slow batch conversion

fotografie fotografie at
Sun Aug 20 11:00:57 BST 2017


thanks for the answer.

Let me give a short overview of what I did (digikam 5.6 and earlier) and
where my fault was:
- i selected the pics for batch conversion
- in batch conversion at the bottom you have the batch conversion tabs
and the control list.
- in the tab named "behaviour" (or so, I use the german version,
therefore I don't know whether the name is correct) there you can
select: "use multicore" - and that I did not do, so the process of
converting 500 pics was slowed down.

Have a good week

Am 20.08.2017 um 11:03 schrieb Gilles Caulier:
> Hi,
> There are few explanation to give here about multi threading.
> In digiKam all is multi-threaded when this can be and when it's give
> improvements of speed :
> - mostly all image editor tools use multi-core.
> - mostly all BQM tools use multi-core (same code than editor in fact).
> - BQM queue can be multi-threaded (more than one at the same time).
> One core or multi-core (optional)
> - Maintenance tools : same as BQM queue.
> - The database access is now ported to multi-cores/multi-threads (KIO
> slaves was used before). It use always all core to process, but some
> bottleneck can appear with database if too much query are queue in
> interface, especially with sqlite. Mysql is better in this case.
> - Face management use multi-core or not.
> - Assistants as panorama, emailimages, pseudoHDR, HTMLGallery,
> Videoslideshow : all are mutithreaded, and some tools use multi-core,
> some not, as videoslideshow which serialize a video flux from images
> (encoding with ffmpeg use multicore).
> What do not use multicore :
> - Scan items : even if it run in a separated thread, it do not use
> multicores yet.
> - Download items from camera : there is a bottleneck with concurrent
> media access. It use a separate thread at least.
> Note there is a bug about multi-core support fixed in next 5.7.0 which
> can introduce huge time latency in previous versions. This fix is a
> big step in stabilization of application.
> Best
> Gilles Caulier
> 2017-08-20 0:03 GMT+02:00 fotografie <fotografie at>:
>> Hello,,
>> I had the same problem with digikan 5.4.
>> The batch converison worked really slow. But I found an entry in the
>> menu to tell digikam to use all prozessor kernels. And that speeded it
>> up. Now I have the problem again with digikam 5.6 and 5.7. Where can I
>> set digkam up to use all cpus?
>> Thanks in advance for your help.
>> Best regards Ulf

Mit freundlichem Gruß 

Ulf Richter 

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