When I have transcoding set to hardware on my Kindle Fire I get audio only with no video. Hybrid seems to work, but I'm not sure why it's transcoding at all.
I spoke too soon. It isn't quite keeping up with live TV, Recordings do ok.
Whilst I don't have a Kindle Fire, on my Fire TV it is 'Decoding' - not 'Transcoding'.
I have to set Software, on my Fire TV Cubes, to use all channels reliably with UK FreeSat.
You are right. It's decoder. It seems to be working at about 80% of perfect for me on live streams and 95% on recorded content. Now I just need to figure out how to get the 5.1 audio downmixed to stereo.
I have a Surround Sound option, in the same place as the Decoding options, on my Fire TVs.
I believe hardware decoding is notoriously flakey on some Fire TV devices, perhaps this extends to the tablets as well, certainly a number of work arounds were required for the Sticks (from both Channels and upstream at Amazon) - I've never bothered to pursue it on the Cube, as software worked without issue.