[kraka40]

So is this correct?

FTV1 and FTV2 passthrough works, but due to concerns with Live feeds which requires finer tune controls of the active audio buffer the signal must be locally handled (decoded). Recorded content can be passed through without concern providing DD and DDP on the receiver. DTS is not supported by FTV.

Since FTV only supports a 2 channel PCM output signal due to crappy implementation of MediaCodec in FTV2 and non-standard implementation in FTV1, the signal needs to be transcoded back to an AC3 signal which is transmitted as a 2 channel signal, hence the requirement for a 2 speaker configuration, which in this case represents the PCM decoding capabilities of the Android hardware, not the receiver and speaker configuration.

Am I close?

Vendor firmware bugs
- Some Android TVs only support 384 kb/s AC3 and error out on 640 kb/s
- EAC3 7.1 is broken on all FireTV firmware. I suggest disabling EAC3 and use Dolby Transcoding _and_ speakers set to 2.0. It makes no sense to passthrough if you can output 6 or more PCM channels

Yes (on Android only: 640 kbit/s on all other OS including 25$ RPi). AC3 is lossy anyways. It makes zero sense to reencode a decoded signal back to AC3 just to see Dolby on the AVR display. But for those shitty boxes with just ARC output there is no alternative as they are limited to 2 PCM channels.