[SOLVED] Unable to install libav-tools, ffmpeg etc. on Stretch

[Gyuunduh]

I just updated debian/xbian to Stretch but am now missing avconv which is a part of libav-tools package. When trying to install it, apt-get tells me

Code:

xbian@RPi2 ~ $ sudo apt-get install libav-tools
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
libav-tools : Depends: ffmpeg but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

When trying to install ffmpeg the error message is a bit more precise:

Code:

sudo apt-get install ffmpeg
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
ffmpeg : Depends: libavdevice57 (>= 7:3.2.5) but it is not going to be installed
          Depends: libsdl2-2.0-0 (>= 2.0.4) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

And on and on, with libavdevice57 the end of failed installation error message being

Code:

The following information may help to resolve the situation:

The following packages have unmet dependencies:
libavdevice57 : Depends: libsdl2-2.0-0 (>= 2.0.4) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

Any ideas how to fix this and get libav-tools installed?