Problem with persistent scaling/shifting in RADEONDisplayVideo()

Roland Scheidegger sroland at
Wed Jul 30 07:17:10 PDT 2008

On 29.07.2008 20:43, Thomas Hilber wrote:
> On Tue, Jul 29, 2008 at 02:23:09PM +0200, Roland Scheidegger wrote:
>> That's true but last I heard CRT TVs are a dying breed.
> who cares:)
>> Ok, I see your point. But if your output device is a projector, LCD (not
>> sure about plasma right now) at some stage deinterlace just has to
>> happen somewhere anyway (and the quality of this in a cheap output
>> device might be questionable too). Too bad with HDTV you still have to
> right. but from my experience recent dedicated hardware deinterlacers
> mostly produce better results than their software (PC based) competitors.
>> care about deinterlace since 1080i is very common (even though there are
>> very few, if any, output devices which would support native interlaced
>> display for this mode).
> right. The original purpose of my patch was to establish a basis to
> synchronize VGA video timing with an external signal source (e.g. a DVB 
> stream). Otherwise you always will have more or less jerky playback.
> The capability to produce fully synchronized interlaced RGB output on a VGA
> port is only a pleasant by-product of this.

Actually, this is a very interesting patch. I've been thinking about
this a bit lately. How much jerkyness do you actually get when it's not
synchronized? I'd assume that if you use an output mode which is as
close as possible to the supposed 50i PAL timings, you should only get
non-smooth motion (that is a frame displayed twice or skipped) very rarely?
And, a problem you'd have with htpc would be that you often have
different source material - probably 25p, 50i, 23.976p, 24.0p,...
So, even in a setup where you wouldn't care about (output) interlace and
are just fine using a scaler (for different source resolutions), you'd
still need to switch output modes to match (or use an exact multiple) of
the framerate, which then could be synchronized with your (or similar)
patch. That's an awful lot of hacks to get most smooth playback without
any API really to make it work in some sane way...


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