[vlc-devel] Re: [patch] Fixed source aspect ratio calculation

Derk-Jan Hartman hartman at videolan.org
Tue Oct 18 15:47:43 CEST 2005

On 18 okt 2005, at 14:32, Marian Durkovic wrote:
> On Tue, Oct 18, 2005 at 02:07:49AM -0700, Michel Lespinasse wrote:
>> On Tue, Oct 18, 2005 at 09:44:51AM +0200, Marian Durkovic wrote:
>>> This IMHO means, that VLC needs to immplement 1088->1080 fix,  
>>> otherwise
>>> the users will still complain about HDTV greyline bug on  
>>> considerable amount
>>> of HDTV content (claiming their STB played it fine so there must  
>>> be a "bug"
>>> in VLC). The problem is so widespread, that it's not possible to  
>>> ignore it,
>>> and if the situation changes in the future there's nothing easier  
>>> than to
>>> remove this ugly fix.
>> In my opinion it'd be much better to teach the rescaling code to do
>> nothing if the pixel aspect ratio is within 1% of being square.  
>> That way
>> you have a more general way of preserving quality without having to
>> mess with the stream parameters. (you still get the 8 gray lines  
>> though).
> Michel,
>   my primary focus is to get rid of those 8 grey (green,  
> alternating) lines
> which look terrible during dark scenes.
>   Also, the output format of 1920x1080 with aspect ratio 16:9 could be
> encoded in several ways, e.g.
> -  1920x1080, pixel aspect ratio 1:1 (square)
> -  1440x1080, pixel aspect ratio 4:3
> -  1280x1080, pixel aspect ratio 3:2
>   All those formats break and loose quality, if display_height says  
> 1088
> instead of 1080.
>   On the other hand, I'm not aware of any single reasonable format  
> really
> utilising 1088 lines and maintaning sane aspect ratios at the same  
> time.
> Thus I think that my 1088->1080 fix couldn't harm anything in real  
> life,
> although I agree it's an ugly fix (to a common encoder bug, though).

I still don't agree, but at the VERY LEAST, there should be an option  
to disable such an ugly hack.


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