[Gdal-dev] GDAL and Kakadu JPEG2000 performances and quality

[Frank Warmerdam]

Julien Demaria wrote:
> First I try with kdu_compress include in binary package ok Kakadu 4.0.3 
> for Windows :
> time kdu_compress.exe -i RGB.bmp -o RGB_kakadu_compress.jp2 -rate 
> 2.85,2.85,2.85
> => 36 seconds

Julien,

I am a bit vague on some of the kdu_compress options, but my understanding
is that -rate 2.85 means produce 2.85 bits per pixel in the compressed file
which would be equivelent to a quality of roughly 35.  Are you sure the
comparison is equivelent?   Could I get the .jp2 files produced with
kdu_compress and gdal_translate?

Another aspect is that kakadu *may* be converting to YCbCr color space
which preserves values better than RGB which is the form GDAL will save
data as.


> Maybe this virtual tiling is the reason ?
> (I don't know how kdu_compress write the data...)

This is a read-side thing, and shouldn't have any effect.  Of course,
there are a huge number of options which can come into play for JPEG2000
compression, and some of the GDAL ones are no doubt different than the
kdu_compress defaults.


> PS : kakadu_compress print a warning :
> "Note:
> The default rate control policy for colour images employs visual (CSF)
> weighting factors. To minimize MSE instead, specify `-no_weights'."
> 
> What is it ?

I don't really know.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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