[MPlayer-users] about different swscalers

[Reimar Döffinger]

Hello,
On Tue, Aug 21, 2007 at 11:07:14AM +0100, vdmsss wrote:
[...]
> Is such a big difference expected? Where does it arise from? It must  
> be that gaussian sheds quite a few details from the stream... More  
> precisely, it appears to blur the image very badly.

Actually the amount of information in the resulting image is about the
same for gaussian and lanczos, just with the later one it looks better
for some people (I personally find it looks horrible since once in a
while it will add some slight artefacts). The difference in bitrate is
because lanczos add some sharp borders which are very hard to encode
with the current algorithms, since they are intended for natural images
and quite unsuitable for the kind of "artefacts" some scalers create.
The nr lavcopts options might help reduce the effect a bit though.

> This discrepancy seems also to indicate that when working with  
> bitrate=N (rather than crf=Q) one should take the scaler into  
> account, eg not to throw wasted bits at the gaussian one. Or not?

It also means you should consider scaling with gaussian and running a
sharpening (or some other post-processing that helps in this case)
during playback.

Greetings,
Reimar Döffinger