Problem with persistent scaling/shifting in RADEONDisplayVideo()

Roland Scheidegger sroland at
Tue Jul 29 05:23:09 PDT 2008

On 29.07.2008 13:25, Thomas Hilber wrote:
> On Tue, Jul 29, 2008 at 08:11:21AM +0200, Michel Dänzer wrote:
>> On Tue, 2008-07-29 at 01:43 +0200, Roland Scheidegger wrote:
>>> "high quality" and "RGB/PAL" doesn't really fit in the same sentence if
>>> you ask me...
>> Probably nothing beats a good TV when it comes to de-interlacing etc.,
>> so it makes sense to preserve the broadcast signal as much as possible.
>> I assume that's what 'high quality' refers to in this context.
> that's exactly what I wanted to say. Of course our solution can't be
> better than RGB-SCART itself. 
> But until now almost all VGA-based softdecoder solutions had to 
> deinterlace in software.
> What makes not much sense if right after this the VGA CRT controller 
> re-interlaces the frame again. By doing so considerable CPU power is 
> wasted for getting even worse picture quality.
That's true but last I heard CRT TVs are a dying breed.

> As mentioned above here are some further explanations:
> With my patch we can grab the untouched fields right after the software
> decoder and route them straight through to the VGA port. 
>>From there you ideally display the fields on a native-interlace-capable
> device like a CRT. 
> I've heard that more recent LCD displays also produce attractive picture 
> quality on SCART input. Though at the expense of huge amount of signal 
> processing circuitry.
So, they deinterlace... Though they might to a better job since they've
got dedicated hardware for this.

> On Tue, Jul 29, 2008 at 01:43:51AM +0200, Roland Scheidegger wrote:
>> you ask me... Decent TV hardware should have at least VGA inputs, and
>> if
>> it's not CRT based it doesn't make sense in the first place...
> for building a linux based PAL satellite recorder SCART is still
> superior to VGA. That's why we want to play SCART over VGA. Of course 
> this changes if HDTV comes into play.
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
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).


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