Yes but that is i think not sutch a big problem than having no really plex option for 5.1 sound on these devices and all HIFI can decode that audi as is meant to do it.
Plex or Serenity have no control of the player, Amazon does as it is built into FireOS. But even with that 5.1 does work in MP4 containers. (At least AC3/eAC3)
A pass thgrough should not be so hard to do.
Again, see above. Amazon controls the standard player which has no passthrough, and then if you use an External player that player is responsible for the passthrough. But as I stated they are limited to how/what they can pass through as well due to FireOS/AndroidOS limitations.
And on FIRE TV u should hav the option to use FIBER is u realy want to get 7.1 pass through.
Are you referring to the optical out? Optical is limited to 5.1. To use 7.1 you have to use HDMI. However, once again the FireOS/AndroidOS limitations prevent that.
Dolby is only certified to HW players ans only some software i think in combination with HW such as power DVD on pc.
So if u can get it certified do it just mak it 10buks and fine until then the pass through should not be the probelem.
Dolby certification isn't only to HW players. Movie studios pay for Dolby Certification, Software players pay for it (Including Microsoft for Windows Media Player licenses), and many other things. Dolby doesn't release an actual pricelist so there is no telling how much it would cost. But that doesn't matter since Amazon is the one that controls/limits what the standard media player has the ability to do either decoding or passthrough. And if you're using an external player you need to talk to their development team about implementing passthrough/additional codecs.
And maybe u can tell me why to transcode anything for playing on firetv? (I mean the VIdeo) if u can handle the Videcodecs it should not be a problem too.
I don't know what you're asking here. If you think the FireTV can handle more than it is currently playing you can turn on ForceDirect Play. I have a feeling you're trying to compare the built in player against an external player which won't work as the external players all have extra software decoders that the default player does not which is why the server transcodes the files.