Chapters

You can force specific frametypes for chapters by using a qpfile. Create a text file with notepad.

The format of this file is simply (each with a space between the next):

Frame Number | Frame Type | Quantizer

e.g.

500 K -1

600 K -1

900 K -1

Frame numbers should be in ascending order. K stands for keyframe. All Quantizers should be set to -1 (automatic).

Add the following 

--qpfile QPFILE_NAME