Instal pra

I wouild like to install xpra for X11 windowing.

When I do the following I get an error:

apk add xpra --repository http://dl-3.alpinelinux.org/alpine/edge/testing/
ERROR: unsatisfiable constraints:
so:libavcodec.so.57 (missing):
required by: xpra-0.17.1-r1[so:libavcodec.so.57]
so:libavutil.so.55 (missing):
required by: xpra-0.17.1-r1[so:libavutil.so.55]
so:libswscale.so.4 (missing):
required by: xpra-0.17.1-r1[so:libswscale.so.4]
so:libvpx.so.3 (missing):
required by: xpra-0.17.1-r1[so:libvpx.so.3]
so:libwebp.so.6 (missing):
required by: xpra-0.17.1-r1[so:libwebp.so.6]
so:libx264.so.148 (missing):
required by: xpra-0.17.1-r1[so:libx264.so.148]
so:libx265.so.79 (missing):
required by: xpra-0.17.1-r1[so:libx265.so.79]
/