short of bandwidth that dropping almost everything to 25p helps a great deal! That's why everyone complains so much about the football it's often the only thing that's not 25p!

BBC HD did a little experiment recently with the Only Fools & Horses prequel drama "Rock & Chips" this was broadcast as 25p on BBC1 and 50i on BBC HD, (ok for the pedants 576i25psf and 1080i25) read the BBC blogs for the in depth discussion but the consensus was that this was one of the best broadcasts in some years for technical quality and realistic motion.

vdpau advanced 2x does correctly de-interlace to 50p from 50i any of the 2x de-ints should, there just isn't that much interlaced material broadcast. If you pause and single step though a seconds worth of video you will either see 25 different images or 50 depending on i or psf, usually a few frames will show it up, if you need two frame steps to see a change.

> frame's pair of fields aren't time separated. That's not universally
> true, but the majority of transmissions are like that. So playing
> that through a unit that does the deinterlacing is, I imagine,
> producing pairs of identical frames, and then the TV's IFG cannot
> do anything useful with it. Whereas if the original 576i is sent
> to the TV, although it's still got the non-time-separated fields,
> the TV can still work out what to do with it.
> Also I imagine my whole liking of IFG is down to having crappy
> UK 25p as the alternative. If our transmissions were true 50i
> I'd probably prefer IFG turned off.

You are going to love 1080p50, such a shame that Ofcom vetoed it's last minute inclusion in the Freeview HD spec, it will be at least another 10 years before we see any broadcast in the UK.

I have a recording of a Baseball game shot natively at 720p60 and although I can't stand Baseball it's great to watch due to the smooth motion. IMPO all broadcast HD should be 720p50/60 leave 1080p to bluray and 1080i should be shot at dawn, I have a 90" projector screen and would rather watch 720p50 than 1080i25, really you can't properly see the difference <50".

> Anyway, I haven't managed to try 576i via HDMI yet. I haven't
> found a way via minimyth's config to get the correct X set up.
> I did manage 1920x1080p60, which strangely didn't look that bad,
> although it really should have done given that all my content is
> 50Hz or 25Hz. I don't understand that.
> Cheers,
> 	Paul.
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