huge rendering time for concatenated files

rendering a concatenated files takes a lot of time compared to rendering items individually

For example, ISM1 to binaural takes:

21 sec for a concatenated signal of 6 items 52 sec for a concatenated signal of 12 items 168 sec for a concatenated signal of 24 items 358 sec for a concatenated signal of 36 items

So for an experiment like ISM1 where we need the external render for 20 conditions. It means the processing time for the experiment will be more than 3 hours.

while it takes less than 30 secondes to rendered the 36 items when they are not concatenated (less than 10 minutes for the 20 conditions)

I'm using pythons under dos, not sure if that makes any difference.

@treffehn, Would it be possible to inverse the sequence of operations and do the splitting before the rendering? or is there any thing I can do locally to speed up the process on the concactenated files?

Thank you!