[noggin]

All Amlogic devices are limited to 16-bit output. An HDMI analyzer or a HDFury Vertex will show you the maximum word length (bit depth) set in the Channel Status Bits of the HDMI signal. 24-bit doesn't necessarily mean that the output is indeed 24-bit, but if these bits are set to 16-bit (max word length-20), then 24-bit output is completely ruled out and that is what you would see with Amlogic devices.

I have a post somewhere on LibreELEC forums on this topic. I recorded the HDMI output at 24-bit depth and then analyzed the real bit-depth of the output. It is only 16-bit for Amlogic devices.

Not true, actually. I can get Vero4k to output 24-bit LPCM. If there are problems interfacing with other equipment I'm sure OSMC can sort them out.   

Yes, indeed you can get 24-bit output from Amlogic SoCs with non-Android OS. The problem is incorrect word length in the channel status. Sinks that do not honor the channel status word length may process the signal as 24-bit.  

  
So does this mean AMLogic SoCs can output 24bit PCM audio over HDMI, but it isn't correctly flagged in the stream channel status as 24 bit ?.

Therefore ff a sink (like an AVR) looks at the raw audio data - it will see 24 bit audio and play it fine? If the sink looks at the accompanying channels status data it will see 16 bit audio and treat it as such?

Is this also possibly also related to the issue some AVRs have with DTD MA HRA streams?