[MPlayer-users] Re: encoding quality - bpp, resolution, quants and quality

Jonathan Rogers jonner at teegra.net
Tue Sep 9 12:11:14 CEST 2003

HR wrote:
> As the codecs get better and better, how true is the bpp recommandation
> table in encoding-tips.txt now and in the near future?

Those are just intended to be rules of thumb. I've encoded some stuff at 
less than 0.2 BPP which looked great and some stuff at greater than 0.25 
BPP that still had very noticeable artifacts. The minimum acceptable BPP 
varies hugely with quality and type of source material, quality of 
decoder and screen, and especially with the observer.

> I recently encoded a DVD (dungeons and dragons) to a 700MB XViD,
> downscaling for a decent AR and a bpp of 0.199. The result looks quite
> decent, but reviewing the 2pass log, I notice that ALL frames got a
> quant of 2. I should propably scale it up a bit then, but how can it be
> that ALL the quants = 2?

That does seem odd. Was the resulting BPP really 0.199? In the end, all 
that matters is perception. Try a larger frame size and see if it still 
looks OK. Video encoders are still pretty stupid. Only a human can truly 
judge visual quality.

Jonathan Rogers

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