[noggin]

@wrxtasy
@noggin
In the latest kodi versions it has been disabled means that can only pass LPCM?

For LiveTV - mainline Kodi builds will decode Live TV AC3 2.0 and 5.1 to 2.0 and 5.1 PCM - and output this as per your audio settings for non-passthrough audio. If you have 2.0 channels as your setting you can enable AC3 transcoding to re-encode the decoded PCM back to AC3.

(If you are in the UK then Freeview HD doesn't use AC3, it uses AAC - and as AAC passthrough support is not widespread outside of Japan, and I'm not sure Kodi supports it, PCM decode or AC3 transcode are the only options anyway)

In my sony xf9005 android tv (where i have kodi leia installed) connected via hdmi to a/v unit i have to enable ac3 transcoding to have 5.1 detected. Why?

I have an XF9005 too (though I don't run Kodi on it). The XF9005 will only be able to output PCM 2.0 or AC3/DD (and possibly E-AC3/DD+ and DTS) because it uses ARC over HDMI or SPDIF over Toslink output which is bandwidth limited and can't support 5.1/7.1PCM or DTS HD MA/HRA or Dolby True HD passthrough.

Coreelec is one of that forks that enabled audio passtrough again on live tv?

Yes - it could well be. The removal of AC3 passthrough for Live TV was seen as an issue by some, so forks have reinstated it.