I am having difficulties to make Gimp accept my specs concerning the delay time of the layers in the only animated background image I really need.

It looks like Gimp does not allow each layer to have its own delay time, different than the others, may be except for the background layer. I have been trying to work out what this rule is but with no success, the result appears to be all over the place and I cannot find anything on Google about this subject.

What I am trying to do is an animated image with 4 layers:
one layer delay time 300ms
next layer delay time 1000ms (blank layer)
next layer delay time 300ms
next layer delay time 1000ms (blank layer)
looping continuously, any layer can be the background as far as I am concerned.

It does not matter how I organize it, Gimp changes the values of one or more layers. For example replacing each layer that has a delay of 1000ms with 3 consecutive layers of 300ms each, to make them all 300ms, does not look acceptable to Gimp and a layer of 1000ms in the middle is changed to 300ms.

The blank layers were only inserted to restore the CPU time used by the animation from over 99% on a 19" LCD monitor to an acceptable level and it works (they enhance the animation rather than distort it).

Perhaps there is a better approach.

Can anyone explain what the problem is?

Thank you for your help.

Use GAP - the Gimp Animation Plugin.

(Or Image Magick's "animate" )

Gap was already used to specify the delay values and is probably the part of the software whose rules I cannot work out. Gimp 2 seems to have it incorporated.

$animate myfile.gif -delay 900
does not work, it looks like the values determined in Gimp/Gap prevail when the animation is performed under ImageMagick, it also looks like even if it accepted other values, there is no option to save them.