[MPlayer-dev-eng] 2 pass encoding - need explanation

[Jonas Jermann]

On Sat, Feb 22, 2003 at 06:22:07PM -0500, D Richard Felker III wrote:
> > What about the encoding speed? Someone told me that it is the 
> > same for each quantizer (I doubt it). And what about quant=1? I 
> 
> Encoding speed should not be affected by quantizer directly. Of
> course, the quantizer will affect motion estimation some, so it may
> change a little, but shouldn't change too much.
> 
> > heard it shouldn't be used. Does this apply to 1. pass too?
> 
> It's probably safe to use q=1, but there's not much benefit and it can
> actually waste bits and reduce the quality if you use vqmin=1 with
> rate control.
> 
> > And do small differences off quantizers matter for the 
> > estimation anyway? It doesn't encode yet, so my common sense tells 
> > me it will almost be the same result.
> 
> Yes it does encode. The first pass encodes *and* collects statistics
> from the encode to use in better distributing bits/adjusting quantizer
> in the second pass. So it's beneficial for the stats to be good.

of course, but I always redirect it to /dev/null. Afaik it isn't 
used afterwards, therefore I used the expression "doesn't encode 
yet". Thx for the information!


Regards
    Jonas