[mythtv] Feasability of using software scalers in mythtv videoout

Ed W lists at wildgooses.com
Thu May 11 19:56:31 UTC 2006


>Ignore the jpeg artifacts, the pngs were a meg each, but note how much 
>better picture quality you can get with the software scaler.

I only have a standard def TV, but I did similar experiments using 
mplayer's software video output and came to the same conclusion as you.  
Lanczos and bicubic splines are a pretty decent step up in quality 
giving a sharper image (which doesn't look artificially sharpened). 

Theoretically Lanczos is a mathematically more correct scaler (ie nearer 
optimal), but in the literature it's often considered to be slightly 
bettered by bicubic splines apparently because the artifacts (such that 
there are) are more pleasing to the eye.  However, to my eye both were 
excellent and Lanczos was slightly sharper.

A good while back I hacked the software scaler in Myth to work for live 
tv and although I didn't persue it to the point that it would play tv 
smoothly it was clearly far better quality than the XV resize on my 
NVidia 5200 card. 

MPlayer would be a good point to start to examine the software playback 
scalers since nothing is allowed into the mplayer code which has the 
slightest bit of fat on it, so I should think their implementation is 
pretty decent.

Good luck!

Ed W

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