[gdal-dev] Open Jpeg 2.3.0 and OPJ_NUM_THREADS

[N. Farah]

Looking at https://trac.osgeo.org/gdal/browser/trunk/gdal/frmts/openjpeg/openjpegdataset.cpp?rev=40418


I now see the GDAL made changes to enable multi-threading.


Thanks

Noureddine Farah

________________________________
From: N. Farah <nfarah at hotmail.com>
Sent: Tuesday, October 31, 2017 3:50:15 PM
To: Even Rouault; gdal-dev at lists.osgeo.org
Subject: Re: [gdal-dev] Open Jpeg 2.3.0 and OPJ_NUM_THREADS


Thanks for the quick response. I'm not using latest GDAL and was curious where that multi-threading enabling was made ? Was it some where in GDAL code or through an option in the openjpeg 2.3.0 API ?


Thanks

Noureddine Farah

________________________________
From: Even Rouault <even.rouault at spatialys.com>
Sent: Tuesday, October 31, 2017 3:47:01 PM
To: gdal-dev at lists.osgeo.org
Cc: N. Farah
Subject: Re: [gdal-dev] Open Jpeg 2.3.0 and OPJ_NUM_THREADS


On mardi 31 octobre 2017 19:39:23 CET N. Farah wrote:

> Hi,

>

>

> In http://gdal.org/frmt_jp2openjpeg.html under 'Thread Support' section

> there is the following:

>

> "Starting with GDAL 2.3, this multi-threading at code-block level is

> automatically enabled by GDAL".

>

>

> Was meant "Starting with OpenJpeg 2.3, ..." ?



No, was meant starting with GDAL 2.3 (the current dev version). And that requires openjpeg >= 2.2 as well.



>

> If yes, was that enabling made in the 'OpenJpeg 2.3' library or was made in

> GDAL ?



openjpeg >= 2.2 (actually 2.1.2, but I restricted to 2.2 or later) brings multithreading decoding at codeblock level, and GDAL trunk automatically enables it.



So the doc is correct I think, but I know that those similar version numbers between GDAL and openjpeg can be confusing.



Bottom line: use the latest and greatest of both to get the better performance.



Even



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