[XviD-devel] Bframes quant ratio

[Christoph Lampert]

Hi,

does anyone know why people keep using a _ratio_ for bframe quantizers?

So why is the quantizer calculated by multiplying, not by adding?
E.g. a ratio of 200 means quant 2-> bquant 4, and quant 3 -> bquant 6,
fine. But 5->10 and 6 -> 12 is too much of a difference already in my
eyes. 

I think good encoding should stay in the area below quant 10. For higher
quant, there is hardly any gain in filesize anymore, but degrading
quality. I can't see why this should be different for Bframes. 
To achieve Bquant <=10 it would be useful to just use   
bquant = quant + something (something = 1,2,3), 
not bquant = quant * something

I'm asking because I am just doing tests for all quant, all max_bfraems,
all bquant_ratio and it seems that for low quantizers bframes behave
better than for large ones. This might be because of too large difference
between P and B frames. 

gruel

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