[FFmpeg-user] How can I extract 8 linear thumbnails from videos with differnt length?

[Christoph Gerstbauer]

Hi

I want to extract 8 thumbnails from every video I have which represents 
a linear "timeline" over the complete length (100percent) of the video.

Examples:
90min video: thumbnail at Minute 10, 20, 30, ... 80.
9min video: thumbnail at Minute 1, 2, 3, ... 8.
120min video: thumbnail at Minute 15, 30, 45, ... 105.

Is there a filter which can be used for that in combination with the 
-vframe command?
I want to use ONE command line, where the video length is used as 100 
percent.
And at every 11,1% (100/9) of the timeline I want to generate a thumbnail.
I dont need a thumbnail at 0 and 100% ;) because there is mostly black 
content.

Best Regards
Christoph