[linux-dvb] Re: Choosing the "best" DVB-S premium card

[Holger Waechtler <holger@convergence.de>]

Michal Dobrzynski wrote:
> Thanks for the pointer.
>
> Unfortunately  the Loewe chassis I have doesn't like just about all  
> modelines. It takes literally hours and hours with the TV connected to  
> one output and a monitor connected to the other in mirroring mode (this  
> allows me to recover from going outside the limitations of the VGA  
> input for the thousandth time) to find valid modelines. As best as I  
> can tell they are all 60hz plus or minus 0.5hz or so.
The 50Hz modeline in the example is meant for TV outs, deinterlacing 
will get done automatically by the TV in this case.

If you use a 60Hz mode you need to deinterlace in software before, in 
this case you want to send VGA-like progressive pictures to your TV.

Note that common deinterlacers e.g. in mplayer and ffmpeg are of good 
quality (pause the picture to check the pure deinterlacer quality) but 
halve the temporal resolution since they usually only deinterlace 
bottom-field half pictures. This causes an effective framerate of 25Hz 
and visible flickering in running texts.

But implementing top-field deinterlacing is straightforward - the 
algorithm is the same, only the line offsets are different...

See the avpicture_deinterlace() implementation in 
http://www1.mplayerhq.hu/cgi-bin/cvsweb.cgi/ffmpeg/libavcodec/imgconvert.c?rev=1.50&content-type=text/x-cvsweb-markup&cvsroot=FFMpeg
for an example.

Holger



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