Ok, I know I am not the only one that could not get and install the lib*-ffmpeg-dev packages. But I have finally found working packages for Jessie!
first install libssh-gcrypt-4 (I used synaptic)
now download all these packages
libavcodec-dev_2.7.2-1_amd64.deb
libavcodec-ffmpeg56_2.7.2-1_amd64.deb
libavcodec-ffmpeg-dev_2.7.2-1_all.deb
libavdevice-dev_2.7.2-1_amd64.deb
libavdevice-ffmpeg56_2.7.2-1_amd64.deb
libavdevice-ffmpeg-dev_2.7.2-1_all.deb
libavfilter-dev_2.7.2-1_amd64.deb
libavfilter-ffmpeg5_2.7.2-1_amd64.deb
libavfilter-ffmpeg-dev_2.7.2-1_all.deb
libavformat-dev_2.7.2-1_amd64.deb
libavformat-ffmpeg56_2.7.2-1_amd64.deb
libavformat-ffmpeg-dev_2.7.2-1_all.deb
libavresample-dev_2.7.2-1_amd64.deb
libavresample-ffmpeg2_2.7.2-1_amd64.deb
libavresample-ffmpeg-dev_2.7.2-1_all.deb
libavutil-dev_2.7.2-1_amd64.deb
libavutil-ffmpeg54_2.7.2-1_amd64.deb
libavutil-ffmpeg-dev_2.7.2-1_all.deb
libpostproc-dev_2.7.2-1_amd64.deb
libpostproc-ffmpeg53_2.7.2-1_amd64.deb
libpostproc-ffmpeg-dev_2.7.2-1_all.deb
libswresample-dev_2.7.2-1_amd64.deb
libswresample-ffmpeg1_2.7.2-1_amd64.deb
libswresample-ffmpeg-dev_2.7.2-1_all.deb
libswscale-dev_2.7.2-1_amd64.deb
libswscale-ffmpeg3_2.7.2-1_amd64.deb
libswscale-ffmpeg-dev_2.7.2-1_all.deb
libx265-59_1.7-4_amd64.deb
from here:
https://e-tobi.net/vdr-experimental/pool-jessie/binary/backports/and install 1 at a time starting with the straight file, then -dev, then -ffmpeg-dev
you will have to go back and forth on a couple packages, but they all installed correctly and they all work as advertised!!