[gdal-dev] Fwd: [OpenJPEG] OpenJPEG 2.2.0 is out ! Faster and safer.

[Even Rouault]

On mardi 29 août 2017 01:42:21 CEST jratike80 wrote:
> N. Farah wrote
> 
> > The results you get when enabling multi-threading are very interesting:
> > 26.s to 9.9 s. Then using the work in progress you end up with 1s.
> > Basically a 26 times speed improvement.
> 
> Hi,
> 
> As always when you read benchmarks, you must keep the results and the
> context together so it is clear what was tested. In this case the important
> part is that the test applies to single tiled images. They are what Kakadu
> prefers (also in the usage examples) and it handles them splendidly by
> utilizing the precincts. OpenJPEG has not been able to use precincts
> (despite in a fork
> https://lists.osgeo.org/pipermail/gdal-dev/2016-February/043650.html) and
> therefore it has slow with single tiled images and actually useless if the
> tile size is something like 20000 by 20000 pixels.
> 
> Even can say how much faster the new branch is with JPEG2000 images which
> use 1024x1024 tiles but I suppose that the speed-up factor is much less than
> 26.

For tiled images, the GDAL OpenJPEG driver currently still read whole tiles (perhaps this 
should be re-considered at some point), so sub-tile decoding improvements will not help 
here, and you won't get more than the improvements done during 2.2.0, so something like 
20% for openjpeg single-threaded (your mileage may vary), or more if you enable 
OPJ_NUM_THREADS. 

Even

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