[flac-dev] Retuning compression levels

[Erik de Castro Lopo]

Martijn van Beurden wrote:

> With the patch I mailed earlier today, I found out a few 
> adjustments could be made to the compression level settings.This 
> retuning speeds up the encoding and improves compression, while 
> not changing anything decoding-wise.
> 
> Currently, compression settings are as follows
> 
> -5, -l 8 -b 4096 -m -r 5 -A tukey(0.5)
> -6, -l 8 -b 4096 -m -r 6-A tukey(0.5)
> -7, -l 8 -b 4096 -m -e -r 6-A tukey(0.5)
> -8, -l 12 -b 4096 -m -e -r 6-A tukey(0.5)
> 
> I suggest the following, in case my previous patch is accepted
> 
> -5, -l 8 -b 4096 -m -r 5 -A tukey(0.5)
> -6, -l 8 -b 4096 -m -r 6-A tukey(0.5);partial_tukey(2)
> -7, -l 8 -b 4096 -m -r 6-A 
> tukey(0.5);partial_tukey(2);punchout_tukey(3)
> -8, -l 12 -b 4096 -m -r 6-A 
> tukey(0.5);partial_tukey(2);punchout_tukey(3)
> 
> See this graph for comparison:
> 
> http://www.audiograaf.nl/misc_stuff/setting-visualisation.pdf
> 
> This data was acquired with a reasonably large dataset (one 
> track from each album with which the comparison on 
> http://xiph.org/flac/comparison.html was made, so 43 tracks from 
> 43 different CDs), which I think is quite nicely balanced.
> 
> It looks like -6 will be almost as good as -8 is now, but much 
> faster. -7 will be a bit slower and -8 will be a bit faster, but 
> both will compress beter than -8 does now.


This all sounds great!

> I dropped -e because 
> it's compression improvement isn't worth the slowdown, but it is 
> easy for the user to add this anyway.

I think we should keep -e but may print a warning. The reason to keep it
is so that we do not break some random flac frontend that has this as
an option.

Cheers,
Erik
-- 
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Erik de Castro Lopo
http://www.mega-nerd.com/